Android ASM字节码插桩（下）

由于内容篇幅限制，紧接着上篇
https://www.jianshu.com/p/c975081b43fd?u_atoken=de4d112a-6864-4703-ad69-f82922d505de&u_asession=01X_C9UMmFccLMXpIfjRM8FYXsq1g_CrgffyPiHHUpgZGBrWiw193wtdhvbyaJ4chEX0KNBwm7Lovlpxjd_P_q4JsKWYrT3W_NKPr8w6oU7K_OI3-HIFVcmZbMNunYRvYCslvTX-jMTLEIhdGFg3rxgWBkFo3NEHBv0PZUm6pbxQU&u_asig=05e9XZPq2Q7yJkKdk86YtiyFfiNPAdPSg-Voed-oPaPvY2QwBnCAT6a9bvIxBzozUzQDvsYuznxmEgCniYpEFR8BE5VfTwKn3vCIpIwgp7gRXcA22dI9OX-SjB0FJAYc2ww3dPL_NNCbygKg7jU_P9L1CtmgFQaXXOFbG5UybdQYj9JS7q8ZD7Xtz2Ly-b0kmuyAKRFSVJkkdwVUnyHAIJzet9GpoGT6ubHEJ3SNQzl3mpaIfenFB8MFcEbsDwJo4a6FPw117USKdEPc8n7HkzU-3h9VXwMyh6PgyDIVSG1W-IddwkY7v-CAh1IBL0sYO20tCNasH120WVmgCT0pzm_wUd5n3s6RPzq9rJ9ybbMWH4abeDNZysnYRhxU5ybSOYmWspDxyAEEo4kbsryBKb9Q&u_aref=%2FnUp0P8E0Oe%2BxeO5Bz5i0j215Eo%3D

3.6 执行InjectUnitTest.java的test()方法查看InjectTest.class结果

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package com.xyaty.asmdemo;

public class InjectTest {
    public InjectTest() {
        long var1 = System.currentTimeMillis();
        long var3 = System.currentTimeMillis();
        System.out.println("execute: " + (var3 - var1) + "ms");
    }

    public static void main(String[] var0) throws InterruptedException {
        long var1 = System.currentTimeMillis();
        Thread.sleep(1000L);
        long var3 = System.currentTimeMillis();
        System.out.println("execute: " + (var3 - var1) + "ms");
    }

    public void methodA() {
        long var1 = System.currentTimeMillis();
        System.out.println("methodA");
        long var3 = System.currentTimeMillis();
        System.out.println("execute: " + (var3 - var1) + "ms");
    }
}

发现在每个方法中都加入了

long var1 = System.currentTimeMillis();
和
long var3 = System.currentTimeMillis();
System.out.println("execute: " + (var3 - var1) + "ms");

如果仅仅在main()方法才注入代码，就需要引入自定义注解来标记指定的方法

四、引入自定义注解，标记方法才注入代码
4.1 注解类ASMTest.java，并通过javac编译成ASMTest.class（略）

package com.xyaty.asmdemo;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * DESC   :
 */
@Retention(RetentionPolicy.CLASS)
@Target(ElementType.METHOD)
public @interface ASMTest {

}

4.2 在InjectTest.java的main()方法上加上注解@ASMTest，标记此方法，并通过javac生成class

package com.xyaty.asmdemo;

/**
 * DESC   :
 */
public class InjectTest {

    @ASMTest
    public static void main(String[] args) throws InterruptedException {
        Thread.sleep(1000);
    }

    public void methodA() {
        System.out.println("methodA");
    }
}

4.3 在上述MyMethodVisitor的下列方法中加入注解判断

        @Override
        public AnnotationVisitor visitAnnotation(String descriptor, boolean visible) {
            System.out.println("visitAnnotation===>methodName="+getName()+", descriptor="+descriptor);
            //如果方法的注解名字是@ASMTest，则给此方法注入代码
            if ("Lcom/xyaty/asmdemo/ASMTest;".equals(descriptor)) {
                isInject = true;
            } else {
                isInject = false;
            }
            return super.visitAnnotation(descriptor, visible);
        }

