Dynamic Proxy revisit
Dynamic Proxy in JDK
Proxy is a class which can get the proxy class and create the proxy instance. It has a private default constructor and a protected constructor with a contractor argument: InvocationHandler.
InvocationHandler is an interface which we can apply our code into the generated proxy class. It has only one method: Object invoke(Object proxy, Method method, Object[] args)
Proxy has four static methods:
static Class<?> getProxyClass(ClassLoader loader, Class<?>... interfaces)
static Object newProxyInstance(ClassLoader loader, Class<?>[] interfaces, InvocationHandler h)
static boolean isProxyClass(Class<?> cl)
static InvocationHandler getInvocationHandler(Object proxy)
Now let us see how to generate a proxy class in memory. The main logic is in ProxyClassFactory: firstly it call the ProxyGenerator.generateProxyClass(proxyName, interfaces, accessFlags) to generate the bytes of class file, and then it invokes the native method of Proxy static native Class<?> defineClass0(ClassLoader loader, String name, byte[] b, int off, int len) to load and resolve the bytes into a Class.
So the two static methods ProxyGenerator.generateProxyClass(..) and Proxy.defineClass0(..) are very important.
Proxy.defineClass0(..) makes that we don’t need to define a ClassLoader to load a class from raw bytes. We will use it as a utility method later.
ProxyGenerator has no secret since it just generates the bytecode following the class file format in the JVM specification.
// https://github.com/openjdk-mirror/jdk7u-jdk/blob/master/src/share/classes/sun/misc/ProxyGenerator.java
package sun.misc;
import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.lang.reflect.Array;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;
import sun.security.action.GetBooleanAction;
/**
* ProxyGenerator contains the code to generate a dynamic proxy class
* for the java.lang.reflect.Proxy API.
*
* The external interfaces to ProxyGenerator is the static
* "generateProxyClass" method.
*
* @author Peter Jones
* @since 1.3
*/
public class ProxyGenerator {
/*
* In the comments below, "JVMS" refers to The Java Virtual Machine
* Specification Second Edition and "JLS" refers to the original
* version of The Java Language Specification, unless otherwise
* specified.
*/
/* generate 1.5-era class file version */
private static final int CLASSFILE_MAJOR_VERSION = 49;
private static final int CLASSFILE_MINOR_VERSION = 0;
/*
* beginning of constants copied from
* sun.tools.java.RuntimeConstants (which no longer exists):
*/
/* constant pool tags */
private static final int CONSTANT_UTF8 = 1;
private static final int CONSTANT_UNICODE = 2;
private static final int CONSTANT_INTEGER = 3;
private static final int CONSTANT_FLOAT = 4;
private static final int CONSTANT_LONG = 5;
private static final int CONSTANT_DOUBLE = 6;
private static final int CONSTANT_CLASS = 7;
private static final int CONSTANT_STRING = 8;
private static final int CONSTANT_FIELD = 9;
private static final int CONSTANT_METHOD = 10;
private static final int CONSTANT_INTERFACEMETHOD = 11;
private static final int CONSTANT_NAMEANDTYPE = 12;
/* access and modifier flags */
private static final int ACC_PUBLIC = 0x00000001;
private static final int ACC_PRIVATE = 0x00000002;
// private static final int ACC_PROTECTED = 0x00000004;
private static final int ACC_STATIC = 0x00000008;
private static final int ACC_FINAL = 0x00000010;
// private static final int ACC_SYNCHRONIZED = 0x00000020;
// private static final int ACC_VOLATILE = 0x00000040;
// private static final int ACC_TRANSIENT = 0x00000080;
// private static final int ACC_NATIVE = 0x00000100;
// private static final int ACC_INTERFACE = 0x00000200;
// private static final int ACC_ABSTRACT = 0x00000400;
private static final int ACC_SUPER = 0x00000020;
// private static final int ACC_STRICT = 0x00000800;
/* opcodes */
// private static final int opc_nop = 0;
private static final int opc_aconst_null = 1;
// private static final int opc_iconst_m1 = 2;
private static final int opc_iconst_0 = 3;
// private static final int opc_iconst_1 = 4;
// private static final int opc_iconst_2 = 5;
// private static final int opc_iconst_3 = 6;
// private static final int opc_iconst_4 = 7;
// private static final int opc_iconst_5 = 8;
// private static final int opc_lconst_0 = 9;
// private static final int opc_lconst_1 = 10;
// private static final int opc_fconst_0 = 11;
// private static final int opc_fconst_1 = 12;
// private static final int opc_fconst_2 = 13;
// private static final int opc_dconst_0 = 14;
// private static final int opc_dconst_1 = 15;
private static final int opc_bipush = 16;
private static final int opc_sipush = 17;
private static final int opc_ldc = 18;
private static final int opc_ldc_w = 19;
// private static final int opc_ldc2_w = 20;
private static final int opc_iload = 21;
private static final int opc_lload = 22;
private static final int opc_fload = 23;
private static final int opc_dload = 24;
private static final int opc_aload = 25;
private static final int opc_iload_0 = 26;
// private static final int opc_iload_1 = 27;
// private static final int opc_iload_2 = 28;
// private static final int opc_iload_3 = 29;
private static final int opc_lload_0 = 30;
// private static final int opc_lload_1 = 31;
// private static final int opc_lload_2 = 32;
// private static final int opc_lload_3 = 33;
private static final int opc_fload_0 = 34;
// private static final int opc_fload_1 = 35;
// private static final int opc_fload_2 = 36;
// private static final int opc_fload_3 = 37;
private static final int opc_dload_0 = 38;
// private static final int opc_dload_1 = 39;
// private static final int opc_dload_2 = 40;
// private static final int opc_dload_3 = 41;
private static final int opc_aload_0 = 42;
// private static final int opc_aload_1 = 43;
// private static final int opc_aload_2 = 44;
// private static final int opc_aload_3 = 45;
// private static final int opc_iaload = 46;
// private static final int opc_laload = 47;
// private static final int opc_faload = 48;
// private static final int opc_daload = 49;
// private static final int opc_aaload = 50;
// private static final int opc_baload = 51;
// private static final int opc_caload = 52;
// private static final int opc_saload = 53;
// private static final int opc_istore = 54;
// private static final int opc_lstore = 55;
// private static final int opc_fstore = 56;
// private static final int opc_dstore = 57;
private static final int opc_astore = 58;
// private static final int opc_istore_0 = 59;
// private static final int opc_istore_1 = 60;
// private static final int opc_istore_2 = 61;
// private static final int opc_istore_3 = 62;
// private static final int opc_lstore_0 = 63;
// private static final int opc_lstore_1 = 64;
// private static final int opc_lstore_2 = 65;
// private static final int opc_lstore_3 = 66;
// private static final int opc_fstore_0 = 67;
// private static final int opc_fstore_1 = 68;
// private static final int opc_fstore_2 = 69;
// private static final int opc_fstore_3 = 70;
// private static final int opc_dstore_0 = 71;
// private static final int opc_dstore_1 = 72;
// private static final int opc_dstore_2 = 73;
// private static final int opc_dstore_3 = 74;
private static final int opc_astore_0 = 75;
// private static final int opc_astore_1 = 76;
// private static final int opc_astore_2 = 77;
// private static final int opc_astore_3 = 78;
// private static final int opc_iastore = 79;
// private static final int opc_lastore = 80;
// private static final int opc_fastore = 81;
// private static final int opc_dastore = 82;
private static final int opc_aastore = 83;
// private static final int opc_bastore = 84;
// private static final int opc_castore = 85;
// private static final int opc_sastore = 86;
private static final int opc_pop = 87;
// private static final int opc_pop2 = 88;
private static final int opc_dup = 89;
// private static final int opc_dup_x1 = 90;
// private static final int opc_dup_x2 = 91;
// private static final int opc_dup2 = 92;
// private static final int opc_dup2_x1 = 93;
// private static final int opc_dup2_x2 = 94;
// private static final int opc_swap = 95;
// private static final int opc_iadd = 96;
// private static final int opc_ladd = 97;
// private static final int opc_fadd = 98;
// private static final int opc_dadd = 99;
// private static final int opc_isub = 100;
// private static final int opc_lsub = 101;
// private static final int opc_fsub = 102;
// private static final int opc_dsub = 103;
// private static final int opc_imul = 104;
// private static final int opc_lmul = 105;
// private static final int opc_fmul = 106;
// private static final int opc_dmul = 107;
// private static final int opc_idiv = 108;
// private static final int opc_ldiv = 109;
// private static final int opc_fdiv = 110;
// private static final int opc_ddiv = 111;
// private static final int opc_irem = 112;
// private static final int opc_lrem = 113;
// private static final int opc_frem = 114;
// private static final int opc_drem = 115;
// private static final int opc_ineg = 116;
// private static final int opc_lneg = 117;
// private static final int opc_fneg = 118;
// private static final int opc_dneg = 119;
// private static final int opc_ishl = 120;
// private static final int opc_lshl = 121;
// private static final int opc_ishr = 122;
// private static final int opc_lshr = 123;
// private static final int opc_iushr = 124;
// private static final int opc_lushr = 125;
// private static final int opc_iand = 126;
// private static final int opc_land = 127;
// private static final int opc_ior = 128;
// private static final int opc_lor = 129;
// private static final int opc_ixor = 130;
// private static final int opc_lxor = 131;
// private static final int opc_iinc = 132;
// private static final int opc_i2l = 133;
// private static final int opc_i2f = 134;
// private static final int opc_i2d = 135;
// private static final int opc_l2i = 136;
// private static final int opc_l2f = 137;
// private static final int opc_l2d = 138;
// private static final int opc_f2i = 139;
// private static final int opc_f2l = 140;
// private static final int opc_f2d = 141;
// private static final int opc_d2i = 142;
// private static final int opc_d2l = 143;
// private static final int opc_d2f = 144;
// private static final int opc_i2b = 145;
// private static final int opc_i2c = 146;
// private static final int opc_i2s = 147;
// private static final int opc_lcmp = 148;
// private static final int opc_fcmpl = 149;
// private static final int opc_fcmpg = 150;
// private static final int opc_dcmpl = 151;
// private static final int opc_dcmpg = 152;
// private static final int opc_ifeq = 153;
// private static final int opc_ifne = 154;
// private static final int opc_iflt = 155;
// private static final int opc_ifge = 156;
// private static final int opc_ifgt = 157;
// private static final int opc_ifle = 158;
// private static final int opc_if_icmpeq = 159;
// private static final int opc_if_icmpne = 160;
// private static final int opc_if_icmplt = 161;
// private static final int opc_if_icmpge = 162;
// private static final int opc_if_icmpgt = 163;
// private static final int opc_if_icmple = 164;
// private static final int opc_if_acmpeq = 165;
// private static final int opc_if_acmpne = 166;
// private static final int opc_goto = 167;
// private static final int opc_jsr = 168;
// private static final int opc_ret = 169;
// private static final int opc_tableswitch = 170;
// private static final int opc_lookupswitch = 171;
private static final int opc_ireturn = 172;
private static final int opc_lreturn = 173;
private static final int opc_freturn = 174;
private static final int opc_dreturn = 175;
private static final int opc_areturn = 176;
private static final int opc_return = 177;
private static final int opc_getstatic = 178;
private static final int opc_putstatic = 179;
private static final int opc_getfield = 180;
// private static final int opc_putfield = 181;
private static final int opc_invokevirtual = 182;
private static final int opc_invokespecial = 183;
private static final int opc_invokestatic = 184;
private static final int opc_invokeinterface = 185;
private static final int opc_new = 187;
// private static final int opc_newarray = 188;
private static final int opc_anewarray = 189;
// private static final int opc_arraylength = 190;
private static final int opc_athrow = 191;
private static final int opc_checkcast = 192;
// private static final int opc_instanceof = 193;
// private static final int opc_monitorenter = 194;
// private static final int opc_monitorexit = 195;
private static final int opc_wide = 196;
// private static final int opc_multianewarray = 197;
// private static final int opc_ifnull = 198;
// private static final int opc_ifnonnull = 199;
// private static final int opc_goto_w = 200;
// private static final int opc_jsr_w = 201;
// end of constants copied from sun.tools.java.RuntimeConstants
/** name of the superclass of proxy classes */
private final static String superclassName = "java/lang/reflect/Proxy";
/** name of field for storing a proxy instance's invocation handler */
private final static String handlerFieldName = "h";
/** debugging flag for saving generated class files */
private final static boolean saveGeneratedFiles =
java.security.AccessController.doPrivileged(
new GetBooleanAction(
"sun.misc.ProxyGenerator.saveGeneratedFiles")).booleanValue();
/**
* Generate a proxy class given a name and a list of proxy interfaces.
*/
public static byte[] generateProxyClass(final String name,
Class[] interfaces)
{
ProxyGenerator gen = new ProxyGenerator(name, interfaces);
final byte[] classFile = gen.generateClassFile();
if (saveGeneratedFiles) {
java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction<Void>() {
public Void run() {
try {
FileOutputStream file =
new FileOutputStream(dotToSlash(name) + ".class");
file.write(classFile);
file.close();
return null;
} catch (IOException e) {
throw new InternalError(
"I/O exception saving generated file: " + e);
}
}
});
}
return classFile;
}
/* preloaded Method objects for methods in java.lang.Object */
private static Method hashCodeMethod;
private static Method equalsMethod;
private static Method toStringMethod;
static {
try {
hashCodeMethod = Object.class.getMethod("hashCode");
equalsMethod =
Object.class.getMethod("equals", new Class[] { Object.class });
toStringMethod = Object.class.getMethod("toString");
} catch (NoSuchMethodException e) {
throw new NoSuchMethodError(e.getMessage());
}
}
/** name of proxy class */
private String className;
/** proxy interfaces */
private Class[] interfaces;
/** constant pool of class being generated */
private ConstantPool cp = new ConstantPool();
/** FieldInfo struct for each field of generated class */
private List<FieldInfo> fields = new ArrayList<FieldInfo>();
/** MethodInfo struct for each method of generated class */
private List<MethodInfo> methods = new ArrayList<MethodInfo>();
/**
* maps method signature string to list of ProxyMethod objects for
* proxy methods with that signature
*/
private Map<String, List<ProxyMethod>> proxyMethods =
new HashMap<String,List<ProxyMethod>>();
/** count of ProxyMethod objects added to proxyMethods */
private int proxyMethodCount = 0;
/**
* Construct a ProxyGenerator to generate a proxy class with the
* specified name and for the given interfaces.
*
* A ProxyGenerator object contains the state for the ongoing
* generation of a particular proxy class.
*/
private ProxyGenerator(String className, Class[] interfaces) {
this.className = className;
this.interfaces = interfaces;
}
/**
* Generate a class file for the proxy class. This method drives the
* class file generation process.
*/
private byte[] generateClassFile() {
/* ============================================================
* Step 1: Assemble ProxyMethod objects for all methods to
* generate proxy dispatching code for.
*/
/*
* Record that proxy methods are needed for the hashCode, equals,
* and toString methods of java.lang.Object. This is done before
* the methods from the proxy interfaces so that the methods from
* java.lang.Object take precedence over duplicate methods in the
* proxy interfaces.
