Created
February 21, 2011 23:47
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package dyn; | |
import org.objectweb.asm.*; | |
import org.objectweb.asm.util.TraceClassVisitor; | |
import sun.dyn.anon.AnonymousClassLoader; | |
import java.io.PrintWriter; | |
public class Indy implements Opcodes { | |
public static void main(String[] args) { | |
MyCL myCL = new MyCL(); | |
Class caller = myCL.defineClass("Caller", makeCaller()); | |
try { | |
caller.getMethod("foo").invoke(caller.newInstance()); | |
} catch (Exception e) { | |
e.printStackTrace(); | |
} | |
} | |
public static class MyCL extends ClassLoader { | |
public Class defineClass(String name, byte[] code) { | |
return defineClass(name, code, 0, code.length); | |
} | |
} | |
public static byte[] makeCaller() { | |
ClassWriter cv = new ClassWriter(ClassWriter.COMPUTE_FRAMES); | |
TraceClassVisitor cw = new TraceClassVisitor(cv, new PrintWriter(System.out)); | |
MethodVisitor mv; | |
cw.visit(51, ACC_PUBLIC+ACC_SUPER, "Caller", null, "dyn/Invoker", null); | |
cw.visitField(ACC_PUBLIC, "callee", "Ljava/lang/Class;", null, null).visitEnd(); | |
{ | |
mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null); | |
mv.visitCode(); | |
mv.visitVarInsn(ALOAD, 0); | |
mv.visitMethodInsn(INVOKESPECIAL, "dyn/Invoker", "<init>", "()V"); | |
mv.visitVarInsn(ALOAD, 0); | |
mv.visitTypeInsn(NEW, "sun/dyn/anon/AnonymousClassLoader"); | |
mv.visitInsn(DUP); | |
mv.visitMethodInsn(INVOKESPECIAL, "sun/dyn/anon/AnonymousClassLoader", "<init>", "()V"); | |
mv.visitMethodInsn(INVOKESTATIC, "dyn/Indy", "makeCallee", "()[B"); | |
mv.visitMethodInsn(INVOKEVIRTUAL, "sun/dyn/anon/AnonymousClassLoader", "loadClass", "([B)Ljava/lang/Class;"); | |
mv.visitFieldInsn(PUTFIELD, "Caller", "callee", "Ljava/lang/Class;"); | |
mv.visitInsn(RETURN); | |
mv.visitMaxs(0, 0); | |
mv.visitEnd(); | |
} | |
{ | |
mv = cw.visitMethod(ACC_PUBLIC, "foo", "()V", null, null); | |
mv.visitCode(); | |
mv.visitVarInsn(ALOAD, 0); | |
mv.visitInsn(DUP); | |
mv.visitFieldInsn(GETFIELD, "Caller", "callee", "Ljava/lang/Class;"); | |
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Class", "newInstance", "()Ljava/lang/Object;"); | |
mv.visitFieldInsn(PUTFIELD, "Caller", "targetObject", "Ljava/lang/Object;"); | |
mv.visitLdcInsn("cde"); | |
mv.visitInvokeDynamicInsn("my:stuff", "(Ljava/lang/String;)V", | |
new MethodHandle(MH_INVOKEVIRTUAL, "Caller", "bootstrap", | |
new MethodType(Invoker.class.getMethods()[0]).getDescriptor())); | |
mv.visitInsn(RETURN); | |
mv.visitMaxs(0, 0); | |
mv.visitEnd(); | |
} | |
cw.visitEnd(); | |
return cv.toByteArray(); | |
} | |
public static byte[] makeCallee() { | |
ClassWriter cv = new ClassWriter(ClassWriter.COMPUTE_FRAMES); | |
TraceClassVisitor cw = new TraceClassVisitor(cv, new PrintWriter(System.out)); | |
MethodVisitor mv; | |
cw.visit(51, ACC_PUBLIC, "Callee", null, "java/lang/Object", null); | |
{ | |
mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null); | |
mv.visitCode(); | |
mv.visitVarInsn(ALOAD, 0); | |
mv.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V"); | |
mv.visitInsn(RETURN); | |
mv.visitMaxs(1, 1); | |
mv.visitEnd(); | |
} | |
{ | |
mv = cw.visitMethod(ACC_PUBLIC, "bar", "(Ljava/lang/String;)V", null, null); | |
mv.visitCode(); | |
mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;"); | |
mv.visitTypeInsn(NEW, "java/lang/StringBuilder"); | |
mv.visitInsn(DUP); | |
mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "()V"); | |
mv.visitLdcInsn("in bar "); | |
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;"); | |
mv.visitVarInsn(ALOAD, 1); | |
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;"); | |
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;"); | |
mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V"); | |
mv.visitInsn(RETURN); | |
mv.visitMaxs(0, 0); | |
mv.visitEnd(); | |
} | |
cw.visitEnd(); | |
return cv.toByteArray(); | |
} | |
} |
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package dyn; | |
import java.dyn.*; | |
public class Invoker { | |
protected Object targetObject; | |
public CallSite bootstrap(MethodHandles.Lookup lookup, String name, MethodType type) { | |
try { | |
MethodHandle handle = lookup.bind(targetObject, "bar", | |
MethodType.methodType(void.class, String.class)); | |
return new ConstantCallSite(handle); | |
} catch (NoAccessException e) { | |
throw new RuntimeException("Failed lookup", e); | |
} | |
} | |
} |
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