        /**
         * 进入方法插入内容
         */
        @Override
        protected void onMethodEnter() {
            super.onMethodEnter();

            if (!isInject) {
                return;
            }
        }

@Override
        protected void onMethodExit(int opcode) {
            super.onMethodExit(opcode);

            if (!isInject) {
                return;
            }
}

InjectUnitTest.java完整代码如下：

package com.xyaty.asmdemo;

import org.junit.Test;
import org.objectweb.asm.AnnotationVisitor;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;
import org.objectweb.asm.commons.AdviceAdapter;
import org.objectweb.asm.commons.Method;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;

/**
 * DESC   :
 */
public class InjectUnitTest {
    /**
     * 单元测试方法，右击test()方法，选择run test()方法即可查看结果
     */
    @Test
    public void test() {
        try {
            //读取待插桩的class
            FileInputStream fis = new FileInputStream(
                    new File("src/test/java/com/xyaty/asmdemo/InjectTest.class"));

            /**
             * 执行分析与插桩
             * ClassReader是class字节码的读取与分析引擎
             */
            ClassReader classReader = new ClassReader(fis);
            // ClassWriter写出器， COMPUTE_FRAMES表示自动计算栈帧和局部变量表的大小
            ClassWriter classWriter = new ClassWriter(ClassWriter.COMPUTE_FRAMES);
            /**
             * 执行分析，处理结果写入classWriter， EXPAND_FRAMES表示栈图以扩展格式进行访问
             * 执行插桩的代码就在MyClassVisitor中实现
             */
            classReader.accept(new MyClassVisitor(Opcodes.ASM9, classWriter), ClassReader.EXPAND_FRAMES);

            //获得执行了插桩之后的字节码数据
            byte[] bytes = classWriter.toByteArray();
            // 重新写入InjectTest.class中（也可以写入到其他class中，InjectTest1.class），完成插桩
            FileOutputStream fos = new FileOutputStream(
                    new File("src/test/java/com/xyaty/asmdemo/InjectTest.class"));
            fos.write(bytes);
            fos.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public class MyClassVisitor extends ClassVisitor {

        public MyClassVisitor(int api, ClassVisitor classVisitor) {
            super(api, classVisitor);
        }

        @Override
        public MethodVisitor visitMethod(int access, String name, String descriptor, String signature, String[] exceptions) {
            System.out.println("visitMethod==>name="+name);
            /**
             * 会输出以下方法：
             * visitMethod==>name=
             * visitMethod==>name=main
             */
            MethodVisitor methodVisitor = super.visitMethod(access, name, descriptor, signature, exceptions);
            return new MyMethodVisitor(api, methodVisitor, access, name,descriptor);
        }
    }


    /**
     * 之所以继承自AdviceAdapter，是因为AdviceAdapter是MethodVisitor的子类，
     * AdviceAdapter封装了指令插入方法，更为直观与简单，
     * 要使用其中的onMethodEnter和 onMethodExit方法进行字节码插桩，
     *
     * 继承关系如下：
     * AdviceAdapter extends GeneratorAdapter
     * GeneratorAdapter extends LocalVariablesSorter
     * LocalVariablesSorter extends MethodVisitor
     */
    public class MyMethodVisitor extends AdviceAdapter {
        long start;
        private int startIdentifier;
        private boolean isInject = false;//是否注入代码

        @Override
        public AnnotationVisitor visitAnnotation(String descriptor, boolean visible) {
            System.out.println("visitAnnotation===>methodName="+getName()+", descriptor="+descriptor);
            //如果方法的注解名字是@ASMTest，则给此方法注入代码
            if ("Lcom/xyaty/asmdemo/ASMTest;".equals(descriptor)) {
                isInject = true;
            } else {
                isInject = false;
            }
            return super.visitAnnotation(descriptor, visible);
        }

        protected MyMethodVisitor(int api, MethodVisitor methodVisitor, int access, String name, String descriptor) {
            super(api, methodVisitor, access, name, descriptor);
        }

        /**
         * 进入方法插入内容
         */
        @Override
        protected void onMethodEnter() {
            super.onMethodEnter();

            if (!isInject) {
                return;
            }

//            start = System.currentTimeMillis();
            /**
             * @Type owner 调用哪个类
             * @Method method 调用某个类的静态方法（参数name: 方法名字，descriptor：方法中参数和方法返回值类型）
             */
            invokeStatic(Type.getType("Ljava/lang/System;"), new Method("currentTimeMillis", "()J"));
            //调用newLocal创建一个long类型的变量，返回一个int类型索引identifier
            startIdentifier = newLocal(Type.LONG_TYPE);
            //保存到本地变量索引中，用一个本地变量接收上一步执行的结果
            storeLocal(startIdentifier);
        }