*/
addProxyMethod(hashCodeMethod, Object.class);
addProxyMethod(equalsMethod, Object.class);
addProxyMethod(toStringMethod, Object.class);
/*
* Now record all of the methods from the proxy interfaces, giving
* earlier interfaces precedence over later ones with duplicate
* methods.
*/
for (int i = 0; i < interfaces.length; i++) {
Method[] methods = interfaces[i].getMethods();
for (int j = 0; j < methods.length; j++) {
addProxyMethod(methods[j], interfaces[i]);
}
}
/*
* For each set of proxy methods with the same signature,
* verify that the methods' return types are compatible.
*/
for (List<ProxyMethod> sigmethods : proxyMethods.values()) {
checkReturnTypes(sigmethods);
}
/* ============================================================
* Step 2: Assemble FieldInfo and MethodInfo structs for all of
* fields and methods in the class we are generating.
*/
try {
methods.add(generateConstructor());
for (List<ProxyMethod> sigmethods : proxyMethods.values()) {
for (ProxyMethod pm : sigmethods) {
// add static field for method's Method object
fields.add(new FieldInfo(pm.methodFieldName,
"Ljava/lang/reflect/Method;",
ACC_PRIVATE | ACC_STATIC));
// generate code for proxy method and add it
methods.add(pm.generateMethod());
}
}
methods.add(generateStaticInitializer());
} catch (IOException e) {
throw new InternalError("unexpected I/O Exception");
}
if (methods.size() > 65535) {
throw new IllegalArgumentException("method limit exceeded");
}
if (fields.size() > 65535) {
throw new IllegalArgumentException("field limit exceeded");
}
/* ============================================================
* Step 3: Write the final class file.
*/
/*
* Make sure that constant pool indexes are reserved for the
* following items before starting to write the final class file.
*/
cp.getClass(dotToSlash(className));
cp.getClass(superclassName);
for (int i = 0; i < interfaces.length; i++) {
cp.getClass(dotToSlash(interfaces[i].getName()));
}
/*
* Disallow new constant pool additions beyond this point, since
* we are about to write the final constant pool table.
*/
cp.setReadOnly();
ByteArrayOutputStream bout = new ByteArrayOutputStream();
DataOutputStream dout = new DataOutputStream(bout);
try {
/*
* Write all the items of the "ClassFile" structure.
* See JVMS section 4.1.
*/
// u4 magic;
dout.writeInt(0xCAFEBABE);
// u2 minor_version;
dout.writeShort(CLASSFILE_MINOR_VERSION);
// u2 major_version;
dout.writeShort(CLASSFILE_MAJOR_VERSION);
cp.write(dout); // (write constant pool)
// u2 access_flags;
dout.writeShort(ACC_PUBLIC | ACC_FINAL | ACC_SUPER);
// u2 this_class;
dout.writeShort(cp.getClass(dotToSlash(className)));
// u2 super_class;
dout.writeShort(cp.getClass(superclassName));
// u2 interfaces_count;
dout.writeShort(interfaces.length);
// u2 interfaces[interfaces_count];
for (int i = 0; i < interfaces.length; i++) {
dout.writeShort(cp.getClass(
dotToSlash(interfaces[i].getName())));
}
// u2 fields_count;
dout.writeShort(fields.size());
// field_info fields[fields_count];
for (FieldInfo f : fields) {
f.write(dout);
}
// u2 methods_count;
dout.writeShort(methods.size());
// method_info methods[methods_count];
for (MethodInfo m : methods) {
m.write(dout);
}
// u2 attributes_count;
dout.writeShort(0); // (no ClassFile attributes for proxy classes)
} catch (IOException e) {
throw new InternalError("unexpected I/O Exception");
}
return bout.toByteArray();
}
/**
* Add another method to be proxied, either by creating a new
* ProxyMethod object or augmenting an old one for a duplicate
* method.
*
* "fromClass" indicates the proxy interface that the method was
* found through, which may be different from (a subinterface of)
* the method's "declaring class". Note that the first Method
* object passed for a given name and descriptor identifies the
* Method object (and thus the declaring class) that will be
* passed to the invocation handler's "invoke" method for a given
* set of duplicate methods.
*/
private void addProxyMethod(Method m, Class fromClass) {
String name = m.getName();
Class[] parameterTypes = m.getParameterTypes();
Class returnType = m.getReturnType();
Class[] exceptionTypes = m.getExceptionTypes();
String sig = name + getParameterDescriptors(parameterTypes);
List<ProxyMethod> sigmethods = proxyMethods.get(sig);
if (sigmethods != null) {
for (ProxyMethod pm : sigmethods) {
if (returnType == pm.returnType) {
/*
* Found a match: reduce exception types to the
* greatest set of exceptions that can thrown
* compatibly with the throws clauses of both
* overridden methods.
*/
List<Class<?>> legalExceptions = new ArrayList<Class<?>>();
collectCompatibleTypes(
exceptionTypes, pm.exceptionTypes, legalExceptions);
collectCompatibleTypes(
pm.exceptionTypes, exceptionTypes, legalExceptions);
pm.exceptionTypes = new Class[legalExceptions.size()];
pm.exceptionTypes =
legalExceptions.toArray(pm.exceptionTypes);
return;
}
}
} else {
sigmethods = new ArrayList<ProxyMethod>(3);
proxyMethods.put(sig, sigmethods);
}
sigmethods.add(new ProxyMethod(name, parameterTypes, returnType,
exceptionTypes, fromClass));
}
/**
* For a given set of proxy methods with the same signature, check
* that their return types are compatible according to the Proxy
* specification.
*
* Specifically, if there is more than one such method, then all
* of the return types must be reference types, and there must be
* one return type that is assignable to each of the rest of them.
*/
private static void checkReturnTypes(List<ProxyMethod> methods) {
/*
* If there is only one method with a given signature, there
* cannot be a conflict. This is the only case in which a
* primitive (or void) return type is allowed.
*/
if (methods.size() < 2) {
return;
}
/*
* List of return types that are not yet known to be
* assignable from ("covered" by) any of the others.
*/
LinkedList<Class<?>> uncoveredReturnTypes = new LinkedList<Class<?>>();
nextNewReturnType:
for (ProxyMethod pm : methods) {
Class<?> newReturnType = pm.returnType;
if (newReturnType.isPrimitive()) {
throw new IllegalArgumentException(
"methods with same signature " +
getFriendlyMethodSignature(pm.methodName,
pm.parameterTypes) +
" but incompatible return types: " +
newReturnType.getName() + " and others");
}
boolean added = false;
/*
* Compare the new return type to the existing uncovered
* return types.
*/
ListIterator<Class<?>> liter = uncoveredReturnTypes.listIterator();
while (liter.hasNext()) {
Class<?> uncoveredReturnType = liter.next();
/*
* If an existing uncovered return type is assignable
* to this new one, then we can forget the new one.
*/
if (newReturnType.isAssignableFrom(uncoveredReturnType)) {
assert !added;
continue nextNewReturnType;
}
/*
* If the new return type is assignable to an existing
* uncovered one, then should replace the existing one
* with the new one (or just forget the existing one,
* if the new one has already be put in the list).
*/
if (uncoveredReturnType.isAssignableFrom(newReturnType)) {
// (we can assume that each return type is unique)
if (!added) {
liter.set(newReturnType);
added = true;
} else {
liter.remove();
}
}
}
/*
* If we got through the list of existing uncovered return
* types without an assignability relationship, then add
* the new return type to the list of uncovered ones.
*/
if (!added) {
uncoveredReturnTypes.add(newReturnType);
}
}
/*
* We shouldn't end up with more than one return type that is
* not assignable from any of the others.
*/
if (uncoveredReturnTypes.size() > 1) {
ProxyMethod pm = methods.get(0);
throw new IllegalArgumentException(
"methods with same signature " +
getFriendlyMethodSignature(pm.methodName, pm.parameterTypes) +
" but incompatible return types: " + uncoveredReturnTypes);
}
}
/**
* A FieldInfo object contains information about a particular field
* in the class being generated. The class mirrors the data items of
* the "field_info" structure of the class file format (see JVMS 4.5).
*/
private class FieldInfo {
public int accessFlags;
public String name;
public String descriptor;
public FieldInfo(String name, String descriptor, int accessFlags) {
this.name = name;
this.descriptor = descriptor;
this.accessFlags = accessFlags;
/*
* Make sure that constant pool indexes are reserved for the
* following items before starting to write the final class file.
*/
cp.getUtf8(name);
cp.getUtf8(descriptor);
}
public void write(DataOutputStream out) throws IOException {
/*
* Write all the items of the "field_info" structure.
* See JVMS section 4.5.
*/
// u2 access_flags;
out.writeShort(accessFlags);
// u2 name_index;
out.writeShort(cp.getUtf8(name));
// u2 descriptor_index;
out.writeShort(cp.getUtf8(descriptor));
// u2 attributes_count;
out.writeShort(0); // (no field_info attributes for proxy classes)
}
}
/**
* An ExceptionTableEntry object holds values for the data items of
* an entry in the "exception_table" item of the "Code" attribute of
* "method_info" structures (see JVMS 4.7.3).
*/
private static class ExceptionTableEntry {
public short startPc;
public short endPc;
public short handlerPc;
public short catchType;
public ExceptionTableEntry(short startPc, short endPc,
short handlerPc, short catchType)
{
this.startPc = startPc;
this.endPc = endPc;
this.handlerPc = handlerPc;
this.catchType = catchType;
}
};
/**
* A MethodInfo object contains information about a particular method
* in the class being generated. This class mirrors the data items of
* the "method_info" structure of the class file format (see JVMS 4.6).
*/
private class MethodInfo {
public int accessFlags;
public String name;
public String descriptor;
public short maxStack;
public short maxLocals;
public ByteArrayOutputStream code = new ByteArrayOutputStream();
public List<ExceptionTableEntry> exceptionTable =
new ArrayList<ExceptionTableEntry>();
public short[] declaredExceptions;
public MethodInfo(String name, String descriptor, int accessFlags) {
this.name = name;
this.descriptor = descriptor;
this.accessFlags = accessFlags;
/*
* Make sure that constant pool indexes are reserved for the
* following items before starting to write the final class file.
*/
cp.getUtf8(name);
cp.getUtf8(descriptor);
cp.getUtf8("Code");
cp.getUtf8("Exceptions");
}
public void write(DataOutputStream out) throws IOException {
/*
* Write all the items of the "method_info" structure.
* See JVMS section 4.6.
*/
// u2 access_flags;
out.writeShort(accessFlags);
// u2 name_index;
out.writeShort(cp.getUtf8(name));
// u2 descriptor_index;
out.writeShort(cp.getUtf8(descriptor));
// u2 attributes_count;
out.writeShort(2); // (two method_info attributes:)
// Write "Code" attribute. See JVMS section 4.7.3.
// u2 attribute_name_index;
out.writeShort(cp.getUtf8("Code"));
// u4 attribute_length;
out.writeInt(12 + code.size() + 8 * exceptionTable.size());
// u2 max_stack;
out.writeShort(maxStack);
// u2 max_locals;
out.writeShort(maxLocals);
// u2 code_length;
out.writeInt(code.size());
// u1 code[code_length];
code.writeTo(out);
// u2 exception_table_length;
out.writeShort(exceptionTable.size());
for (ExceptionTableEntry e : exceptionTable) {
// u2 start_pc;
out.writeShort(e.startPc);
// u2 end_pc;
out.writeShort(e.endPc);
// u2 handler_pc;
out.writeShort(e.handlerPc);
// u2 catch_type;
out.writeShort(e.catchType);
}
// u2 attributes_count;
out.writeShort(0);
// write "Exceptions" attribute. See JVMS section 4.7.4.
// u2 attribute_name_index;
out.writeShort(cp.getUtf8("Exceptions"));
// u4 attributes_length;
out.writeInt(2 + 2 * declaredExceptions.length);
// u2 number_of_exceptions;
out.writeShort(declaredExceptions.length);
// u2 exception_index_table[number_of_exceptions];
for (int i = 0; i < declaredExceptions.length; i++) {
out.writeShort(declaredExceptions[i]);
}
}
}
/**
* A ProxyMethod object represents a proxy method in the proxy class
* being generated: a method whose implementation will encode and
* dispatch invocations to the proxy instance's invocation handler.
*/
private class ProxyMethod {
public String methodName;
public Class[] parameterTypes;
public Class returnType;
public Class[] exceptionTypes;
public Class fromClass;
public String methodFieldName;
private ProxyMethod(String methodName, Class[] parameterTypes,
Class returnType, Class[] exceptionTypes,
Class fromClass)
{
this.methodName = methodName;
this.parameterTypes = parameterTypes;
this.returnType = returnType;
this.exceptionTypes = exceptionTypes;
this.fromClass = fromClass;
this.methodFieldName = "m" + proxyMethodCount++;
}
/**
* Return a MethodInfo object for this method, including generating
* the code and exception table entry.
*/
private MethodInfo generateMethod() throws IOException {
String desc = getMethodDescriptor(parameterTypes, returnType);
MethodInfo minfo = new MethodInfo(methodName, desc,
ACC_PUBLIC | ACC_FINAL);
int[] parameterSlot = new int[parameterTypes.length];
int nextSlot = 1;
for (int i = 0; i < parameterSlot.length; i++) {
parameterSlot[i] = nextSlot;
nextSlot += getWordsPerType(parameterTypes[i]);
}
int localSlot0 = nextSlot;
short pc, tryBegin = 0, tryEnd;
DataOutputStream out = new DataOutputStream(minfo.code);
code_aload(0, out);
out.writeByte(opc_getfield);
out.writeShort(cp.getFieldRef(
superclassName,
handlerFieldName, "Ljava/lang/reflect/InvocationHandler;"));
code_aload(0, out);
out.writeByte(opc_getstatic);
out.writeShort(cp.getFieldRef(
dotToSlash(className),
methodFieldName, "Ljava/lang/reflect/Method;"));
if (parameterTypes.length > 0) {
code_ipush(parameterTypes.length, out);
out.writeByte(opc_anewarray);
out.writeShort(cp.getClass("java/lang/Object"));
for (int i = 0; i < parameterTypes.length; i++) {
out.writeByte(opc_dup);
code_ipush(i, out);
codeWrapArgument(parameterTypes[i], parameterSlot[i], out);
out.writeByte(opc_aastore);
}
} else {
out.writeByte(opc_aconst_null);
}
out.writeByte(opc_invokeinterface);
out.writeShort(cp.getInterfaceMethodRef(
"java/lang/reflect/InvocationHandler",
"invoke",
"(Ljava/lang/Object;Ljava/lang/reflect/Method;" +
"[Ljava/lang/Object;)Ljava/lang/Object;"));
out.writeByte(4);
out.writeByte(0);
if (returnType == void.class) {
out.writeByte(opc_pop);
out.writeByte(opc_return);
} else {
codeUnwrapReturnValue(returnType, out);
}
tryEnd = pc = (short) minfo.code.size();
List<Class<?>> catchList = computeUniqueCatchList(exceptionTypes);
if (catchList.size() > 0) {
for (Class<?> ex : catchList) {
minfo.exceptionTable.add(new ExceptionTableEntry(
tryBegin, tryEnd, pc,
cp.getClass(dotToSlash(ex.getName()))));
}
out.writeByte(opc_athrow);
pc = (short) minfo.code.size();
minfo.exceptionTable.add(new ExceptionTableEntry(
tryBegin, tryEnd, pc, cp.getClass("java/lang/Throwable")));
code_astore(localSlot0, out);
out.writeByte(opc_new);
out.writeShort(cp.getClass(
"java/lang/reflect/UndeclaredThrowableException"));
out.writeByte(opc_dup);
code_aload(localSlot0, out);
out.writeByte(opc_invokespecial);
out.writeShort(cp.getMethodRef(
"java/lang/reflect/UndeclaredThrowableException",
"<init>", "(Ljava/lang/Throwable;)V"));
out.writeByte(opc_athrow);
}
if (minfo.code.size() > 65535) {
throw new IllegalArgumentException("code size limit exceeded");
}
minfo.maxStack = 10;
minfo.maxLocals = (short) (localSlot0 + 1);
minfo.declaredExceptions = new short[exceptionTypes.length];
for (int i = 0; i < exceptionTypes.length; i++) {
minfo.declaredExceptions[i] = cp.getClass(
dotToSlash(exceptionTypes[i].getName()));
}
return minfo;
}
/**
* Generate code for wrapping an argument of the given type
* whose value can be found at the specified local variable
* index, in order for it to be passed (as an Object) to the
* invocation handler's "invoke" method. The code is written
* to the supplied stream.
