CGLIB动态代理--实例/原理

简介

说明

本文用示例介绍CGLIB动态代理的用法。

原理

        CGLIB是针对类来实现代理的。

        原理是对指定的目标类生成一个子类，并覆盖其中方法实现增强，但因为采用的是继承，所以不能对final修饰的类进行代理。 

限制

        JDK的动态代理机制只能代理实现了接口的类，而不能实现接口的类就不能实现JDK的动态代理。

实例：统计执行时间

依赖

<dependency>
            <groupId>cglib</groupId>
            <artifactId>cglib</artifactId>
            <version>3.2.5</version>
        </dependency>

 较低版本的cglib可能需要此依赖：

<dependency>
    <groupId>org.ow2.asm</groupId>
    <artifactId>asm</artifactId>
    <version>5.0.1</version>
</dependency>

代码

package org.example.a;

import net.sf.cglib.core.DebuggingClassWriter;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;

import java.lang.reflect.Method;

//被代理类
class ExecutionTimeReality {
    //这里打印出任务名，并休眠500ms模拟任务执行了很长时间
    public void dealTask(String taskName) {
        System.out.println("Task is running: " + taskName);
        try {
            Thread.sleep(500);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    //这里打印出任务名，并休眠500ms模拟任务执行了很长时间
    public void sayHello(String name) {
        System.out.println("hello: " + name);
    }
}

//代理类
class ExecutionTimeProxy implements MethodInterceptor {

    @Override
    public Object intercept(Object obj, Method method, Object[] args,
                            MethodProxy proxy) throws Throwable {
        long startTime = System.currentTimeMillis();
        proxy.invokeSuper(obj, args);
        long endTime = System.currentTimeMillis();
        System.out.println("Elapsed time: " + (endTime - startTime) + " ms");

        return null;
    }
}

//工厂方法获得代理对象
class DynamicProxyFactory {
    public static Object getInstance() {
        Object target = new ExecutionTimeReality();
        ExecutionTimeProxy proxySubject = new ExecutionTimeProxy();
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(target.getClass());
        enhancer.setCallback(proxySubject);
        return enhancer.create();
    }
}

public class Demo {
    public static void main(String[] args) {
        System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "E:\\CglibProxyClass");
        ExecutionTimeReality subject = (ExecutionTimeReality) DynamicProxyFactory.getInstance();
        subject.dealTask("TestTask");
    }
}

执行结果

Task is running: TestTask
Elapsed time: 524 ms

原理

流程概述

本部分应该放到最后作为结论。但本处为了快速体会总体流程，放到最前边。

实例化Enhancer并设置要代理的类及回调（MethodInterceptor接口的实现类对象）

创建代理类（继承自被代理类）

被代理类的dealTask方法（已被代理类覆写，实际调用代理类的dealTask方法）

    回调的intercept方法（ExecutionTimeProxy.intercept）  //回调是在第一步中传进来的

        proxy.invokeSuper(obj, args);                //调用父类  invokeSuper方法是MethodProxy声明的

            this.init();            //若不存在FastClass，则生成

                this.fastClassInfo.f2.invoke(fci.i2, obj, args);

                    FastClass的invoke方法

                        将第一个参数与数字比对，执行对应的方法  

手动生成代理类源码

分析源码，就要看生成的代理类源码，生成方法：在main最开始写此代码：

System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "E:\\CglibProxyClass");

运行后，会生成E:/CglibProxyClass文件夹，其结构如下

E:\CGLIBPROXYCLASS
├─net
│  └─sf
│      └─cglib
│          ├─core
│          │      MethodWrapper$MethodWrapperKey$$KeyFactoryByCGLIB$$d45e49f7.class
│          │
│          └─proxy
│                  Enhancer$EnhancerKey$$KeyFactoryByCGLIB$$7fb24d72.class
│
└─org
    └─example
        └─a
                ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386$$FastClassByCGLIB$$bebee033.class
                ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386.class
                ExecutionTimeReality$$FastClassByCGLIB$$81389d66.class

因为两个$显示不正常，所以下边用一个$表示两个$

ExecutionTimeReality$EnhancerByCGLIB$5a92c386$FastClassByCGLIB$bebee033.class

快速类1。此类暂不讨论。代码中没分析到。

ExecutionTimeReality$EnhancerByCGLIB$5a92c386.class

代理类，会调用到ExecutionTimeReality$EnhancerByCGLIB$5a92c386.class

ExecutionTimeReality$FastClassByCGLIB$81389d66.class

快速类2。被代理类调用到。FastClass并不是跟代理类一块生成的，而是在第一次执行MethodProxy invoke/invokeSuper时生成的并放在了缓存中。