        /**
         * 在方法结尾插入内容
         * @param opcode
         */
        @Override
        protected void onMethodExit(int opcode) {
            super.onMethodExit(opcode);

            if (!isInject) {
                return;
            }

//            long end = System.currentTimeMillis();
//            System.out.println("execute: "+(end - start)+"ms");

            invokeStatic(Type.getType("Ljava/lang/System;"), new Method("currentTimeMillis", "()J"));
            //调用newLocal创建一个long类型的变量，返回一个int类型索引identifier
            int endIdentifier = newLocal(Type.LONG_TYPE);
            //保存到本地变量索引中，用一个本地变量接收上一步执行的结果
            storeLocal(endIdentifier);

            //获取System的静态字段out,类型为PrintStream
            getStatic(Type.getType("Ljava/lang/System;"),
                    "out", Type.getType("Ljava/io/PrintStream;"));

            /**
             * "execute: "+(end - start)+"ms"实际是内部创建StringBuilder来拼接
             * 源码：NEW java/lang/StringBuilder
             * 创建一个对象StringBuilder
             */
            newInstance(Type.getType("Ljava/lang/StringBuilder;"));
            // dup压入栈顶，让下面的INVOKESPECIAL 知道执行谁的构造方法创建StringBuilder
            dup();
            /**
             * 源码：INVOKESPECIAL java/lang/StringBuilder. ()V
             * 创建StringBuilder的构造方法，用init来代替
             */
            invokeConstructor(Type.getType("Ljava/lang/StringBuilder;"),
                    new Method("", "()V"));

            visitLdcInsn("execute: ");
            /**
             * 源码：INVOKEVIRTUAL java/lang/StringBuilder.append (Ljava/lang/String;)Ljava/lang/StringBuilder;
             * 调用append方法
             */
            invokeVirtual(Type.getType("Ljava/lang/StringBuilder;"),
                    new Method("append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;"));
            /**
             * 对结束时间和开始时间进行减法操作
             * LLOAD 3 先加载结束时间
             * LLOAD 1 后加载开始时间
             * LSUB    执行减法操作
             */
            loadLocal(endIdentifier);
            loadLocal(startIdentifier);
            //执行减法操作，返回long类型
            math(SUB, Type.LONG_TYPE);

            /**
             * 源码：INVOKEVIRTUAL java/lang/StringBuilder.append (J)Ljava/lang/StringBuilder;
             * LDC "ms"
             */
            invokeVirtual(Type.getType("Ljava/lang/StringBuilder;"),
                    new Method("append", "(J)Ljava/lang/StringBuilder;"));
            //拼接毫秒
            visitLdcInsn("ms");

            /**
             * 源码：
             * INVOKEVIRTUAL java/lang/StringBuilder.append (Ljava/lang/String;)Ljava/lang/StringBuilder;
             * INVOKEVIRTUAL java/lang/StringBuilder.toString ()Ljava/lang/String;
             * INVOKEVIRTUAL java/io/PrintStream.println (Ljava/lang/String;)V
             */
            invokeVirtual(Type.getType("Ljava/lang/StringBuilder;"),
                    new Method("append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;"));
            invokeVirtual(Type.getType("Ljava/lang/StringBuilder;"),
                    new Method("toString", "()Ljava/lang/String;"));
            invokeVirtual(Type.getType("Ljava/io/PrintStream;"),
                    new Method("println", "(Ljava/lang/String;)V"));
        }

    }
}

再次运行InjectTest.class结果如下，可以看到只有main()方法注入了代码

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package com.xyaty.asmdemo;

public class InjectTest {
    public InjectTest() {
    }

    @ASMTest
    public static void main(String[] var0) throws InterruptedException {
        long var1 = System.currentTimeMillis();
        Thread.sleep(1000L);
        long var3 = System.currentTimeMillis();
        System.out.println("execute: " + (var3 - var1) + "ms");
    }

    public void methodA() {
        System.out.println("methodA");
    }
}

到此结束。

参考文章：
https://blog.csdn.net/zenmela2011/article/details/125586333
https://blog.csdn.net/huangbin123/article/details/123322667

Android ASM字节码插桩（下）

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