*/
private void codeWrapArgument(Class type, int slot,
DataOutputStream out)
throws IOException
{
if (type.isPrimitive()) {
PrimitiveTypeInfo prim = PrimitiveTypeInfo.get(type);
if (type == int.class ||
type == boolean.class ||
type == byte.class ||
type == char.class ||
type == short.class)
{
code_iload(slot, out);
} else if (type == long.class) {
code_lload(slot, out);
} else if (type == float.class) {
code_fload(slot, out);
} else if (type == double.class) {
code_dload(slot, out);
} else {
throw new AssertionError();
}
out.writeByte(opc_invokestatic);
out.writeShort(cp.getMethodRef(
prim.wrapperClassName,
"valueOf", prim.wrapperValueOfDesc));
} else {
code_aload(slot, out);
}
}
/**
* Generate code for unwrapping a return value of the given
* type from the invocation handler's "invoke" method (as type
* Object) to its correct type. The code is written to the
* supplied stream.
*/
private void codeUnwrapReturnValue(Class type, DataOutputStream out)
throws IOException
{
if (type.isPrimitive()) {
PrimitiveTypeInfo prim = PrimitiveTypeInfo.get(type);
out.writeByte(opc_checkcast);
out.writeShort(cp.getClass(prim.wrapperClassName));
out.writeByte(opc_invokevirtual);
out.writeShort(cp.getMethodRef(
prim.wrapperClassName,
prim.unwrapMethodName, prim.unwrapMethodDesc));
if (type == int.class ||
type == boolean.class ||
type == byte.class ||
type == char.class ||
type == short.class)
{
out.writeByte(opc_ireturn);
} else if (type == long.class) {
out.writeByte(opc_lreturn);
} else if (type == float.class) {
out.writeByte(opc_freturn);
} else if (type == double.class) {
out.writeByte(opc_dreturn);
} else {
throw new AssertionError();
}
} else {
out.writeByte(opc_checkcast);
out.writeShort(cp.getClass(dotToSlash(type.getName())));
out.writeByte(opc_areturn);
}
}
/**
* Generate code for initializing the static field that stores
* the Method object for this proxy method. The code is written
* to the supplied stream.
*/
private void codeFieldInitialization(DataOutputStream out)
throws IOException
{
codeClassForName(fromClass, out);
code_ldc(cp.getString(methodName), out);
code_ipush(parameterTypes.length, out);
out.writeByte(opc_anewarray);
out.writeShort(cp.getClass("java/lang/Class"));
for (int i = 0; i < parameterTypes.length; i++) {
out.writeByte(opc_dup);
code_ipush(i, out);
if (parameterTypes[i].isPrimitive()) {
PrimitiveTypeInfo prim =
PrimitiveTypeInfo.get(parameterTypes[i]);
out.writeByte(opc_getstatic);
out.writeShort(cp.getFieldRef(
prim.wrapperClassName, "TYPE", "Ljava/lang/Class;"));
} else {
codeClassForName(parameterTypes[i], out);
}
out.writeByte(opc_aastore);
}
out.writeByte(opc_invokevirtual);
out.writeShort(cp.getMethodRef(
"java/lang/Class",
"getMethod",
"(Ljava/lang/String;[Ljava/lang/Class;)" +
"Ljava/lang/reflect/Method;"));
out.writeByte(opc_putstatic);
out.writeShort(cp.getFieldRef(
dotToSlash(className),
methodFieldName, "Ljava/lang/reflect/Method;"));
}
}
/**
* Generate the constructor method for the proxy class.
*/
private MethodInfo generateConstructor() throws IOException {
MethodInfo minfo = new MethodInfo(
"<init>", "(Ljava/lang/reflect/InvocationHandler;)V",
ACC_PUBLIC);
DataOutputStream out = new DataOutputStream(minfo.code);
code_aload(0, out);
code_aload(1, out);
out.writeByte(opc_invokespecial);
out.writeShort(cp.getMethodRef(
superclassName,
"<init>", "(Ljava/lang/reflect/InvocationHandler;)V"));
out.writeByte(opc_return);
minfo.maxStack = 10;
minfo.maxLocals = 2;
minfo.declaredExceptions = new short[0];
return minfo;
}
/**
* Generate the static initializer method for the proxy class.
*/
private MethodInfo generateStaticInitializer() throws IOException {
MethodInfo minfo = new MethodInfo(
"<clinit>", "()V", ACC_STATIC);
int localSlot0 = 1;
short pc, tryBegin = 0, tryEnd;
DataOutputStream out = new DataOutputStream(minfo.code);
for (List<ProxyMethod> sigmethods : proxyMethods.values()) {
for (ProxyMethod pm : sigmethods) {
pm.codeFieldInitialization(out);
}
}
out.writeByte(opc_return);
tryEnd = pc = (short) minfo.code.size();
minfo.exceptionTable.add(new ExceptionTableEntry(
tryBegin, tryEnd, pc,
cp.getClass("java/lang/NoSuchMethodException")));
code_astore(localSlot0, out);
out.writeByte(opc_new);
out.writeShort(cp.getClass("java/lang/NoSuchMethodError"));
out.writeByte(opc_dup);
code_aload(localSlot0, out);
out.writeByte(opc_invokevirtual);
out.writeShort(cp.getMethodRef(
"java/lang/Throwable", "getMessage", "()Ljava/lang/String;"));
out.writeByte(opc_invokespecial);
out.writeShort(cp.getMethodRef(
"java/lang/NoSuchMethodError", "<init>", "(Ljava/lang/String;)V"));
out.writeByte(opc_athrow);
pc = (short) minfo.code.size();
minfo.exceptionTable.add(new ExceptionTableEntry(
tryBegin, tryEnd, pc,
cp.getClass("java/lang/ClassNotFoundException")));
code_astore(localSlot0, out);
out.writeByte(opc_new);
out.writeShort(cp.getClass("java/lang/NoClassDefFoundError"));
out.writeByte(opc_dup);
code_aload(localSlot0, out);
out.writeByte(opc_invokevirtual);
out.writeShort(cp.getMethodRef(
"java/lang/Throwable", "getMessage", "()Ljava/lang/String;"));
out.writeByte(opc_invokespecial);
out.writeShort(cp.getMethodRef(
"java/lang/NoClassDefFoundError",
"<init>", "(Ljava/lang/String;)V"));
out.writeByte(opc_athrow);
if (minfo.code.size() > 65535) {
throw new IllegalArgumentException("code size limit exceeded");
}
minfo.maxStack = 10;
minfo.maxLocals = (short) (localSlot0 + 1);
minfo.declaredExceptions = new short[0];
return minfo;
}
/*
* =============== Code Generation Utility Methods ===============
*/
/*
* The following methods generate code for the load or store operation
* indicated by their name for the given local variable. The code is
* written to the supplied stream.
*/
private void code_iload(int lvar, DataOutputStream out)
throws IOException
{
codeLocalLoadStore(lvar, opc_iload, opc_iload_0, out);
}
private void code_lload(int lvar, DataOutputStream out)
throws IOException
{
codeLocalLoadStore(lvar, opc_lload, opc_lload_0, out);
}
private void code_fload(int lvar, DataOutputStream out)
throws IOException
{
codeLocalLoadStore(lvar, opc_fload, opc_fload_0, out);
}
private void code_dload(int lvar, DataOutputStream out)
throws IOException
{
codeLocalLoadStore(lvar, opc_dload, opc_dload_0, out);
}
private void code_aload(int lvar, DataOutputStream out)
throws IOException
{
codeLocalLoadStore(lvar, opc_aload, opc_aload_0, out);
}
// private void code_istore(int lvar, DataOutputStream out)
// throws IOException
// {
// codeLocalLoadStore(lvar, opc_istore, opc_istore_0, out);
// }
// private void code_lstore(int lvar, DataOutputStream out)
// throws IOException
// {
// codeLocalLoadStore(lvar, opc_lstore, opc_lstore_0, out);
// }
// private void code_fstore(int lvar, DataOutputStream out)
// throws IOException
// {
// codeLocalLoadStore(lvar, opc_fstore, opc_fstore_0, out);
// }
// private void code_dstore(int lvar, DataOutputStream out)
// throws IOException
// {
// codeLocalLoadStore(lvar, opc_dstore, opc_dstore_0, out);
// }
private void code_astore(int lvar, DataOutputStream out)
throws IOException
{
codeLocalLoadStore(lvar, opc_astore, opc_astore_0, out);
}
/**
* Generate code for a load or store instruction for the given local
* variable. The code is written to the supplied stream.
*
* "opcode" indicates the opcode form of the desired load or store
* instruction that takes an explicit local variable index, and
* "opcode_0" indicates the corresponding form of the instruction
* with the implicit index 0.
*/
private void codeLocalLoadStore(int lvar, int opcode, int opcode_0,
DataOutputStream out)
throws IOException
{
assert lvar >= 0 && lvar <= 0xFFFF;
if (lvar <= 3) {
out.writeByte(opcode_0 + lvar);
} else if (lvar <= 0xFF) {
out.writeByte(opcode);
out.writeByte(lvar & 0xFF);
} else {
/*
* Use the "wide" instruction modifier for local variable
* indexes that do not fit into an unsigned byte.
*/
out.writeByte(opc_wide);
out.writeByte(opcode);
out.writeShort(lvar & 0xFFFF);
}
}
/**
* Generate code for an "ldc" instruction for the given constant pool
* index (the "ldc_w" instruction is used if the index does not fit
* into an unsigned byte). The code is written to the supplied stream.
*/
private void code_ldc(int index, DataOutputStream out)
throws IOException
{
assert index >= 0 && index <= 0xFFFF;
if (index <= 0xFF) {
out.writeByte(opc_ldc);
out.writeByte(index & 0xFF);
} else {
out.writeByte(opc_ldc_w);
out.writeShort(index & 0xFFFF);
}
}
/**
* Generate code to push a constant integer value on to the operand
* stack, using the "iconst_<i>", "bipush", or "sipush" instructions
* depending on the size of the value. The code is written to the
* supplied stream.
*/
private void code_ipush(int value, DataOutputStream out)
throws IOException
{
if (value >= -1 && value <= 5) {
out.writeByte(opc_iconst_0 + value);
} else if (value >= Byte.MIN_VALUE && value <= Byte.MAX_VALUE) {
out.writeByte(opc_bipush);
out.writeByte(value & 0xFF);
} else if (value >= Short.MIN_VALUE && value <= Short.MAX_VALUE) {
out.writeByte(opc_sipush);
out.writeShort(value & 0xFFFF);
} else {
throw new AssertionError();
}
}
/**
* Generate code to invoke the Class.forName with the name of the given
* class to get its Class object at runtime. The code is written to
* the supplied stream. Note that the code generated by this method
* may caused the checked ClassNotFoundException to be thrown.
*/
private void codeClassForName(Class cl, DataOutputStream out)
throws IOException
{
code_ldc(cp.getString(cl.getName()), out);
out.writeByte(opc_invokestatic);
out.writeShort(cp.getMethodRef(
"java/lang/Class",
"forName", "(Ljava/lang/String;)Ljava/lang/Class;"));
}
/*
* ==================== General Utility Methods ====================
*/
/**
* Convert a fully qualified class name that uses '.' as the package
* separator, the external representation used by the Java language
* and APIs, to a fully qualified class name that uses '/' as the
* package separator, the representation used in the class file
* format (see JVMS section 4.2).
*/
private static String dotToSlash(String name) {
return name.replace('.', '/');
}
/**
* Return the "method descriptor" string for a method with the given
* parameter types and return type. See JVMS section 4.3.3.
*/
private static String getMethodDescriptor(Class[] parameterTypes,
Class returnType)
{
return getParameterDescriptors(parameterTypes) +
((returnType == void.class) ? "V" : getFieldType(returnType));
}
/**
* Return the list of "parameter descriptor" strings enclosed in
* parentheses corresponding to the given parameter types (in other
* words, a method descriptor without a return descriptor). This
* string is useful for constructing string keys for methods without
* regard to their return type.
*/
private static String getParameterDescriptors(Class[] parameterTypes) {
StringBuilder desc = new StringBuilder("(");
for (int i = 0; i < parameterTypes.length; i++) {
desc.append(getFieldType(parameterTypes[i]));
}
desc.append(')');
return desc.toString();
}
/**
* Return the "field type" string for the given type, appropriate for
* a field descriptor, a parameter descriptor, or a return descriptor
* other than "void". See JVMS section 4.3.2.
*/
private static String getFieldType(Class type) {
if (type.isPrimitive()) {
return PrimitiveTypeInfo.get(type).baseTypeString;
} else if (type.isArray()) {
/*
* According to JLS 20.3.2, the getName() method on Class does
* return the VM type descriptor format for array classes (only);
* using that should be quicker than the otherwise obvious code:
*
* return "[" + getTypeDescriptor(type.getComponentType());
*/
return type.getName().replace('.', '/');
} else {
return "L" + dotToSlash(type.getName()) + ";";
}
}
/**
* Returns a human-readable string representing the signature of a
* method with the given name and parameter types.
*/
private static String getFriendlyMethodSignature(String name,
Class[] parameterTypes)
{
StringBuilder sig = new StringBuilder(name);
sig.append('(');
for (int i = 0; i < parameterTypes.length; i++) {
if (i > 0) {
sig.append(',');
}
Class parameterType = parameterTypes[i];
int dimensions = 0;
while (parameterType.isArray()) {
parameterType = parameterType.getComponentType();
dimensions++;
}
sig.append(parameterType.getName());
while (dimensions-- > 0) {
sig.append("[]");
}
}
sig.append(')');
return sig.toString();
}
/**
* Return the number of abstract "words", or consecutive local variable
* indexes, required to contain a value of the given type. See JVMS
* section 3.6.1.
*
* Note that the original version of the JVMS contained a definition of
* this abstract notion of a "word" in section 3.4, but that definition
* was removed for the second edition.
*/
private static int getWordsPerType(Class type) {
if (type == long.class || type == double.class) {
return 2;
} else {
return 1;
}
}
/**
* Add to the given list all of the types in the "from" array that
* are not already contained in the list and are assignable to at
* least one of the types in the "with" array.