ExecutionTimeReality$EnhancerByCGLIB$5a92c386.class

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

package org.example.a;

import java.lang.reflect.Method;
import net.sf.cglib.core.ReflectUtils;
import net.sf.cglib.core.Signature;
import net.sf.cglib.proxy.Callback;
import net.sf.cglib.proxy.Factory;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;

public class ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386 extends ExecutionTimeReality implements Factory {
    private boolean CGLIB$BOUND;
    public static Object CGLIB$FACTORY_DATA;
    private static final ThreadLocal CGLIB$THREAD_CALLBACKS;
    private static final Callback[] CGLIB$STATIC_CALLBACKS;
    private MethodInterceptor CGLIB$CALLBACK_0;
    private static Object CGLIB$CALLBACK_FILTER;
    private static final Method CGLIB$dealTask$0$Method;
    private static final MethodProxy CGLIB$dealTask$0$Proxy;
    private static final Object[] CGLIB$emptyArgs;
    private static final Method CGLIB$sayHello$1$Method;
    private static final MethodProxy CGLIB$sayHello$1$Proxy;
    private static final Method CGLIB$equals$2$Method;
    private static final MethodProxy CGLIB$equals$2$Proxy;
    private static final Method CGLIB$toString$3$Method;
    private static final MethodProxy CGLIB$toString$3$Proxy;
    private static final Method CGLIB$hashCode$4$Method;
    private static final MethodProxy CGLIB$hashCode$4$Proxy;
    private static final Method CGLIB$clone$5$Method;
    private static final MethodProxy CGLIB$clone$5$Proxy;

    static void CGLIB$STATICHOOK1() {
        CGLIB$THREAD_CALLBACKS = new ThreadLocal();
        CGLIB$emptyArgs = new Object[0];
        Class var0 = Class.forName("org.example.a.ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386");
        Class var1;
        Method[] var10000 = ReflectUtils.findMethods(new String[]{"equals", "(Ljava/lang/Object;)Z", "toString", "()Ljava/lang/String;", "hashCode", "()I", "clone", "()Ljava/lang/Object;"}, (var1 = Class.forName("java.lang.Object")).getDeclaredMethods());
        CGLIB$equals$2$Method = var10000[0];
        CGLIB$equals$2$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/Object;)Z", "equals", "CGLIB$equals$2");
        CGLIB$toString$3$Method = var10000[1];
        CGLIB$toString$3$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/String;", "toString", "CGLIB$toString$3");
        CGLIB$hashCode$4$Method = var10000[2];
        CGLIB$hashCode$4$Proxy = MethodProxy.create(var1, var0, "()I", "hashCode", "CGLIB$hashCode$4");
        CGLIB$clone$5$Method = var10000[3];
        CGLIB$clone$5$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/Object;", "clone", "CGLIB$clone$5");
        var10000 = ReflectUtils.findMethods(new String[]{"dealTask", "(Ljava/lang/String;)V", "sayHello", "(Ljava/lang/String;)V"}, (var1 = Class.forName("org.example.a.ExecutionTimeReality")).getDeclaredMethods());
        CGLIB$dealTask$0$Method = var10000[0];
        CGLIB$dealTask$0$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/String;)V", "dealTask", "CGLIB$dealTask$0");
        CGLIB$sayHello$1$Method = var10000[1];
        CGLIB$sayHello$1$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/String;)V", "sayHello", "CGLIB$sayHello$1");
    }

    final void CGLIB$dealTask$0(String var1) {
        super.dealTask(var1);
    }

    public final void dealTask(String var1) {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            var10000.intercept(this, CGLIB$dealTask$0$Method, new Object[]{var1}, CGLIB$dealTask$0$Proxy);
        } else {
            super.dealTask(var1);
        }
    }

    final void CGLIB$sayHello$1(String var1) {
        super.sayHello(var1);
    }

    public final void sayHello(String var1) {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            var10000.intercept(this, CGLIB$sayHello$1$Method, new Object[]{var1}, CGLIB$sayHello$1$Proxy);
        } else {
            super.sayHello(var1);
        }
    }

    final boolean CGLIB$equals$2(Object var1) {
        return super.equals(var1);
    }

    public final boolean equals(Object var1) {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            Object var2 = var10000.intercept(this, CGLIB$equals$2$Method, new Object[]{var1}, CGLIB$equals$2$Proxy);
            return var2 == null ? false : (Boolean)var2;
        } else {
            return super.equals(var1);
        }
    }

    final String CGLIB$toString$3() {
        return super.toString();
    }

    public final String toString() {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        return var10000 != null ? (String)var10000.intercept(this, CGLIB$toString$3$Method, CGLIB$emptyArgs, CGLIB$toString$3$Proxy) : super.toString();
    }

