Java agent+ASM实战--监控所有方法执行时间

本文建立在对instrumentation和agent有初步的了解的前提下阅读，关于这2个类的讲解在其它文章中。

这是一个maven项目，pom中需要的配置，lib中有asm的jar包

 
                    maven-compiler-plugin
                    3.7.0
                    
                        1.8
                        1.8
                        
                            lib
                        
                    
                
                
                    maven-jar-plugin
                    3.0.2
                    
                        
                            
                                true
                            
                            
                                com.runtime.bytecode.UdAgent
                            

                        
                    
                

打包后的agent的jar包中manifest属性如下：

Manifest-Version: 1.0
Premain-Class: com.runtime.bytecode.UdAgent
Built-By: lenovo
Created-By: Apache Maven 3.3.9
Build-Jdk: 1.8.0_121

agent类，只有一个方法，就是把自定义的类修改器添加到instrumentation中。

public class UdAgent {
    public static void premain(String agentArgs, Instrumentation instrumentation){
        instrumentation.addTransformer(new LogTransformer());
    }
}

类转换器实现：

package com.runtime.bytecode.transformer;

import com.runtime.bytecode.adapter.TimeCountAdpter;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;

import java.io.IOException;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.security.ProtectionDomain;

public class LogTransformer  implements ClassFileTransformer{
    @Override
    public byte[] transform(ClassLoader loader, String className, Class classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {
        try {
            ClassReader cr= new ClassReader(className);
            ClassWriter cw=new ClassWriter(ClassWriter.COMPUTE_MAXS);
            TimeCountAdpter timeCountAdpter=new TimeCountAdpter(cw);

            cr.accept(timeCountAdpter,ClassReader.EXPAND_FRAMES);

            return cw.toByteArray();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
}

实际修改字节码的方法，这里给每个类添加了一个字段UDASMCN，用于记录当前类的名字（方便打印信息）。同时记录每个方法的名字，以及执行时间。

package com.runtime.bytecode.adapter;

import org.objectweb.asm.*;
import org.objectweb.asm.commons.AnalyzerAdapter;
import org.objectweb.asm.commons.LocalVariablesSorter;

import javax.xml.ws.soap.MTOM;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;

public class TimeCountAdpter extends ClassVisitor implements Opcodes {
    private String owner;
    private boolean isInterface;
    private String filedName="UDASMCN";
    private int acc=Opcodes.ACC_PUBLIC+Opcodes.ACC_STATIC+Opcodes.ACC_FINAL;
    private boolean isPresent=false;

    private String methodName;

    public TimeCountAdpter(ClassVisitor classVisitor) {
        super(ASM6, classVisitor);
    }

    @Override
    public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {
        super.visit(version, access, name, signature, superName, interfaces);
        owner = name;
        isInterface = (access & ACC_INTERFACE) != 0;
    }
    @Override
    public FieldVisitor visitField(int access, String name, String descriptor, String signature, Object value) {
        if (name.equals(filedName)){
            isPresent=true;
        }
        return super.visitField(access, name, descriptor, signature, value);
    }
    @Override
    public MethodVisitor visitMethod(int access, String name, String descriptor, String signature, String[] exceptions) {
        MethodVisitor mv=cv.visitMethod(access, name, descriptor, signature, exceptions);

        if (!isInterface && mv != null && !name.equals("") && !name.equals("")) {
            methodName=name;
            AddTimerMethodAdapter at = new AddTimerMethodAdapter(mv);
            at.aa = new AnalyzerAdapter(owner, access, name, descriptor, at);
            at.lvs = new LocalVariablesSorter(access, descriptor, at.aa);

            return at.lvs;
        }

        return mv;
    }

    public void visitEnd() {
        if (!isInterface) {
            FieldVisitor fv = cv.visitField(acc, filedName,
                    "Ljava/lang/String;", null, owner);
            if (fv != null) {
                fv.visitEnd();
            }
        }
        cv.visitEnd();
    }

    class AddTimerMethodAdapter extends MethodVisitor {
        private int time;
        private int maxStack;
        public LocalVariablesSorter lvs;
        public AnalyzerAdapter aa;

        public AddTimerMethodAdapter(MethodVisitor methodVisitor) {
            super(ASM6, methodVisitor);
        }


        @Override
        public void visitCode() {
            mv.visitCode();
            mv.visitMethodInsn(INVOKESTATIC, "java/lang/System", "nanoTime", "()J", false);
            time=lvs.newLocal(Type.LONG_TYPE);
            mv.visitVarInsn(LSTORE, time);
            maxStack=4;
        }

        @Override
        public void visitInsn(int opcode) {
            if (((opcode >= IRETURN && opcode <= RETURN) || opcode == ATHROW) && !isPresent) {
                mv.visitMethodInsn(INVOKESTATIC, "java/lang/System", "nanoTime", "()J", false);
                mv.visitVarInsn(LLOAD, time);
                mv.visitInsn(LSUB);
                mv.visitVarInsn(LSTORE, time);

                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", "", "()V", false);
                mv.visitFieldInsn(GETSTATIC, owner, filedName, "Ljava/lang/String;");
                mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;", false);

                mv.visitLdcInsn("  "+methodName+":");
                mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;", false);

                mv.visitVarInsn(LLOAD, time);
                mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(J)Ljava/lang/StringBuilder;", false);
                mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;", false);
                mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);

                maxStack=Math.max(aa.stack.size()+4,maxStack);
            }
            mv.visitInsn(opcode);
        }

        @Override
        public void visitMaxs(int maxStack, int maxLocals) {
            super.visitMaxs(Math.max(maxStack,this.maxStack), maxLocals);
        }
    }

}

打包成jar包后，在另一个程序启动时调用，启动参数如下：

 -javaagent:D:\项目\bytecode\target\bytecode-1.0-SNAPSHOT.jar

执行效果：
时间单位是纳秒，可以看到每个方法执行完时，都会打印这个方法 的执行时间，以com/Main main:11457636为例，说明类com/Main的main方法执行力11毫秒。

java/util/concurrent/locks/AbstractQueuedSynchronizer  doReleaseShared:821
java/util/concurrent/locks/AbstractQueuedSynchronizer  releaseShared:55384
java/util/concurrent/CountDownLatch  countDown:63590
main do else something
main 执行结束
com/Main  main:11457636

agent原理