*
* This method is useful for computing the greatest common set of
* declared exceptions from duplicate methods inherited from
* different interfaces.
*/
private static void collectCompatibleTypes(Class<?>[] from,
Class<?>[] with,
List<Class<?>> list)
{
for (int i = 0; i < from.length; i++) {
if (!list.contains(from[i])) {
for (int j = 0; j < with.length; j++) {
if (with[j].isAssignableFrom(from[i])) {
list.add(from[i]);
break;
}
}
}
}
}
/**
* Given the exceptions declared in the throws clause of a proxy method,
* compute the exceptions that need to be caught from the invocation
* handler's invoke method and rethrown intact in the method's
* implementation before catching other Throwables and wrapping them
* in UndeclaredThrowableExceptions.
*
* The exceptions to be caught are returned in a List object. Each
* exception in the returned list is guaranteed to not be a subclass of
* any of the other exceptions in the list, so the catch blocks for
* these exceptions may be generated in any order relative to each other.
*
* Error and RuntimeException are each always contained by the returned
* list (if none of their superclasses are contained), since those
* unchecked exceptions should always be rethrown intact, and thus their
* subclasses will never appear in the returned list.
*
* The returned List will be empty if java.lang.Throwable is in the
* given list of declared exceptions, indicating that no exceptions
* need to be caught.
*/
private static List<Class<?>> computeUniqueCatchList(Class<?>[] exceptions) {
List<Class<?>> uniqueList = new ArrayList<Class<?>>();
// unique exceptions to catch
uniqueList.add(Error.class); // always catch/rethrow these
uniqueList.add(RuntimeException.class);
nextException:
for (int i = 0; i < exceptions.length; i++) {
Class<?> ex = exceptions[i];
if (ex.isAssignableFrom(Throwable.class)) {
/*
* If Throwable is declared to be thrown by the proxy method,
* then no catch blocks are necessary, because the invoke
* can, at most, throw Throwable anyway.
*/
uniqueList.clear();
break;
} else if (!Throwable.class.isAssignableFrom(ex)) {
/*
* Ignore types that cannot be thrown by the invoke method.
*/
continue;
}
/*
* Compare this exception against the current list of
* exceptions that need to be caught:
*/
for (int j = 0; j < uniqueList.size();) {
Class<?> ex2 = uniqueList.get(j);
if (ex2.isAssignableFrom(ex)) {
/*
* if a superclass of this exception is already on
* the list to catch, then ignore this one and continue;
*/
continue nextException;
} else if (ex.isAssignableFrom(ex2)) {
/*
* if a subclass of this exception is on the list
* to catch, then remove it;
*/
uniqueList.remove(j);
} else {
j++; // else continue comparing.
}
}
// This exception is unique (so far): add it to the list to catch.
uniqueList.add(ex);
}
return uniqueList;
}
/**
* A PrimitiveTypeInfo object contains assorted information about
* a primitive type in its public fields. The struct for a particular
* primitive type can be obtained using the static "get" method.
*/
private static class PrimitiveTypeInfo {
/** "base type" used in various descriptors (see JVMS section 4.3.2) */
public String baseTypeString;
/** name of corresponding wrapper class */
public String wrapperClassName;
/** method descriptor for wrapper class "valueOf" factory method */
public String wrapperValueOfDesc;
/** name of wrapper class method for retrieving primitive value */
public String unwrapMethodName;
/** descriptor of same method */
public String unwrapMethodDesc;
private static Map<Class,PrimitiveTypeInfo> table =
new HashMap<Class,PrimitiveTypeInfo>();
static {
add(byte.class, Byte.class);
add(char.class, Character.class);
add(double.class, Double.class);
add(float.class, Float.class);
add(int.class, Integer.class);
add(long.class, Long.class);
add(short.class, Short.class);
add(boolean.class, Boolean.class);
}
private static void add(Class primitiveClass, Class wrapperClass) {
table.put(primitiveClass,
new PrimitiveTypeInfo(primitiveClass, wrapperClass));
}
private PrimitiveTypeInfo(Class primitiveClass, Class wrapperClass) {
assert primitiveClass.isPrimitive();
baseTypeString =
Array.newInstance(primitiveClass, 0)
.getClass().getName().substring(1);
wrapperClassName = dotToSlash(wrapperClass.getName());
wrapperValueOfDesc =
"(" + baseTypeString + ")L" + wrapperClassName + ";";
unwrapMethodName = primitiveClass.getName() + "Value";
unwrapMethodDesc = "()" + baseTypeString;
}
public static PrimitiveTypeInfo get(Class cl) {
return table.get(cl);
}
}
/**
* A ConstantPool object represents the constant pool of a class file
* being generated. This representation of a constant pool is designed
* specifically for use by ProxyGenerator; in particular, it assumes
* that constant pool entries will not need to be resorted (for example,
* by their type, as the Java compiler does), so that the final index
* value can be assigned and used when an entry is first created.
*
* Note that new entries cannot be created after the constant pool has
* been written to a class file. To prevent such logic errors, a
* ConstantPool instance can be marked "read only", so that further
* attempts to add new entries will fail with a runtime exception.
*
* See JVMS section 4.4 for more information about the constant pool
* of a class file.
*/
private static class ConstantPool {
/**
* list of constant pool entries, in constant pool index order.
*
* This list is used when writing the constant pool to a stream
* and for assigning the next index value. Note that element 0
* of this list corresponds to constant pool index 1.
*/
private List<Entry> pool = new ArrayList<Entry>(32);
/**
* maps constant pool data of all types to constant pool indexes.
*
* This map is used to look up the index of an existing entry for
* values of all types.
*/
private Map<Object,Short> map = new HashMap<Object,Short>(16);
/** true if no new constant pool entries may be added */
private boolean readOnly = false;
/**
* Get or assign the index for a CONSTANT_Utf8 entry.
*/
public short getUtf8(String s) {
if (s == null) {
throw new NullPointerException();
}
return getValue(s);
}
/**
* Get or assign the index for a CONSTANT_Integer entry.
*/
public short getInteger(int i) {
return getValue(new Integer(i));
}
/**
* Get or assign the index for a CONSTANT_Float entry.
*/
public short getFloat(float f) {
return getValue(new Float(f));
}
/**
* Get or assign the index for a CONSTANT_Class entry.
*/
public short getClass(String name) {
short utf8Index = getUtf8(name);
return getIndirect(new IndirectEntry(
CONSTANT_CLASS, utf8Index));
}
/**
* Get or assign the index for a CONSTANT_String entry.
*/
public short getString(String s) {
short utf8Index = getUtf8(s);
return getIndirect(new IndirectEntry(
CONSTANT_STRING, utf8Index));
}
/**
* Get or assign the index for a CONSTANT_FieldRef entry.
*/
public short getFieldRef(String className,
String name, String descriptor)
{
short classIndex = getClass(className);
short nameAndTypeIndex = getNameAndType(name, descriptor);
return getIndirect(new IndirectEntry(
CONSTANT_FIELD, classIndex, nameAndTypeIndex));
}
/**
* Get or assign the index for a CONSTANT_MethodRef entry.
*/
public short getMethodRef(String className,
String name, String descriptor)
{
short classIndex = getClass(className);
short nameAndTypeIndex = getNameAndType(name, descriptor);
return getIndirect(new IndirectEntry(
CONSTANT_METHOD, classIndex, nameAndTypeIndex));
}
/**
* Get or assign the index for a CONSTANT_InterfaceMethodRef entry.
*/
public short getInterfaceMethodRef(String className, String name,
String descriptor)
{
short classIndex = getClass(className);
short nameAndTypeIndex = getNameAndType(name, descriptor);
return getIndirect(new IndirectEntry(
CONSTANT_INTERFACEMETHOD, classIndex, nameAndTypeIndex));
}
/**
* Get or assign the index for a CONSTANT_NameAndType entry.
*/
public short getNameAndType(String name, String descriptor) {
short nameIndex = getUtf8(name);
short descriptorIndex = getUtf8(descriptor);
return getIndirect(new IndirectEntry(
CONSTANT_NAMEANDTYPE, nameIndex, descriptorIndex));
}
/**
* Set this ConstantPool instance to be "read only".
*
* After this method has been called, further requests to get
* an index for a non-existent entry will cause an InternalError
* to be thrown instead of creating of the entry.
*/
public void setReadOnly() {
readOnly = true;
}
/**
* Write this constant pool to a stream as part of
* the class file format.
*
* This consists of writing the "constant_pool_count" and
* "constant_pool[]" items of the "ClassFile" structure, as
* described in JVMS section 4.1.
*/
public void write(OutputStream out) throws IOException {
DataOutputStream dataOut = new DataOutputStream(out);
// constant_pool_count: number of entries plus one
dataOut.writeShort(pool.size() + 1);
for (Entry e : pool) {
e.write(dataOut);
}
}
/**
* Add a new constant pool entry and return its index.
*/
private short addEntry(Entry entry) {
pool.add(entry);
/*
* Note that this way of determining the index of the
* added entry is wrong if this pool supports
* CONSTANT_Long or CONSTANT_Double entries.
*/
if (pool.size() >= 65535) {
throw new IllegalArgumentException(
"constant pool size limit exceeded");
}
return (short) pool.size();
}
/**
* Get or assign the index for an entry of a type that contains
* a direct value. The type of the given object determines the
* type of the desired entry as follows:
*
* java.lang.String CONSTANT_Utf8
* java.lang.Integer CONSTANT_Integer
* java.lang.Float CONSTANT_Float
* java.lang.Long CONSTANT_Long
* java.lang.Double CONSTANT_DOUBLE
*/
private short getValue(Object key) {
Short index = map.get(key);
if (index != null) {
return index.shortValue();
} else {
if (readOnly) {
throw new InternalError(
"late constant pool addition: " + key);
}
short i = addEntry(new ValueEntry(key));
map.put(key, new Short(i));
return i;
}
}
/**
* Get or assign the index for an entry of a type that contains
* references to other constant pool entries.
*/
private short getIndirect(IndirectEntry e) {
Short index = map.get(e);
if (index != null) {
return index.shortValue();
} else {
if (readOnly) {
throw new InternalError("late constant pool addition");
}
short i = addEntry(e);
map.put(e, new Short(i));
return i;
}
}
/**
* Entry is the abstact superclass of all constant pool entry types
* that can be stored in the "pool" list; its purpose is to define a
* common method for writing constant pool entries to a class file.
*/
private static abstract class Entry {
public abstract void write(DataOutputStream out)
throws IOException;
}
/**
* ValueEntry represents a constant pool entry of a type that
* contains a direct value (see the comments for the "getValue"
* method for a list of such types).
*
* ValueEntry objects are not used as keys for their entries in the
* Map "map", so no useful hashCode or equals methods are defined.
*/
private static class ValueEntry extends Entry {
private Object value;
public ValueEntry(Object value) {
this.value = value;
}
public void write(DataOutputStream out) throws IOException {
if (value instanceof String) {
out.writeByte(CONSTANT_UTF8);
out.writeUTF((String) value);
} else if (value instanceof Integer) {
out.writeByte(CONSTANT_INTEGER);
out.writeInt(((Integer) value).intValue());
} else if (value instanceof Float) {
out.writeByte(CONSTANT_FLOAT);
out.writeFloat(((Float) value).floatValue());
} else if (value instanceof Long) {
out.writeByte(CONSTANT_LONG);
out.writeLong(((Long) value).longValue());
} else if (value instanceof Double) {
out.writeDouble(CONSTANT_DOUBLE);
out.writeDouble(((Double) value).doubleValue());
} else {
throw new InternalError("bogus value entry: " + value);
}
}
}
/**
* IndirectEntry represents a constant pool entry of a type that
* references other constant pool entries, i.e., the following types:
*
* CONSTANT_Class, CONSTANT_String, CONSTANT_Fieldref,
* CONSTANT_Methodref, CONSTANT_InterfaceMethodref, and
* CONSTANT_NameAndType.
*
* Each of these entry types contains either one or two indexes of
* other constant pool entries.
*
* IndirectEntry objects are used as the keys for their entries in
* the Map "map", so the hashCode and equals methods are overridden
* to allow matching.
*/
private static class IndirectEntry extends Entry {
private int tag;
private short index0;
private short index1;
/**
* Construct an IndirectEntry for a constant pool entry type
* that contains one index of another entry.
*/
public IndirectEntry(int tag, short index) {
this.tag = tag;
this.index0 = index;
this.index1 = 0;
}
/**
* Construct an IndirectEntry for a constant pool entry type
* that contains two indexes for other entries.
*/
public IndirectEntry(int tag, short index0, short index1) {
this.tag = tag;
this.index0 = index0;
this.index1 = index1;
}
public void write(DataOutputStream out) throws IOException {
out.writeByte(tag);
out.writeShort(index0);
/*
* If this entry type contains two indexes, write
* out the second, too.
*/
if (tag == CONSTANT_FIELD ||
tag == CONSTANT_METHOD ||
tag == CONSTANT_INTERFACEMETHOD ||
tag == CONSTANT_NAMEANDTYPE)
{
out.writeShort(index1);
}
}
public int hashCode() {
return tag + index0 + index1;
}
public boolean equals(Object obj) {
if (obj instanceof IndirectEntry) {
IndirectEntry other = (IndirectEntry) obj;
if (tag == other.tag &&
index0 == other.index0 && index1 == other.index1)
{
return true;
}
}
return false;
}
}
}
}
To have an intuitive understanding of the generated class file, we turn on the option of saveGeneratedFiles.
// Target.java
package dynamicproxy;
public interface Target {
void foo();
}
// TargetProxyInvocationHandler.java
package dynamicproxy;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
public class TargetProxyInvocationHandler implements InvocationHandler {
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
if("foo".equals(method.getName())) {
System.out.println("foo invoked");
}
return null;
}
}
// Main.java
package dynamicproxy;
import java.lang.reflect.Proxy;
public class Main {
public static void main(String[] args) {
System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles","true");
Target b = (Target) Proxy.newProxyInstance(Target.class.getClassLoader(), new Class[] {Target.class}, new TargetProxyInvocationHandler());
System.out.println(b.getClass().toString());
b.foo();
}
}
And now we can find the generated Proxy class file:
// Proxy.class
package com.sun.proxy;
import dynamicproxy.Target;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.UndeclaredThrowableException;
public final class $Proxy0 extends Proxy implements Target {
private static Method m0;
private static Method m1;
private static Method m2;
private static Method m3;
static {
try {
m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);
m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[]{Class.forName("java.lang.Object")});
m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);
m3 = Class.forName("dynamicproxy.Target").getMethod("foo", new Class[0]);
} catch (NoSuchMethodException var2) {
throw new NoSuchMethodError(var2.getMessage());
} catch (ClassNotFoundException var3) {
throw new NoClassDefFoundError(var3.getMessage());
}
}
public $Proxy0(InvocationHandler var1) throws {
super(var1);
}
public final int hashCode() throws {
try {
return ((Integer)super.h.invoke(this, m0, (Object[])null)).intValue();
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
public final boolean equals(Object var1) throws {
try {
return ((Boolean)super.h.invoke(this, m1, new Object[]{var1})).booleanValue();
} catch (RuntimeException | Error var3) {
throw var3;
} catch (Throwable var4) {
throw new UndeclaredThrowableException(var4);
}
}
public final String toString() throws {
try {
return (String)super.h.invoke(this, m2, (Object[])null);
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
public final void foo() throws {
try {
super.h.invoke(this, m3, (Object[])null);
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
}
Implement Dynamic Proxy supporting Class
A restriction of the Proxy provided by JDK is that we can only get a proxy for an interface rather than a class.
