Java中是否有一种方法可以通过使用Instrumentation拦截对象的创建？

Question

我需要拦截所有ClassNotFoundException或NoClassDefError的创建：问题在于，其中的某些异常被某些库捕获，并重新抛出为其他异常类型，因此我无法检索类名。Java中是否可以通过使用Intstrumentation来做到这一点？

Answer 1

Answer 2

我不确定如何从我认为您需要的工具中调用回调。

ClassNotFoundException

这需要使用META-INF / MANIFEST.MF像这样编译成JAR文件

System.err.println

并使用程序参数

import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.lang.instrument.Instrumentation;
import java.lang.instrument.UnmodifiableClassException;
import java.security.ProtectionDomain;

import net.bytebuddy.jar.asm.ClassReader;
import net.bytebuddy.jar.asm.ClassVisitor;
import net.bytebuddy.jar.asm.ClassWriter;
import net.bytebuddy.jar.asm.MethodVisitor;
import net.bytebuddy.jar.asm.Opcodes;

public class ClassNotFoundExceptionIntercept {

    public static void premain(String agentArgs, Instrumentation inst) throws UnmodifiableClassException {
        inst.addTransformer(new ClassFileTransformer() {
            @Override
            public byte[] transform(ClassLoader l, String name, Class<?> c, ProtectionDomain d, byte[] b)
                    throws IllegalClassFormatException {
                if ("java/lang/ClassNotFoundException".equals(name)) {
                    return instrument(b);
                }
                return b;
            }
        }, true);
        inst.retransformClasses(java.lang.ClassNotFoundException.class);
    }

    private static byte[] instrument(byte[] originalBytes) {
        ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES);
        ClassAdapter adapter = new ClassAdapter(cw);
        ClassReader cr = new ClassReader(originalBytes);
        cr.accept(adapter, ClassReader.SKIP_FRAMES);
        return cw.toByteArray();
    }

    public static class ClassAdapter extends ClassVisitor implements Opcodes {
        public ClassAdapter(ClassVisitor cv) {
            super(ASM4, cv);
        }
        @Override
        public MethodVisitor visitMethod(int access, String name, String descriptor, String signature,
                String[] exceptions) {
            if ("<init>".equals(name)) {
                MethodVisitor mv = cv.visitMethod(access, name, descriptor, signature, exceptions);
                return new Wrapper(mv);
            } else {
                return super.visitMethod(access, name, descriptor, signature, exceptions);
            }
        }
    }

    private static class Wrapper extends MethodVisitor {
        public Wrapper(MethodVisitor mv) {
            super(Opcodes.ASM4, mv);
        }
        @Override
        public void visitMethodInsn(int opcode, String owner, String name, String desc, boolean itf) {
            mv.visitMethodInsn(opcode, owner, name, desc, itf);

            mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/System", "err", "Ljava/io/PrintStream;");
            mv.visitLdcInsn("Constructor invoked");
            mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);
        }
    }

}

调用

这可以证明与吞噬异常的测试类一起使用
Manifest-Version: 1.0
Premain-Class: ClassNotFoundExceptionIntercept
Agent-Class: ClassNotFoundExceptionIntercept
Can-Retransform-Classes: true
Can-Redefine-Classes: true

输出

-javaagent:/home/adam/agent-example.jar