    final int CGLIB$hashCode$4() {
        return super.hashCode();
    }

    public final int hashCode() {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            Object var1 = var10000.intercept(this, CGLIB$hashCode$4$Method, CGLIB$emptyArgs, CGLIB$hashCode$4$Proxy);
            return var1 == null ? 0 : ((Number)var1).intValue();
        } else {
            return super.hashCode();
        }
    }

    final Object CGLIB$clone$5() throws CloneNotSupportedException {
        return super.clone();
    }

    protected final Object clone() throws CloneNotSupportedException {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        return var10000 != null ? var10000.intercept(this, CGLIB$clone$5$Method, CGLIB$emptyArgs, CGLIB$clone$5$Proxy) : super.clone();
    }

    public static MethodProxy CGLIB$findMethodProxy(Signature var0) {
        String var10000 = var0.toString();
        switch(var10000.hashCode()) {
        case -1165719922:
            if (var10000.equals("dealTask(Ljava/lang/String;)V")) {
                return CGLIB$dealTask$0$Proxy;
            }
            break;
        case -508378822:
            if (var10000.equals("clone()Ljava/lang/Object;")) {
                return CGLIB$clone$5$Proxy;
            }
            break;
        case 771401912:
            if (var10000.equals("sayHello(Ljava/lang/String;)V")) {
                return CGLIB$sayHello$1$Proxy;
            }
            break;
        case 1826985398:
            if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
                return CGLIB$equals$2$Proxy;
            }
            break;
        case 1913648695:
            if (var10000.equals("toString()Ljava/lang/String;")) {
                return CGLIB$toString$3$Proxy;
            }
            break;
        case 1984935277:
            if (var10000.equals("hashCode()I")) {
                return CGLIB$hashCode$4$Proxy;
            }
        }

        return null;
    }

    public ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386() {
        CGLIB$BIND_CALLBACKS(this);
    }

    public static void CGLIB$SET_THREAD_CALLBACKS(Callback[] var0) {
        CGLIB$THREAD_CALLBACKS.set(var0);
    }

    public static void CGLIB$SET_STATIC_CALLBACKS(Callback[] var0) {
        CGLIB$STATIC_CALLBACKS = var0;
    }

    private static final void CGLIB$BIND_CALLBACKS(Object var0) {
        ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386 var1 = (ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386)var0;
        if (!var1.CGLIB$BOUND) {
            var1.CGLIB$BOUND = true;
            Object var10000 = CGLIB$THREAD_CALLBACKS.get();
            if (var10000 == null) {
                var10000 = CGLIB$STATIC_CALLBACKS;
                if (var10000 == null) {
                    return;
                }
            }

            var1.CGLIB$CALLBACK_0 = (MethodInterceptor)((Callback[])var10000)[0];
        }

    }

    public Object newInstance(Callback[] var1) {
        CGLIB$SET_THREAD_CALLBACKS(var1);
        ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386 var10000 = new ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386();
        CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
        return var10000;
    }

    public Object newInstance(Callback var1) {
        CGLIB$SET_THREAD_CALLBACKS(new Callback[]{var1});
        ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386 var10000 = new ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386();
        CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
        return var10000;
    }

    public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) {
        CGLIB$SET_THREAD_CALLBACKS(var3);
        ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386 var10000 = new ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386;
        switch(var1.length) {
        case 0:
            var10000.<init>();
            CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
            return var10000;
        default:
            throw new IllegalArgumentException("Constructor not found");
        }
    }

    public Callback getCallback(int var1) {
        CGLIB$BIND_CALLBACKS(this);
        MethodInterceptor var10000;
        switch(var1) {
        case 0:
            var10000 = this.CGLIB$CALLBACK_0;
            break;
        default:
            var10000 = null;
        }

        return var10000;
    }

    public void setCallback(int var1, Callback var2) {
        switch(var1) {
        case 0:
            this.CGLIB$CALLBACK_0 = (MethodInterceptor)var2;
        default:
        }
    }

    public Callback[] getCallbacks() {
        CGLIB$BIND_CALLBACKS(this);
        return new Callback[]{this.CGLIB$CALLBACK_0};
    }

    public void setCallbacks(Callback[] var1) {
        this.CGLIB$CALLBACK_0 = (MethodInterceptor)var1[0];
    }

    static {
        CGLIB$STATICHOOK1();
    }
}

        通过代理类的源码可以看到，代理类会获得所有在父类继承来的方法，并且会有MethodProxy与之对应，比如：

private static final Method CGLIB$dealTask$0$Method;
private static final MethodProxy CGLIB$dealTask$0$Proxy;
private static final Method CGLIB$sayHello$1$Method;
private static final MethodProxy CGLIB$sayHello$1$Proxy;