But can we implement this feature on our own?
Obviously, we need to modify ProxyGenerator to control the generation of the final class as our expectation.
package dynamicproxy.supportclass;
import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.lang.reflect.Array;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;
import sun.security.action.GetBooleanAction;
/**
* ProxyGeneratorEx contains the code to generate a dynamic proxy class
* for any class.
*/
public class ProxyGeneratorEx {
/*
* In the comments below, "JVMS" refers to The Java Virtual Machine
* Specification Second Edition and "JLS" refers to the original
* version of The Java Language Specification, unless otherwise
* specified.
*/
/* generate 1.5-era class file version */
private static final int CLASSFILE_MAJOR_VERSION = 49;
private static final int CLASSFILE_MINOR_VERSION = 0;
/*
* beginning of constants copied from
* sun.tools.java.RuntimeConstants (which no longer exists):
*/
/* constant pool tags */
private static final int CONSTANT_UTF8 = 1;
private static final int CONSTANT_UNICODE = 2;
private static final int CONSTANT_INTEGER = 3;
private static final int CONSTANT_FLOAT = 4;
private static final int CONSTANT_LONG = 5;
private static final int CONSTANT_DOUBLE = 6;
private static final int CONSTANT_CLASS = 7;
private static final int CONSTANT_STRING = 8;
private static final int CONSTANT_FIELD = 9;
private static final int CONSTANT_METHOD = 10;
private static final int CONSTANT_INTERFACEMETHOD = 11;
private static final int CONSTANT_NAMEANDTYPE = 12;
/* access and modifier flags */
private static final int ACC_PUBLIC = 0x00000001;
private static final int ACC_PRIVATE = 0x00000002;
// private static final int ACC_PROTECTED = 0x00000004;
private static final int ACC_STATIC = 0x00000008;
private static final int ACC_FINAL = 0x00000010;
// private static final int ACC_SYNCHRONIZED = 0x00000020;
// private static final int ACC_VOLATILE = 0x00000040;
// private static final int ACC_TRANSIENT = 0x00000080;
// private static final int ACC_NATIVE = 0x00000100;
// private static final int ACC_INTERFACE = 0x00000200;
// private static final int ACC_ABSTRACT = 0x00000400;
private static final int ACC_SUPER = 0x00000020;
// private static final int ACC_STRICT = 0x00000800;
/* opcodes */
// private static final int opc_nop = 0;
private static final int opc_aconst_null = 1;
// private static final int opc_iconst_m1 = 2;
private static final int opc_iconst_0 = 3;
// private static final int opc_iconst_1 = 4;
// private static final int opc_iconst_2 = 5;
// private static final int opc_iconst_3 = 6;
// private static final int opc_iconst_4 = 7;
// private static final int opc_iconst_5 = 8;
// private static final int opc_lconst_0 = 9;
// private static final int opc_lconst_1 = 10;
// private static final int opc_fconst_0 = 11;
// private static final int opc_fconst_1 = 12;
// private static final int opc_fconst_2 = 13;
// private static final int opc_dconst_0 = 14;
// private static final int opc_dconst_1 = 15;
private static final int opc_bipush = 16;
private static final int opc_sipush = 17;
private static final int opc_ldc = 18;
private static final int opc_ldc_w = 19;
// private static final int opc_ldc2_w = 20;
private static final int opc_iload = 21;
private static final int opc_lload = 22;
private static final int opc_fload = 23;
private static final int opc_dload = 24;
private static final int opc_aload = 25;
private static final int opc_iload_0 = 26;
// private static final int opc_iload_1 = 27;
// private static final int opc_iload_2 = 28;
// private static final int opc_iload_3 = 29;
private static final int opc_lload_0 = 30;
// private static final int opc_lload_1 = 31;
// private static final int opc_lload_2 = 32;
// private static final int opc_lload_3 = 33;
private static final int opc_fload_0 = 34;
// private static final int opc_fload_1 = 35;
// private static final int opc_fload_2 = 36;
// private static final int opc_fload_3 = 37;
private static final int opc_dload_0 = 38;
// private static final int opc_dload_1 = 39;
// private static final int opc_dload_2 = 40;
// private static final int opc_dload_3 = 41;
private static final int opc_aload_0 = 42;
// private static final int opc_aload_1 = 43;
// private static final int opc_aload_2 = 44;
// private static final int opc_aload_3 = 45;
// private static final int opc_iaload = 46;
// private static final int opc_laload = 47;
// private static final int opc_faload = 48;
// private static final int opc_daload = 49;
// private static final int opc_aaload = 50;
// private static final int opc_baload = 51;
// private static final int opc_caload = 52;
// private static final int opc_saload = 53;
// private static final int opc_istore = 54;
// private static final int opc_lstore = 55;
// private static final int opc_fstore = 56;
// private static final int opc_dstore = 57;
private static final int opc_astore = 58;
// private static final int opc_istore_0 = 59;
// private static final int opc_istore_1 = 60;
// private static final int opc_istore_2 = 61;
// private static final int opc_istore_3 = 62;
// private static final int opc_lstore_0 = 63;
// private static final int opc_lstore_1 = 64;
// private static final int opc_lstore_2 = 65;
// private static final int opc_lstore_3 = 66;
// private static final int opc_fstore_0 = 67;
// private static final int opc_fstore_1 = 68;
// private static final int opc_fstore_2 = 69;
// private static final int opc_fstore_3 = 70;
// private static final int opc_dstore_0 = 71;
// private static final int opc_dstore_1 = 72;
// private static final int opc_dstore_2 = 73;
// private static final int opc_dstore_3 = 74;
private static final int opc_astore_0 = 75;
// private static final int opc_astore_1 = 76;
// private static final int opc_astore_2 = 77;
// private static final int opc_astore_3 = 78;
// private static final int opc_iastore = 79;
// private static final int opc_lastore = 80;
// private static final int opc_fastore = 81;
// private static final int opc_dastore = 82;
private static final int opc_aastore = 83;
// private static final int opc_bastore = 84;
// private static final int opc_castore = 85;
// private static final int opc_sastore = 86;
private static final int opc_pop = 87;
// private static final int opc_pop2 = 88;
private static final int opc_dup = 89;
// private static final int opc_dup_x1 = 90;
// private static final int opc_dup_x2 = 91;
// private static final int opc_dup2 = 92;
// private static final int opc_dup2_x1 = 93;
// private static final int opc_dup2_x2 = 94;
// private static final int opc_swap = 95;
// private static final int opc_iadd = 96;
// private static final int opc_ladd = 97;
// private static final int opc_fadd = 98;
// private static final int opc_dadd = 99;
// private static final int opc_isub = 100;
// private static final int opc_lsub = 101;
// private static final int opc_fsub = 102;
// private static final int opc_dsub = 103;
// private static final int opc_imul = 104;
// private static final int opc_lmul = 105;
// private static final int opc_fmul = 106;
// private static final int opc_dmul = 107;
// private static final int opc_idiv = 108;
// private static final int opc_ldiv = 109;
// private static final int opc_fdiv = 110;
// private static final int opc_ddiv = 111;
// private static final int opc_irem = 112;
// private static final int opc_lrem = 113;
// private static final int opc_frem = 114;
// private static final int opc_drem = 115;
// private static final int opc_ineg = 116;
// private static final int opc_lneg = 117;
// private static final int opc_fneg = 118;
// private static final int opc_dneg = 119;
// private static final int opc_ishl = 120;
// private static final int opc_lshl = 121;
// private static final int opc_ishr = 122;
// private static final int opc_lshr = 123;
// private static final int opc_iushr = 124;
// private static final int opc_lushr = 125;
// private static final int opc_iand = 126;
// private static final int opc_land = 127;
// private static final int opc_ior = 128;
// private static final int opc_lor = 129;
// private static final int opc_ixor = 130;
// private static final int opc_lxor = 131;
// private static final int opc_iinc = 132;
// private static final int opc_i2l = 133;
// private static final int opc_i2f = 134;
// private static final int opc_i2d = 135;
// private static final int opc_l2i = 136;
// private static final int opc_l2f = 137;
// private static final int opc_l2d = 138;
// private static final int opc_f2i = 139;
// private static final int opc_f2l = 140;
// private static final int opc_f2d = 141;
// private static final int opc_d2i = 142;
// private static final int opc_d2l = 143;
// private static final int opc_d2f = 144;
// private static final int opc_i2b = 145;
// private static final int opc_i2c = 146;
// private static final int opc_i2s = 147;
// private static final int opc_lcmp = 148;
// private static final int opc_fcmpl = 149;
// private static final int opc_fcmpg = 150;
// private static final int opc_dcmpl = 151;
// private static final int opc_dcmpg = 152;
// private static final int opc_ifeq = 153;
// private static final int opc_ifne = 154;
// private static final int opc_iflt = 155;
// private static final int opc_ifge = 156;
// private static final int opc_ifgt = 157;
// private static final int opc_ifle = 158;
// private static final int opc_if_icmpeq = 159;
// private static final int opc_if_icmpne = 160;
// private static final int opc_if_icmplt = 161;
// private static final int opc_if_icmpge = 162;
// private static final int opc_if_icmpgt = 163;
// private static final int opc_if_icmple = 164;
// private static final int opc_if_acmpeq = 165;
// private static final int opc_if_acmpne = 166;
// private static final int opc_goto = 167;
// private static final int opc_jsr = 168;
// private static final int opc_ret = 169;
// private static final int opc_tableswitch = 170;
// private static final int opc_lookupswitch = 171;
private static final int opc_ireturn = 172;
private static final int opc_lreturn = 173;
private static final int opc_freturn = 174;
private static final int opc_dreturn = 175;
private static final int opc_areturn = 176;
private static final int opc_return = 177;
private static final int opc_getstatic = 178;
private static final int opc_putstatic = 179;
private static final int opc_getfield = 180;
private static final int opc_putfield = 181;
private static final int opc_invokevirtual = 182;
private static final int opc_invokespecial = 183;
private static final int opc_invokestatic = 184;
private static final int opc_invokeinterface = 185;
private static final int opc_new = 187;
// private static final int opc_newarray = 188;
private static final int opc_anewarray = 189;
// private static final int opc_arraylength = 190;
private static final int opc_athrow = 191;
private static final int opc_checkcast = 192;
// private static final int opc_instanceof = 193;
// private static final int opc_monitorenter = 194;
// private static final int opc_monitorexit = 195;
private static final int opc_wide = 196;
// private static final int opc_multianewarray = 197;
// private static final int opc_ifnull = 198;
// private static final int opc_ifnonnull = 199;
// private static final int opc_goto_w = 200;
// private static final int opc_jsr_w = 201;
// end of constants copied from sun.tools.java.RuntimeConstants
/** name of the superclass of proxy classes */
private String superclassName;
/** name of field for storing a proxy instance's invocation handler */
private final static String handlerFieldName = "h";
/** debugging flag for saving generated class files */
private final static boolean saveGeneratedFiles =
java.security.AccessController.doPrivileged(
new GetBooleanAction(
"sun.misc.ProxyGeneratorEx.saveGeneratedFiles")).booleanValue();
/**
* Generate a proxy class given a name and a list of proxy interfaces.
*/
public static byte[] generateProxyClass(final String name, Class superclass,
Class[] interfaces)
{
ProxyGeneratorEx gen = new ProxyGeneratorEx(name, superclass, interfaces);
final byte[] classFile = gen.generateClassFile();
if (saveGeneratedFiles) {
java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction<Void>() {
public Void run() {
try {
FileOutputStream file =
new FileOutputStream(dotToSlash(name) + ".class");
file.write(classFile);
file.close();
return null;
} catch (IOException e) {
throw new InternalError(
"I/O exception saving generated file: " + e);
}
}
});
}
return classFile;
}
/* preloaded Method objects for methods in java.lang.Object */
private static Method hashCodeMethod;
private static Method equalsMethod;
private static Method toStringMethod;
static {
try {
hashCodeMethod = Object.class.getMethod("hashCode");
equalsMethod =
Object.class.getMethod("equals", new Class[] { Object.class });
toStringMethod = Object.class.getMethod("toString");
} catch (NoSuchMethodException e) {
throw new NoSuchMethodError(e.getMessage());
}
}
/** name of proxy class */
private String className;
/** proxy interfaces */
private Class[] interfaces;
/** constant pool of class being generated */
private ConstantPool cp = new ConstantPool();
/** FieldInfo struct for each field of generated class */
private List<FieldInfo> fields = new ArrayList<FieldInfo>();
/** MethodInfo struct for each method of generated class */
private List<MethodInfo> methods = new ArrayList<MethodInfo>();
/**
* maps method signature string to list of ProxyMethod objects for
* proxy methods with that signature
*/
private Map<String, List<ProxyMethod>> proxyMethods =
new HashMap<String,List<ProxyMethod>>();
/** count of ProxyMethod objects added to proxyMethods */
private int proxyMethodCount = 0;
private Class superclass;
/**
* Construct a ProxyGeneratorEx to generate a proxy class with the
* specified name and for the given interfaces.
*
* A ProxyGeneratorEx object contains the state for the ongoing
* generation of a particular proxy class.
*/
private ProxyGeneratorEx(String className, Class supperclass, Class[] interfaces) {
this.className = className;
this.superclassName = dotToSlash(supperclass.getName());
this.superclass = supperclass;
this.interfaces = interfaces;
}
/**
* Generate a class file for the proxy class. This method drives the
* class file generation process.
*/
private byte[] generateClassFile() {
/* ============================================================
* Step 1: Assemble ProxyMethod objects for all methods to
* generate proxy dispatching code for.
*/
/*
* Record that proxy methods are needed for the hashCode, equals,
* and toString methods of java.lang.Object. This is done before
* the methods from the proxy interfaces so that the methods from
* java.lang.Object take precedence over duplicate methods in the
* proxy interfaces.
*/
addProxyMethod(hashCodeMethod, Object.class);
addProxyMethod(equalsMethod, Object.class);
addProxyMethod(toStringMethod, Object.class);
/*
* Now record all of the methods from the proxy interfaces, giving
* earlier interfaces precedence over later ones with duplicate
* methods.
*/
for (int i = 0; i < interfaces.length; i++) {
Method[] methods = interfaces[i].getMethods();
for (int j = 0; j < methods.length; j++) {
addProxyMethod(methods[j], interfaces[i]);
}
}
// Now record all of the methods from the proxy superclass
Method[] superclassMethods = superclass.getDeclaredMethods();
for (int j = 0; j < superclassMethods.length; j++) {
addProxyMethod(superclassMethods[j], superclass);
}
/*
* For each set of proxy methods with the same signature,
* verify that the methods' return types are compatible.
*/
for (List<ProxyMethod> sigmethods : proxyMethods.values()) {
checkReturnTypes(sigmethods);
}
/* ============================================================
* Step 2: Assemble FieldInfo and MethodInfo structs for all of
* fields and methods in the class we are generating.
