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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 {@Overridepublic 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└─aExecutionTimeReality$$EnhancerByCGLIB$$5a92c386$$FastClassByCGLIB$$bebee033.classExecutionTimeReality$$EnhancerByCGLIB$$5a92c386.classExecutionTimeReality$$FastClassByCGLIB$$81389d66.class

因为两个$在CSDN中显示不正常，所以下边用一个$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;}
}

其他网址

JDK动态代理和CGLIB代理的区别_学无止境! 无休无止! -CSDN博客

Cglib动态代理实现原理 - 糖豆包子 - 博客园