        另外，从代理类的类型来看，它直接继承要代理的类，所以可以代理的没有接口的类。其实，它跟接口没关系了，有接口也不会用到。

public class ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386 extends ExecutionTimeReality implements Factory

方法的调用

final void CGLIB$dealTask$0(String var1) {
    super.dealTask(var1);
}

public final void dealTask(String var1) {
    MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
    if (var10000 == null) {
        CGLIB$BIND_CALLBACKS(this);
        var10000 = this.CGLIB$CALLBACK_0;
    }

    if (var10000 != null) {
        var10000.intercept(this, CGLIB$dealTask$0$Method, new Object[]{var1}, CGLIB$dealTask$0$Proxy);
    } else {
        super.dealTask(var1);
    }
}

FastClass机制

        Cglib动态代理执行代理方法效率之所以比JDK的高是因为Cglib采用了FastClass机制，它的原理简单来说就是：为代理类和被代理类各生成一个Class，这个Class会为代理类或被代理类的方法分配一个index(int类型)。这个index当做一个入参，FastClass就可以直接定位要调用的方法直接进行调用，这样省去了反射调用，所以调用效率比JDK动态代理通过反射调用高。

ExecutionTimeReality$FastClassByCGLIB$81389d66

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

package org.example.a;

import java.lang.reflect.InvocationTargetException;
import net.sf.cglib.core.Signature;
import net.sf.cglib.reflect.FastClass;

public class ExecutionTimeReality$$FastClassByCGLIB$$81389d66 extends FastClass {
    public ExecutionTimeReality$$FastClassByCGLIB$$81389d66(Class var1) {
        super(var1);
    }

    public int getIndex(Signature var1) {
        String var10000 = var1.toString();
        switch(var10000.hashCode()) {
        case -1165719922:
            if (var10000.equals("dealTask(Ljava/lang/String;)V")) {
                return 0;
            }
            break;
        case 771401912:
            if (var10000.equals("sayHello(Ljava/lang/String;)V")) {
                return 1;
            }
            break;
        case 1826985398:
            if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
                return 2;
            }
            break;
        case 1913648695:
            if (var10000.equals("toString()Ljava/lang/String;")) {
                return 3;
            }
            break;
        case 1984935277:
            if (var10000.equals("hashCode()I")) {
                return 4;
            }
        }

        return -1;
    }

    public int getIndex(String var1, Class[] var2) {
        switch(var1.hashCode()) {
        case -2012993625:
            if (var1.equals("sayHello")) {
                switch(var2.length) {
                case 1:
                    if (var2[0].getName().equals("java.lang.String")) {
                        return 1;
                    }
                }
            }
            break;
        case -1776922004:
            if (var1.equals("toString")) {
                switch(var2.length) {
                case 0:
                    return 3;
                }
            }
            break;
        case -1295482945:
            if (var1.equals("equals")) {
                switch(var2.length) {
                case 1:
                    if (var2[0].getName().equals("java.lang.Object")) {
                        return 2;
                    }
                }
            }
            break;
        case 147696667:
            if (var1.equals("hashCode")) {
                switch(var2.length) {
                case 0:
                    return 4;
                }
            }
            break;
        case 510300177:
            if (var1.equals("dealTask")) {
                switch(var2.length) {
                case 1:
                    if (var2[0].getName().equals("java.lang.String")) {
                        return 0;
                    }
                }
            }
        }

        return -1;
    }

    public int getIndex(Class[] var1) {
        switch(var1.length) {
        case 0:
            return 0;
        default:
            return -1;
        }
    }

    public Object invoke(int var1, Object var2, Object[] var3) throws InvocationTargetException {
        ExecutionTimeReality var10000 = (ExecutionTimeReality)var2;
        int var10001 = var1;

        try {
            switch(var10001) {
            case 0:
                var10000.dealTask((String)var3[0]);
                return null;
            case 1:
                var10000.sayHello((String)var3[0]);
                return null;
            case 2:
                return new Boolean(var10000.equals(var3[0]));
            case 3:
                return var10000.toString();
            case 4:
                return new Integer(var10000.hashCode());
            }
        } catch (Throwable var4) {
            throw new InvocationTargetException(var4);
        }

        throw new IllegalArgumentException("Cannot find matching method/constructor");
    }

    public Object newInstance(int var1, Object[] var2) throws InvocationTargetException {
        ExecutionTimeReality var10000 = new ExecutionTimeReality;
        ExecutionTimeReality var10001 = var10000;
        int var10002 = var1;

        try {
            switch(var10002) {
            case 0:
                var10001.<init>();
                return var10000;
            }
        } catch (Throwable var3) {
            throw new InvocationTargetException(var3);
        }

        throw new IllegalArgumentException("Cannot find matching method/constructor");
    }

    public int getMaxIndex() {
        return 4;
    }
}