*/
try {
methods.add(generateConstructor());
for (List<ProxyMethod> sigmethods : proxyMethods.values()) {
for (ProxyMethod pm : sigmethods) {
// add static field for method's Method object
fields.add(new FieldInfo(pm.methodFieldName,
"Ljava/lang/reflect/Method;",
ACC_PRIVATE | ACC_STATIC));
// generate code for proxy method and add it
methods.add(pm.generateMethod());
}
}
// add field: InvocationHandler
fields.add(new FieldInfo(handlerFieldName,
"Ljava/lang/reflect/InvocationHandler;",
ACC_PRIVATE));
methods.add(generateStaticInitializer());
} catch (IOException e) {
throw new InternalError("unexpected I/O Exception");
}
if (methods.size() > 65535) {
throw new IllegalArgumentException("method limit exceeded");
}
if (fields.size() > 65535) {
throw new IllegalArgumentException("field limit exceeded");
}
/* ============================================================
* Step 3: Write the final class file.
*/
/*
* Make sure that constant pool indexes are reserved for the
* following items before starting to write the final class file.
*/
cp.getClass(dotToSlash(className));
cp.getClass(superclassName);
for (int i = 0; i < interfaces.length; i++) {
cp.getClass(dotToSlash(interfaces[i].getName()));
}
/*
* Disallow new constant pool additions beyond this point, since
* we are about to write the final constant pool table.
*/
cp.setReadOnly();
ByteArrayOutputStream bout = new ByteArrayOutputStream();
DataOutputStream dout = new DataOutputStream(bout);
try {
/*
* Write all the items of the "ClassFile" structure.
* See JVMS section 4.1.
*/
// u4 magic;
dout.writeInt(0xCAFEBABE);
// u2 minor_version;
dout.writeShort(CLASSFILE_MINOR_VERSION);
// u2 major_version;
dout.writeShort(CLASSFILE_MAJOR_VERSION);
cp.write(dout); // (write constant pool)
// u2 access_flags;
dout.writeShort(ACC_PUBLIC | ACC_FINAL | ACC_SUPER);
// u2 this_class;
dout.writeShort(cp.getClass(dotToSlash(className)));
// u2 super_class;
dout.writeShort(cp.getClass(superclassName));
// u2 interfaces_count;
dout.writeShort(interfaces.length);
// u2 interfaces[interfaces_count];
for (int i = 0; i < interfaces.length; i++) {
dout.writeShort(cp.getClass(
dotToSlash(interfaces[i].getName())));
}
// u2 fields_count;
dout.writeShort(fields.size());
// field_info fields[fields_count];
for (FieldInfo f : fields) {
f.write(dout);
}
// u2 methods_count;
dout.writeShort(methods.size());
// method_info methods[methods_count];
for (MethodInfo m : methods) {
m.write(dout);
}
// u2 attributes_count;
dout.writeShort(0); // (no ClassFile attributes for proxy classes)
} catch (IOException e) {
throw new InternalError("unexpected I/O Exception");
}
return bout.toByteArray();
}
/**
* Add another method to be proxied, either by creating a new
* ProxyMethod object or augmenting an old one for a duplicate
* method.
*
* "fromClass" indicates the proxy interface that the method was
* found through, which may be different from (a subinterface of)
* the method's "declaring class". Note that the first Method
* object passed for a given name and descriptor identifies the
* Method object (and thus the declaring class) that will be
* passed to the invocation handler's "invoke" method for a given
* set of duplicate methods.
*/
private void addProxyMethod(Method m, Class fromClass) {
String name = m.getName();
Class[] parameterTypes = m.getParameterTypes();
Class returnType = m.getReturnType();
Class[] exceptionTypes = m.getExceptionTypes();
String sig = name + getParameterDescriptors(parameterTypes);
List<ProxyMethod> sigmethods = proxyMethods.get(sig);
if (sigmethods != null) {
for (ProxyMethod pm : sigmethods) {
if (returnType == pm.returnType) {
/*
* Found a match: reduce exception types to the
* greatest set of exceptions that can thrown
* compatibly with the throws clauses of both
* overridden methods.
*/
List<Class<?>> legalExceptions = new ArrayList<Class<?>>();
collectCompatibleTypes(
exceptionTypes, pm.exceptionTypes, legalExceptions);
collectCompatibleTypes(
pm.exceptionTypes, exceptionTypes, legalExceptions);
pm.exceptionTypes = new Class[legalExceptions.size()];
pm.exceptionTypes =
legalExceptions.toArray(pm.exceptionTypes);
return;
}
}
} else {
sigmethods = new ArrayList<ProxyMethod>(3);
proxyMethods.put(sig, sigmethods);
}
sigmethods.add(new ProxyMethod(name, parameterTypes, returnType,
exceptionTypes, fromClass));
}
/**
* For a given set of proxy methods with the same signature, check
* that their return types are compatible according to the Proxy
* specification.
*
* Specifically, if there is more than one such method, then all
* of the return types must be reference types, and there must be
* one return type that is assignable to each of the rest of them.
*/
private static void checkReturnTypes(List<ProxyMethod> methods) {
/*
* If there is only one method with a given signature, there
* cannot be a conflict. This is the only case in which a
* primitive (or void) return type is allowed.
*/
if (methods.size() < 2) {
return;
}
/*
* List of return types that are not yet known to be
* assignable from ("covered" by) any of the others.
*/
LinkedList<Class<?>> uncoveredReturnTypes = new LinkedList<Class<?>>();
nextNewReturnType:
for (ProxyMethod pm : methods) {
Class<?> newReturnType = pm.returnType;
if (newReturnType.isPrimitive()) {
throw new IllegalArgumentException(
"methods with same signature " +
getFriendlyMethodSignature(pm.methodName,
pm.parameterTypes) +
" but incompatible return types: " +
newReturnType.getName() + " and others");
}
boolean added = false;
/*
* Compare the new return type to the existing uncovered
* return types.
*/
ListIterator<Class<?>> liter = uncoveredReturnTypes.listIterator();
while (liter.hasNext()) {
Class<?> uncoveredReturnType = liter.next();
/*
* If an existing uncovered return type is assignable
* to this new one, then we can forget the new one.
*/
if (newReturnType.isAssignableFrom(uncoveredReturnType)) {
assert !added;
continue nextNewReturnType;
}
/*
* If the new return type is assignable to an existing
* uncovered one, then should replace the existing one
* with the new one (or just forget the existing one,
* if the new one has already be put in the list).
*/
if (uncoveredReturnType.isAssignableFrom(newReturnType)) {
// (we can assume that each return type is unique)
if (!added) {
liter.set(newReturnType);
added = true;
} else {
liter.remove();
}
}
}
/*
* If we got through the list of existing uncovered return
* types without an assignability relationship, then add
* the new return type to the list of uncovered ones.
*/
if (!added) {
uncoveredReturnTypes.add(newReturnType);
}
}
/*
* We shouldn't end up with more than one return type that is
* not assignable from any of the others.
*/
if (uncoveredReturnTypes.size() > 1) {
ProxyMethod pm = methods.get(0);
throw new IllegalArgumentException(
"methods with same signature " +
getFriendlyMethodSignature(pm.methodName, pm.parameterTypes) +
" but incompatible return types: " + uncoveredReturnTypes);
}
}
/**
* A FieldInfo object contains information about a particular field
* in the class being generated. The class mirrors the data items of
* the "field_info" structure of the class file format (see JVMS 4.5).
*/
private class FieldInfo {
public int accessFlags;
public String name;
public String descriptor;
public FieldInfo(String name, String descriptor, int accessFlags) {
this.name = name;
this.descriptor = descriptor;
this.accessFlags = accessFlags;
/*
* Make sure that constant pool indexes are reserved for the
* following items before starting to write the final class file.
*/
cp.getUtf8(name);
cp.getUtf8(descriptor);
}
public void write(DataOutputStream out) throws IOException {
/*
* Write all the items of the "field_info" structure.
* See JVMS section 4.5.
*/
// u2 access_flags;
out.writeShort(accessFlags);
// u2 name_index;
out.writeShort(cp.getUtf8(name));
// u2 descriptor_index;
out.writeShort(cp.getUtf8(descriptor));
// u2 attributes_count;
out.writeShort(0); // (no field_info attributes for proxy classes)
}
}
/**
* An ExceptionTableEntry object holds values for the data items of
* an entry in the "exception_table" item of the "Code" attribute of
* "method_info" structures (see JVMS 4.7.3).
*/
private static class ExceptionTableEntry {
public short startPc;
public short endPc;
public short handlerPc;
public short catchType;
public ExceptionTableEntry(short startPc, short endPc,
short handlerPc, short catchType)
{
this.startPc = startPc;
this.endPc = endPc;
this.handlerPc = handlerPc;
this.catchType = catchType;
}
};
/**
* A MethodInfo object contains information about a particular method
* in the class being generated. This class mirrors the data items of
* the "method_info" structure of the class file format (see JVMS 4.6).
*/
private class MethodInfo {
public int accessFlags;
public String name;
public String descriptor;
public short maxStack;
public short maxLocals;
public ByteArrayOutputStream code = new ByteArrayOutputStream();
public List<ExceptionTableEntry> exceptionTable =
new ArrayList<ExceptionTableEntry>();
public short[] declaredExceptions;
public MethodInfo(String name, String descriptor, int accessFlags) {
this.name = name;
this.descriptor = descriptor;
this.accessFlags = accessFlags;
/*
* Make sure that constant pool indexes are reserved for the
* following items before starting to write the final class file.
*/
cp.getUtf8(name);
cp.getUtf8(descriptor);
cp.getUtf8("Code");
cp.getUtf8("Exceptions");
}
public void write(DataOutputStream out) throws IOException {
/*
* Write all the items of the "method_info" structure.
* See JVMS section 4.6.
*/
// u2 access_flags;
out.writeShort(accessFlags);
// u2 name_index;
out.writeShort(cp.getUtf8(name));
// u2 descriptor_index;
out.writeShort(cp.getUtf8(descriptor));
// u2 attributes_count;
out.writeShort(2); // (two method_info attributes:)
// Write "Code" attribute. See JVMS section 4.7.3.
// u2 attribute_name_index;
out.writeShort(cp.getUtf8("Code"));
// u4 attribute_length;
out.writeInt(12 + code.size() + 8 * exceptionTable.size());
// u2 max_stack;
out.writeShort(maxStack);
// u2 max_locals;
out.writeShort(maxLocals);
// u2 code_length;
out.writeInt(code.size());
// u1 code[code_length];
code.writeTo(out);
// u2 exception_table_length;
out.writeShort(exceptionTable.size());
for (ExceptionTableEntry e : exceptionTable) {
// u2 start_pc;
out.writeShort(e.startPc);
// u2 end_pc;
out.writeShort(e.endPc);
// u2 handler_pc;
out.writeShort(e.handlerPc);
// u2 catch_type;
out.writeShort(e.catchType);
}
// u2 attributes_count;
out.writeShort(0);
// write "Exceptions" attribute. See JVMS section 4.7.4.
// u2 attribute_name_index;
out.writeShort(cp.getUtf8("Exceptions"));
// u4 attributes_length;
out.writeInt(2 + 2 * declaredExceptions.length);
// u2 number_of_exceptions;
out.writeShort(declaredExceptions.length);
// u2 exception_index_table[number_of_exceptions];
for (int i = 0; i < declaredExceptions.length; i++) {
out.writeShort(declaredExceptions[i]);
}
}
}
/**
* A ProxyMethod object represents a proxy method in the proxy class
* being generated: a method whose implementation will encode and
* dispatch invocations to the proxy instance's invocation handler.
*/
private class ProxyMethod {
public String methodName;
public Class[] parameterTypes;
public Class returnType;
public Class[] exceptionTypes;
public Class fromClass;
public String methodFieldName;
private ProxyMethod(String methodName, Class[] parameterTypes,
Class returnType, Class[] exceptionTypes,
Class fromClass)
{
this.methodName = methodName;
this.parameterTypes = parameterTypes;
this.returnType = returnType;
this.exceptionTypes = exceptionTypes;
this.fromClass = fromClass;
this.methodFieldName = "m" + proxyMethodCount++;
}
/**
* Return a MethodInfo object for this method, including generating
* the code and exception table entry.
*/
private MethodInfo generateMethod() throws IOException {
String desc = getMethodDescriptor(parameterTypes, returnType);
MethodInfo minfo = new MethodInfo(methodName, desc,
ACC_PUBLIC | ACC_FINAL);
int[] parameterSlot = new int[parameterTypes.length];
int nextSlot = 1;
for (int i = 0; i < parameterSlot.length; i++) {
parameterSlot[i] = nextSlot;
nextSlot += getWordsPerType(parameterTypes[i]);
}
int localSlot0 = nextSlot;
short pc, tryBegin = 0, tryEnd;
DataOutputStream out = new DataOutputStream(minfo.code);
code_aload(0, out);
out.writeByte(opc_getfield);
out.writeShort(cp.getFieldRef(
className,
handlerFieldName, "Ljava/lang/reflect/InvocationHandler;"));
code_aload(0, out);
out.writeByte(opc_getstatic);
out.writeShort(cp.getFieldRef(
dotToSlash(className),
methodFieldName, "Ljava/lang/reflect/Method;"));
if (parameterTypes.length > 0) {
code_ipush(parameterTypes.length, out);
out.writeByte(opc_anewarray);
out.writeShort(cp.getClass("java/lang/Object"));
for (int i = 0; i < parameterTypes.length; i++) {
out.writeByte(opc_dup);
code_ipush(i, out);
codeWrapArgument(parameterTypes[i], parameterSlot[i], out);
out.writeByte(opc_aastore);
}
} else {
out.writeByte(opc_aconst_null);
}
out.writeByte(opc_invokeinterface);
out.writeShort(cp.getInterfaceMethodRef(
"java/lang/reflect/InvocationHandler",
"invoke",
"(Ljava/lang/Object;Ljava/lang/reflect/Method;" +
"[Ljava/lang/Object;)Ljava/lang/Object;"));
out.writeByte(4);
out.writeByte(0);
if (returnType == void.class) {
out.writeByte(opc_pop);
out.writeByte(opc_return);
} else {
codeUnwrapReturnValue(returnType, out);
}
tryEnd = pc = (short) minfo.code.size();
List<Class<?>> catchList = computeUniqueCatchList(exceptionTypes);
if (catchList.size() > 0) {
for (Class<?> ex : catchList) {
minfo.exceptionTable.add(new ExceptionTableEntry(
tryBegin, tryEnd, pc,
cp.getClass(dotToSlash(ex.getName()))));
}
out.writeByte(opc_athrow);
pc = (short) minfo.code.size();
minfo.exceptionTable.add(new ExceptionTableEntry(
tryBegin, tryEnd, pc, cp.getClass("java/lang/Throwable")));
code_astore(localSlot0, out);
out.writeByte(opc_new);
out.writeShort(cp.getClass(
"java/lang/reflect/UndeclaredThrowableException"));
out.writeByte(opc_dup);
code_aload(localSlot0, out);
out.writeByte(opc_invokespecial);
out.writeShort(cp.getMethodRef(
"java/lang/reflect/UndeclaredThrowableException",
"<init>", "(Ljava/lang/Throwable;)V"));
out.writeByte(opc_athrow);
}
if (minfo.code.size() > 65535) {
throw new IllegalArgumentException("code size limit exceeded");
}
minfo.maxStack = 10;
minfo.maxLocals = (short) (localSlot0 + 1);
minfo.declaredExceptions = new short[exceptionTypes.length];
for (int i = 0; i < exceptionTypes.length; i++) {
minfo.declaredExceptions[i] = cp.getClass(
dotToSlash(exceptionTypes[i].getName()));
}
return minfo;
}
/**
* Generate code for wrapping an argument of the given type
* whose value can be found at the specified local variable
* index, in order for it to be passed (as an Object) to the
* invocation handler's "invoke" method. The code is written
* to the supplied stream.
*/
private void codeWrapArgument(Class type, int slot,
DataOutputStream out)
throws IOException
{
if (type.isPrimitive()) {
PrimitiveTypeInfo prim = PrimitiveTypeInfo.get(type);
if (type == int.class ||
type == boolean.class ||
type == byte.class ||
type == char.class ||
type == short.class)
{
code_iload(slot, out);
} else if (type == long.class) {
code_lload(slot, out);
} else if (type == float.class) {
code_fload(slot, out);
} else if (type == double.class) {
code_dload(slot, out);
} else {
throw new AssertionError();
}
out.writeByte(opc_invokestatic);
out.writeShort(cp.getMethodRef(
prim.wrapperClassName,
"valueOf", prim.wrapperValueOfDesc));
} else {
code_aload(slot, out);
}
}
/**
* Generate code for unwrapping a return value of the given
* type from the invocation handler's "invoke" method (as type
* Object) to its correct type. The code is written to the
* supplied stream.
*/
private void codeUnwrapReturnValue(Class type, DataOutputStream out)
throws IOException
{
if (type.isPrimitive()) {
PrimitiveTypeInfo prim = PrimitiveTypeInfo.get(type);
out.writeByte(opc_checkcast);
out.writeShort(cp.getClass(prim.wrapperClassName));
out.writeByte(opc_invokevirtual);
out.writeShort(cp.getMethodRef(
prim.wrapperClassName,
prim.unwrapMethodName, prim.unwrapMethodDesc));
if (type == int.class ||
type == boolean.class ||
type == byte.class ||
type == char.class ||
type == short.class)
{
out.writeByte(opc_ireturn);
} else if (type == long.class) {
out.writeByte(opc_lreturn);
} else if (type == float.class) {
out.writeByte(opc_freturn);
} else if (type == double.class) {
out.writeByte(opc_dreturn);
} else {
throw new AssertionError();
}
} else {
out.writeByte(opc_checkcast);
out.writeShort(cp.getClass(dotToSlash(type.getName())));
out.writeByte(opc_areturn);
}
}
/**
* Generate code for initializing the static field that stores
* the Method object for this proxy method. The code is written
* to the supplied stream.
*/
private void codeFieldInitialization(DataOutputStream out)
throws IOException
{
codeClassForName(fromClass, out);
code_ldc(cp.getString(methodName), out);
code_ipush(parameterTypes.length, out);
out.writeByte(opc_anewarray);
out.writeShort(cp.getClass("java/lang/Class"));
for (int i = 0; i < parameterTypes.length; i++) {
out.writeByte(opc_dup);
code_ipush(i, out);
if (parameterTypes[i].isPrimitive()) {
PrimitiveTypeInfo prim =
PrimitiveTypeInfo.get(parameterTypes[i]);
out.writeByte(opc_getstatic);
out.writeShort(cp.getFieldRef(
prim.wrapperClassName, "TYPE", "Ljava/lang/Class;"));
} else {
codeClassForName(parameterTypes[i], out);
}
out.writeByte(opc_aastore);
}
out.writeByte(opc_invokevirtual);
out.writeShort(cp.getMethodRef(
"java/lang/Class",
"getMethod",
"(Ljava/lang/String;[Ljava/lang/Class;)" +
"Ljava/lang/reflect/Method;"));
out.writeByte(opc_putstatic);
out.writeShort(cp.getFieldRef(
dotToSlash(className),
methodFieldName, "Ljava/lang/reflect/Method;"));
}
}
/**
* Generate the constructor method for the proxy class.
*/
private MethodInfo generateConstructor() throws IOException {
MethodInfo minfo = new MethodInfo(
"<init>", "(Ljava/lang/reflect/InvocationHandler;)V",
ACC_PUBLIC);
DataOutputStream out = new DataOutputStream(minfo.code);
code_aload(0, out);
out.writeByte(opc_invokespecial);
out.writeShort(cp.getMethodRef(
superclassName,
"<init>", "()V"));
code_aload(0, out);
code_aload(1, out);
// write field h
out.writeByte(opc_putfield);
out.writeShort(cp.getFieldRef(className, handlerFieldName, "Ljava/lang/reflect/InvocationHandler;"));
out.writeByte(opc_return);
minfo.maxStack = 10;
minfo.maxLocals = 2;
minfo.declaredExceptions = new short[0];
return minfo;
}
/**
* Generate the static initializer method for the proxy class.
*/
private MethodInfo generateStaticInitializer() throws IOException {
MethodInfo minfo = new MethodInfo(
"<clinit>", "()V", ACC_STATIC);
int localSlot0 = 1;
short pc, tryBegin = 0, tryEnd;
DataOutputStream out = new DataOutputStream(minfo.code);
for (List<ProxyMethod> sigmethods : proxyMethods.values()) {
for (ProxyMethod pm : sigmethods) {
pm.codeFieldInitialization(out);
}
}
out.writeByte(opc_return);
tryEnd = pc = (short) minfo.code.size();
minfo.exceptionTable.add(new ExceptionTableEntry(
tryBegin, tryEnd, pc,
cp.getClass("java/lang/NoSuchMethodException")));
code_astore(localSlot0, out);
out.writeByte(opc_new);
out.writeShort(cp.getClass("java/lang/NoSuchMethodError"));
out.writeByte(opc_dup);
code_aload(localSlot0, out);
out.writeByte(opc_invokevirtual);
out.writeShort(cp.getMethodRef(
"java/lang/Throwable", "getMessage", "()Ljava/lang/String;"));
out.writeByte(opc_invokespecial);
out.writeShort(cp.getMethodRef(
"java/lang/NoSuchMethodError", "<init>", "(Ljava/lang/String;)V"));
out.writeByte(opc_athrow);
pc = (short) minfo.code.size();
minfo.exceptionTable.add(new ExceptionTableEntry(
tryBegin, tryEnd, pc,
cp.getClass("java/lang/ClassNotFoundException")));
code_astore(localSlot0, out);
out.writeByte(opc_new);
out.writeShort(cp.getClass("java/lang/NoClassDefFoundError"));
out.writeByte(opc_dup);
code_aload(localSlot0, out);
out.writeByte(opc_invokevirtual);
out.writeShort(cp.getMethodRef(
"java/lang/Throwable", "getMessage", "()Ljava/lang/String;"));
out.writeByte(opc_invokespecial);
out.writeShort(cp.getMethodRef(
"java/lang/NoClassDefFoundError",
"<init>", "(Ljava/lang/String;)V"));
out.writeByte(opc_athrow);
if (minfo.code.size() > 65535) {
throw new IllegalArgumentException("code size limit exceeded");
}
minfo.maxStack = 10;
minfo.maxLocals = (short) (localSlot0 + 1);
minfo.declaredExceptions = new short[0];
return minfo;
}
/*
* =============== Code Generation Utility Methods ===============
*/
/*
* The following methods generate code for the load or store operation
* indicated by their name for the given local variable. The code is
* written to the supplied stream.
*/
private void code_iload(int lvar, DataOutputStream out)
throws IOException
{
codeLocalLoadStore(lvar, opc_iload, opc_iload_0, out);
}
private void code_lload(int lvar, DataOutputStream out)
throws IOException
{
codeLocalLoadStore(lvar, opc_lload, opc_lload_0, out);
}
private void code_fload(int lvar, DataOutputStream out)
throws IOException
{
codeLocalLoadStore(lvar, opc_fload, opc_fload_0, out);
}
private void code_dload(int lvar, DataOutputStream out)
throws IOException
{
codeLocalLoadStore(lvar, opc_dload, opc_dload_0, out);
}
private void code_aload(int lvar, DataOutputStream out)
throws IOException
{
codeLocalLoadStore(lvar, opc_aload, opc_aload_0, out);
}
// private void code_istore(int lvar, DataOutputStream out)
// throws IOException
// {
// codeLocalLoadStore(lvar, opc_istore, opc_istore_0, out);
// }
// private void code_lstore(int lvar, DataOutputStream out)
// throws IOException
// {
// codeLocalLoadStore(lvar, opc_lstore, opc_lstore_0, out);
// }
// private void code_fstore(int lvar, DataOutputStream out)
// throws IOException
// {
// codeLocalLoadStore(lvar, opc_fstore, opc_fstore_0, out);
// }
// private void code_dstore(int lvar, DataOutputStream out)
// throws IOException
// {
// codeLocalLoadStore(lvar, opc_dstore, opc_dstore_0, out);
// }
private void code_astore(int lvar, DataOutputStream out)
throws IOException
{
codeLocalLoadStore(lvar, opc_astore, opc_astore_0, out);
}
/**
* Generate code for a load or store instruction for the given local
* variable. The code is written to the supplied stream.
*
* "opcode" indicates the opcode form of the desired load or store
* instruction that takes an explicit local variable index, and
* "opcode_0" indicates the corresponding form of the instruction
* with the implicit index 0.
*/
private void codeLocalLoadStore(int lvar, int opcode, int opcode_0,
DataOutputStream out)
throws IOException
{
assert lvar >= 0 && lvar <= 0xFFFF;
if (lvar <= 3) {
out.writeByte(opcode_0 + lvar);
} else if (lvar <= 0xFF) {
out.writeByte(opcode);
out.writeByte(lvar & 0xFF);
} else {
/*
* Use the "wide" instruction modifier for local variable
* indexes that do not fit into an unsigned byte.
*/
out.writeByte(opc_wide);
out.writeByte(opcode);
out.writeShort(lvar & 0xFFFF);
}
}
/**
* Generate code for an "ldc" instruction for the given constant pool
* index (the "ldc_w" instruction is used if the index does not fit
* into an unsigned byte). The code is written to the supplied stream.
*/
private void code_ldc(int index, DataOutputStream out)
throws IOException
{
assert index >= 0 && index <= 0xFFFF;
if (index <= 0xFF) {
out.writeByte(opc_ldc);
out.writeByte(index & 0xFF);
} else {
out.writeByte(opc_ldc_w);
out.writeShort(index & 0xFFFF);
}
}
/**
* Generate code to push a constant integer value on to the operand
* stack, using the "iconst_<i>", "bipush", or "sipush" instructions
* depending on the size of the value. The code is written to the
* supplied stream.
*/
private void code_ipush(int value, DataOutputStream out)
throws IOException
{
if (value >= -1 && value <= 5) {
out.writeByte(opc_iconst_0 + value);
} else if (value >= Byte.MIN_VALUE && value <= Byte.MAX_VALUE) {
out.writeByte(opc_bipush);
out.writeByte(value & 0xFF);
} else if (value >= Short.MIN_VALUE && value <= Short.MAX_VALUE) {
out.writeByte(opc_sipush);
out.writeShort(value & 0xFFFF);
} else {
throw new AssertionError();
}
}
/**
* Generate code to invoke the Class.forName with the name of the given
* class to get its Class object at runtime. The code is written to
* the supplied stream. Note that the code generated by this method
* may caused the checked ClassNotFoundException to be thrown.
*/
private void codeClassForName(Class cl, DataOutputStream out)
throws IOException
{
code_ldc(cp.getString(cl.getName()), out);
out.writeByte(opc_invokestatic);
out.writeShort(cp.getMethodRef(
"java/lang/Class",
"forName", "(Ljava/lang/String;)Ljava/lang/Class;"));
}
/*
* ==================== General Utility Methods ====================
*/
/**
* Convert a fully qualified class name that uses '.' as the package
* separator, the external representation used by the Java language
* and APIs, to a fully qualified class name that uses '/' as the
* package separator, the representation used in the class file
* format (see JVMS section 4.2).
*/
private static String dotToSlash(String name) {
return name.replace('.', '/');
}
/**
* Return the "method descriptor" string for a method with the given
* parameter types and return type. See JVMS section 4.3.3.
*/
private static String getMethodDescriptor(Class[] parameterTypes,
Class returnType)
{
return getParameterDescriptors(parameterTypes) +
((returnType == void.class) ? "V" : getFieldType(returnType));
}
/**
* Return the list of "parameter descriptor" strings enclosed in
* parentheses corresponding to the given parameter types (in other
* words, a method descriptor without a return descriptor). This
* string is useful for constructing string keys for methods without
* regard to their return type.
*/
private static String getParameterDescriptors(Class[] parameterTypes) {
StringBuilder desc = new StringBuilder("(");
for (int i = 0; i < parameterTypes.length; i++) {
desc.append(getFieldType(parameterTypes[i]));
}
desc.append(')');
return desc.toString();
}
/**
* Return the "field type" string for the given type, appropriate for
* a field descriptor, a parameter descriptor, or a return descriptor
* other than "void". See JVMS section 4.3.2.
*/
private static String getFieldType(Class type) {
if (type.isPrimitive()) {
return PrimitiveTypeInfo.get(type).baseTypeString;
} else if (type.isArray()) {
/*
* According to JLS 20.3.2, the getName() method on Class does
* return the VM type descriptor format for array classes (only);
* using that should be quicker than the otherwise obvious code:
*
* return "[" + getTypeDescriptor(type.getComponentType());
*/
return type.getName().replace('.', '/');
} else {
return "L" + dotToSlash(type.getName()) + ";";
}
}
/**
* Returns a human-readable string representing the signature of a
* method with the given name and parameter types.
*/
private static String getFriendlyMethodSignature(String name,
Class[] parameterTypes)
{
StringBuilder sig = new StringBuilder(name);
sig.append('(');
for (int i = 0; i < parameterTypes.length; i++) {
if (i > 0) {
sig.append(',');
}
Class parameterType = parameterTypes[i];
int dimensions = 0;
while (parameterType.isArray()) {
parameterType = parameterType.getComponentType();
dimensions++;
}
sig.append(parameterType.getName());
while (dimensions-- > 0) {
sig.append("[]");
}
}
sig.append(')');
return sig.toString();
}
/**
* Return the number of abstract "words", or consecutive local variable
* indexes, required to contain a value of the given type. See JVMS
* section 3.6.1.
*
* Note that the original version of the JVMS contained a definition of
* this abstract notion of a "word" in section 3.4, but that definition
* was removed for the second edition.
*/
private static int getWordsPerType(Class type) {
if (type == long.class || type == double.class) {
return 2;
} else {
return 1;
}
}
/**
* Add to the given list all of the types in the "from" array that
* are not already contained in the list and are assignable to at
* least one of the types in the "with" array.
*
* This method is useful for computing the greatest common set of
* declared exceptions from duplicate methods inherited from
* different interfaces.
*/
private static void collectCompatibleTypes(Class<?>[] from,
Class<?>[] with,
List<Class<?>> list)
{
for (int i = 0; i < from.length; i++) {
if (!list.contains(from[i])) {
for (int j = 0; j < with.length; j++) {
if (with[j].isAssignableFrom(from[i])) {
list.add(from[i]);
break;
}
}
}
}
}
/**
* Given the exceptions declared in the throws clause of a proxy method,
* compute the exceptions that need to be caught from the invocation
* handler's invoke method and rethrown intact in the method's
* implementation before catching other Throwables and wrapping them
* in UndeclaredThrowableExceptions.
*
* The exceptions to be caught are returned in a List object. Each
* exception in the returned list is guaranteed to not be a subclass of
* any of the other exceptions in the list, so the catch blocks for
* these exceptions may be generated in any order relative to each other.
*
* Error and RuntimeException are each always contained by the returned
* list (if none of their superclasses are contained), since those
* unchecked exceptions should always be rethrown intact, and thus their
* subclasses will never appear in the returned list.
*
* The returned List will be empty if java.lang.Throwable is in the
* given list of declared exceptions, indicating that no exceptions
* need to be caught.
*/
private static List<Class<?>> computeUniqueCatchList(Class<?>[] exceptions) {
List<Class<?>> uniqueList = new ArrayList<Class<?>>();
// unique exceptions to catch
uniqueList.add(Error.class); // always catch/rethrow these
uniqueList.add(RuntimeException.class);
nextException:
for (int i = 0; i < exceptions.length; i++) {
Class<?> ex = exceptions[i];
if (ex.isAssignableFrom(Throwable.class)) {
/*
* If Throwable is declared to be thrown by the proxy method,
* then no catch blocks are necessary, because the invoke
* can, at most, throw Throwable anyway.
*/
uniqueList.clear();
break;
} else if (!Throwable.class.isAssignableFrom(ex)) {
/*
* Ignore types that cannot be thrown by the invoke method.
*/
continue;
}
/*
* Compare this exception against the current list of
* exceptions that need to be caught:
*/
for (int j = 0; j < uniqueList.size();) {
Class<?> ex2 = uniqueList.get(j);
if (ex2.isAssignableFrom(ex)) {
/*
* if a superclass of this exception is already on
* the list to catch, then ignore this one and continue;
*/
continue nextException;
} else if (ex.isAssignableFrom(ex2)) {
/*
* if a subclass of this exception is on the list
* to catch, then remove it;
*/
uniqueList.remove(j);
} else {
j++; // else continue comparing.
}
}
// This exception is unique (so far): add it to the list to catch.
uniqueList.add(ex);
}
return uniqueList;
}
/**
* A PrimitiveTypeInfo object contains assorted information about
* a primitive type in its public fields. The struct for a particular
* primitive type can be obtained using the static "get" method.
*/
private static class PrimitiveTypeInfo {
/** "base type" used in various descriptors (see JVMS section 4.3.2) */
public String baseTypeString;
/** name of corresponding wrapper class */
public String wrapperClassName;
/** method descriptor for wrapper class "valueOf" factory method */
public String wrapperValueOfDesc;
/** name of wrapper class method for retrieving primitive value */
public String unwrapMethodName;
/** descriptor of same method */
public String unwrapMethodDesc;
private static Map<Class,PrimitiveTypeInfo> table =
new HashMap<Class,PrimitiveTypeInfo>();
static {
add(byte.class, Byte.class);
add(char.class, Character.class);
add(double.class, Double.class);
add(float.class, Float.class);
add(int.class, Integer.class);
add(long.class, Long.class);
add(short.class, Short.class);
add(boolean.class, Boolean.class);
}
private static void add(Class primitiveClass, Class wrapperClass) {
table.put(primitiveClass,
new PrimitiveTypeInfo(primitiveClass, wrapperClass));
}
private PrimitiveTypeInfo(Class primitiveClass, Class wrapperClass) {
assert primitiveClass.isPrimitive();
baseTypeString =
Array.newInstance(primitiveClass, 0)
.getClass().getName().substring(1);
wrapperClassName = dotToSlash(wrapperClass.getName());
wrapperValueOfDesc =
"(" + baseTypeString + ")L" + wrapperClassName + ";";
unwrapMethodName = primitiveClass.getName() + "Value";
unwrapMethodDesc = "()" + baseTypeString;
}
public static PrimitiveTypeInfo get(Class cl) {
return table.get(cl);
}
}
/**
* A ConstantPool object represents the constant pool of a class file
* being generated. This representation of a constant pool is designed
* specifically for use by ProxyGeneratorEx; in particular, it assumes
* that constant pool entries will not need to be resorted (for example,
* by their type, as the Java compiler does), so that the final index
* value can be assigned and used when an entry is first created.
*
* Note that new entries cannot be created after the constant pool has
* been written to a class file. To prevent such logic errors, a
* ConstantPool instance can be marked "read only", so that further
* attempts to add new entries will fail with a runtime exception.
*
* See JVMS section 4.4 for more information about the constant pool
* of a class file.
*/
private static class ConstantPool {
/**
* list of constant pool entries, in constant pool index order.
*
* This list is used when writing the constant pool to a stream
* and for assigning the next index value. Note that element 0
* of this list corresponds to constant pool index 1.
*/
private List<Entry> pool = new ArrayList<Entry>(32);
/**
* maps constant pool data of all types to constant pool indexes.
*
* This map is used to look up the index of an existing entry for
* values of all types.
*/
private Map<Object,Short> map = new HashMap<Object,Short>(16);
/** true if no new constant pool entries may be added */
private boolean readOnly = false;
/**
* Get or assign the index for a CONSTANT_Utf8 entry.
*/
public short getUtf8(String s) {
if (s == null) {
throw new NullPointerException();
}
return getValue(s);
}
/**
* Get or assign the index for a CONSTANT_Integer entry.
*/
public short getInteger(int i) {
return getValue(new Integer(i));
}
/**
* Get or assign the index for a CONSTANT_Float entry.
*/
public short getFloat(float f) {
return getValue(new Float(f));
}
/**
* Get or assign the index for a CONSTANT_Class entry.
*/
public short getClass(String name) {
short utf8Index = getUtf8(name);
return getIndirect(new IndirectEntry(
CONSTANT_CLASS, utf8Index));
}
/**
* Get or assign the index for a CONSTANT_String entry.
*/
public short getString(String s) {
short utf8Index = getUtf8(s);
return getIndirect(new IndirectEntry(
CONSTANT_STRING, utf8Index));
}
/**
* Get or assign the index for a CONSTANT_FieldRef entry.
*/
public short getFieldRef(String className,
String name, String descriptor)
{
short classIndex = getClass(className);
short nameAndTypeIndex = getNameAndType(name, descriptor);
return getIndirect(new IndirectEntry(
CONSTANT_FIELD, classIndex, nameAndTypeIndex));
}
/**
* Get or assign the index for a CONSTANT_MethodRef entry.
*/
public short getMethodRef(String className,
String name, String descriptor)
{
short classIndex = getClass(className);
short nameAndTypeIndex = getNameAndType(name, descriptor);
return getIndirect(new IndirectEntry(
CONSTANT_METHOD, classIndex, nameAndTypeIndex));
}
/**
* Get or assign the index for a CONSTANT_InterfaceMethodRef entry.
*/
public short getInterfaceMethodRef(String className, String name,
String descriptor)
{
short classIndex = getClass(className);
short nameAndTypeIndex = getNameAndType(name, descriptor);
return getIndirect(new IndirectEntry(
CONSTANT_INTERFACEMETHOD, classIndex, nameAndTypeIndex));
}
/**
* Get or assign the index for a CONSTANT_NameAndType entry.
*/
public short getNameAndType(String name, String descriptor) {
short nameIndex = getUtf8(name);
short descriptorIndex = getUtf8(descriptor);
return getIndirect(new IndirectEntry(
CONSTANT_NAMEANDTYPE, nameIndex, descriptorIndex));
}
/**
* Set this ConstantPool instance to be "read only".
*
* After this method has been called, further requests to get
* an index for a non-existent entry will cause an InternalError
* to be thrown instead of creating of the entry.
*/
public void setReadOnly() {
readOnly = true;
}
/**
* Write this constant pool to a stream as part of
* the class file format.
*
* This consists of writing the "constant_pool_count" and
* "constant_pool[]" items of the "ClassFile" structure, as
* described in JVMS section 4.1.
*/
public void write(OutputStream out) throws IOException {
DataOutputStream dataOut = new DataOutputStream(out);
// constant_pool_count: number of entries plus one
dataOut.writeShort(pool.size() + 1);
for (Entry e : pool) {
e.write(dataOut);
}
}
/**
* Add a new constant pool entry and return its index.
*/
private short addEntry(Entry entry) {
pool.add(entry);
/*
* Note that this way of determining the index of the
* added entry is wrong if this pool supports
* CONSTANT_Long or CONSTANT_Double entries.
*/
if (pool.size() >= 65535) {
throw new IllegalArgumentException(
"constant pool size limit exceeded");
}
return (short) pool.size();
}
/**
* Get or assign the index for an entry of a type that contains
* a direct value. The type of the given object determines the
* type of the desired entry as follows:
*
* java.lang.String CONSTANT_Utf8
* java.lang.Integer CONSTANT_Integer
* java.lang.Float CONSTANT_Float
* java.lang.Long CONSTANT_Long
* java.lang.Double CONSTANT_DOUBLE
*/
private short getValue(Object key) {
Short index = map.get(key);
if (index != null) {
return index.shortValue();
} else {
if (readOnly) {
throw new InternalError(
"late constant pool addition: " + key);
}
short i = addEntry(new ValueEntry(key));
map.put(key, new Short(i));
return i;
}
}
/**
* Get or assign the index for an entry of a type that contains
* references to other constant pool entries.
*/
private short getIndirect(IndirectEntry e) {
Short index = map.get(e);
if (index != null) {
return index.shortValue();
} else {
if (readOnly) {
throw new InternalError("late constant pool addition");
}
short i = addEntry(e);
map.put(e, new Short(i));
return i;
}
}
/**
* Entry is the abstact superclass of all constant pool entry types
* that can be stored in the "pool" list; its purpose is to define a
* common method for writing constant pool entries to a class file.
*/
private static abstract class Entry {
public abstract void write(DataOutputStream out)
throws IOException;
}
/**
* ValueEntry represents a constant pool entry of a type that
* contains a direct value (see the comments for the "getValue"
* method for a list of such types).
*
* ValueEntry objects are not used as keys for their entries in the
* Map "map", so no useful hashCode or equals methods are defined.
*/
private static class ValueEntry extends Entry {
private Object value;
public ValueEntry(Object value) {
this.value = value;
}
public void write(DataOutputStream out) throws IOException {
if (value instanceof String) {
out.writeByte(CONSTANT_UTF8);
out.writeUTF((String) value);
} else if (value instanceof Integer) {
out.writeByte(CONSTANT_INTEGER);
out.writeInt(((Integer) value).intValue());
} else if (value instanceof Float) {
out.writeByte(CONSTANT_FLOAT);
out.writeFloat(((Float) value).floatValue());
} else if (value instanceof Long) {
out.writeByte(CONSTANT_LONG);
out.writeLong(((Long) value).longValue());
} else if (value instanceof Double) {
out.writeDouble(CONSTANT_DOUBLE);
out.writeDouble(((Double) value).doubleValue());
} else {
throw new InternalError("bogus value entry: " + value);
}
}
}
/**
* IndirectEntry represents a constant pool entry of a type that
* references other constant pool entries, i.e., the following types:
*
* CONSTANT_Class, CONSTANT_String, CONSTANT_Fieldref,
* CONSTANT_Methodref, CONSTANT_InterfaceMethodref, and
* CONSTANT_NameAndType.
*
* Each of these entry types contains either one or two indexes of
* other constant pool entries.
*
* IndirectEntry objects are used as the keys for their entries in
* the Map "map", so the hashCode and equals methods are overridden
* to allow matching.
*/
private static class IndirectEntry extends Entry {
private int tag;
private short index0;
private short index1;
/**
* Construct an IndirectEntry for a constant pool entry type
* that contains one index of another entry.
*/
public IndirectEntry(int tag, short index) {
this.tag = tag;
this.index0 = index;
this.index1 = 0;
}
/**
* Construct an IndirectEntry for a constant pool entry type
* that contains two indexes for other entries.
*/
public IndirectEntry(int tag, short index0, short index1) {
this.tag = tag;
this.index0 = index0;
this.index1 = index1;
}
public void write(DataOutputStream out) throws IOException {
out.writeByte(tag);
out.writeShort(index0);
/*
* If this entry type contains two indexes, write
* out the second, too.
*/
if (tag == CONSTANT_FIELD ||
tag == CONSTANT_METHOD ||
tag == CONSTANT_INTERFACEMETHOD ||
tag == CONSTANT_NAMEANDTYPE)
{
out.writeShort(index1);
}
}
public int hashCode() {
return tag + index0 + index1;
}
public boolean equals(Object obj) {
if (obj instanceof IndirectEntry) {
IndirectEntry other = (IndirectEntry) obj;
if (tag == other.tag &&
index0 == other.index0 && index1 == other.index1)
{
return true;
}
}
return false;
}
}
}
}
And this is the modified Proxy which I name ProxyEx:
// ProxyEx.java
package dynamicproxy.supportclass;
import java.lang.reflect.*;
public class ProxyEx {
public static Class<?> getProxyClass(ClassLoader loader, Class<?> superclass, Class<?>... interfaces) {
byte[] bytes = ProxyGeneratorEx.generateProxyClass(superclass.getSimpleName() + "$", superclass, interfaces);
return defineClass0(loader, "$Dog", bytes, 0, bytes.length);
}
/**
* TODO: no class cache support and no class name generation
*
* @param loader
* @param superclass
* @param interfaces
* @param h
* @return
*/
public static Object newProxyInstance(ClassLoader loader, Class<?> superclass, Class<?>[] interfaces, InvocationHandler h) {
Class<?> proxyClass = getProxyClass(loader, superclass, interfaces);
try {
Constructor constructor = proxyClass.getConstructor(InvocationHandler.class);
constructor.setAccessible(true);
return constructor.newInstance(h);
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
return null;
}
private static Class<?> defineClass0(ClassLoader loader, String name, byte[] b, int off, int len) {
Class proxyClass = Proxy.class;
try {
Method defineClass0Method = proxyClass.getDeclaredMethod("defineClass0", ClassLoader.class, String.class, byte[].class, int.class, int.class);
defineClass0Method.setAccessible(true);
return (Class<?>) defineClass0Method.invoke(null, loader, name, b, off, len);
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
return null;
}
}
Now let’s get a try with our dynamic proxy.
// Dog.java
package dynamicproxy.supportclass;
public class Dog {
public void bark(){}
}
// DogInvocationHandler.java
package dynamicproxy.supportclass;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
public class DogInvocationHandler implements InvocationHandler {
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
if("bark".equals(method.getName())) {
System.out.println("dog barked");
}
return null;
}
}
// Main.java
package dynamicproxy.supportclass;
public class Main {
public static void main(String[] args) {
System.getProperties().put("sun.misc.ProxyGeneratorEx.saveGeneratedFiles","true");
// Class aClass = ProxyEx.getProxyClass(A.class.getClassLoader(), A.class, new Class[]{});
Dog dog = (Dog) ProxyEx.newProxyInstance(Dog.class.getClassLoader(), Dog.class, new Class[0], new DogInvocationHandler());
dog.bark();
}
}
Here you should see the console will print “dog barked”.