动态代理 （CGLIB 动态代理）
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动态代理： 代理类在程序运行时被创建，这种代理方式称为动态代理
动态代理实现有两种方式，JDK 动态代理和 CGlib 动态代理，本文介绍 CGlib 动态代理
CGLib 动态代理：采用底层的字节码技术，可以为一个类创建子类，在子类中采用方法拦截的技术拦截所有父类方法的调用，并在调用中添加横切逻辑
CGLib 动态代理示例代码
创建一个普通 maven 工程，引入 CGLib 依赖
4.0.0 com.cglibdynamicproxy cglibdynamicproxy 0.0.1-SNAPSHOT cglibdynamicproxy cglib cglib 3.2.5 maven-compiler-plugin 1.8 1.8
创建被代理类
package com.cglibdynamicproxy.service;/** * 被代理类 * @author Administrator */public class AgentTarget { public void proxyMethod() { System.out.println("被代理的方法执行了");; }} 创建 CglibMethodInterceptor 类，实现 MethodInterceptor
package com.cglibdynamicproxy.cglib;import java.lang.reflect.Method;import net.sf.cglib.proxy.MethodInterceptor;import net.sf.cglib.proxy.MethodProxy;public class CglibMethodInterceptor implements MethodInterceptor{ /** * 拦截父类所有方法的调用 */ @Override public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable { //obj 目标类的实例 //method 目标类方法的反射对象 //args 方法的动态入参 //proxy 代理类实例 System.out.println("before"); Object res = null; try{ //反射调用目标对象方法 res = proxy.invokeSuper(obj, args); }catch (Exception e){ System.out.println("e:" + e.getMessage()); throw e; }finally { System.out.println("after"); } return res; }} 测试类
package com.cglibdynamicproxy;import com.cglibdynamicproxy.cglib.CglibMethodInterceptor;import com.cglibdynamicproxy.service.AgentTarget;import net.sf.cglib.core.DebuggingClassWriter;import net.sf.cglib.proxy.Enhancer;public class CglibDynamicProxyMain { public static void main(String[] args) { //将生成的class文件保存到指定目录，这里是项目目录 System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "E:\\workspace\\cglibdynamicproxy"); Enhancer enhancer = new Enhancer(); //设置父类 enhancer.setSuperclass(AgentTarget.class); //设置回调函数 enhancer.setCallback(new CglibMethodInterceptor()); //创建AgentTarget.class的子类 AgentTarget childAgentTarget = (AgentTarget) enhancer.create(); //调用方法 childAgentTarget.proxyMethod(); }} 运行如下
生成的 class 文件
重点看生成的这个文件 AgentTarget$$EnhancerByCGLIB$$303de0ca.class
代码如下
package com.cglibdynamicproxy.service;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 AgentTarget$$EnhancerByCGLIB$$303de0ca extends AgentTarget 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$proxyMethod$0$Method; private static final MethodProxy CGLIB$proxyMethod$0$Proxy; private static final Object[] CGLIB$emptyArgs; private static final Method CGLIB$equals$1$Method; private static final MethodProxy CGLIB$equals$1$Proxy; private static final Method CGLIB$toString$2$Method; private static final MethodProxy CGLIB$toString$2$Proxy; private static final Method CGLIB$hashCode$3$Method; private static final MethodProxy CGLIB$hashCode$3$Proxy; private static final Method CGLIB$clone$4$Method; private static final MethodProxy CGLIB$clone$4$Proxy; static void CGLIB$STATICHOOK1() { CGLIB$THREAD_CALLBACKS = new ThreadLocal(); CGLIB$emptyArgs = new Object[0]; Class var0 = Class.forName("com.cglibdynamicproxy.service.AgentTarget$$EnhancerByCGLIB$$303de0ca"); Class var1; CGLIB$proxyMethod$0$Method = ReflectUtils.findMethods(new String[]{"proxyMethod", "()V"}, (var1 = Class.forName("com.cglibdynamicproxy.service.AgentTarget")).getDeclaredMethods())[0]; CGLIB$proxyMethod$0$Proxy = MethodProxy.create(var1, var0, "()V", "proxyMethod", "CGLIB$proxyMethod$0"); Method[] var10000 = ReflectUtils.findMethods( new String[]{"equals", "(Ljava/lang/Object;)Z", "toString", "()Ljava/lang/String;", "hashCode", "()I", "clone", "()Ljava/lang/Object;"}, (var1 = Class.forName("java.lang.Object")).getDeclaredMethods()); CGLIB$equals$1$Method = var10000[0]; CGLIB$equals$1$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/Object;)Z", "equals", "CGLIB$equals$1"); CGLIB$toString$2$Method = var10000[1]; CGLIB$toString$2$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/String;", "toString", "CGLIB$toString$2"); CGLIB$hashCode$3$Method = var10000[2]; CGLIB$hashCode$3$Proxy = MethodProxy.create(var1, var0, "()I", "hashCode", "CGLIB$hashCode$3"); CGLIB$clone$4$Method = var10000[3]; CGLIB$clone$4$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/Object;", "clone", "CGLIB$clone$4"); } final void CGLIB$proxyMethod$0() { super.proxyMethod(); } public final void proxyMethod() { MethodInterceptor var10000 = this.CGLIB$CALLBACK_0; if (this.CGLIB$CALLBACK_0 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_0; } if (var10000 != null) { var10000.intercept(this, CGLIB$proxyMethod$0$Method, CGLIB$emptyArgs, CGLIB$proxyMethod$0$Proxy); } else { super.proxyMethod(); } } final boolean CGLIB$equals$1(Object var1) { return super.equals(var1); } public final boolean equals(Object var1) { MethodInterceptor var10000 = this.CGLIB$CALLBACK_0; if (this.CGLIB$CALLBACK_0 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_0; } if (var10000 != null) { Object var2 = var10000.intercept(this, CGLIB$equals$1$Method, new Object[]{var1}, CGLIB$equals$1$Proxy); return var2 == null ? false : (Boolean) var2; } else { return super.equals(var1); } } final String CGLIB$toString$2() { return super.toString(); } public final String toString() { MethodInterceptor var10000 = this.CGLIB$CALLBACK_0; if (this.CGLIB$CALLBACK_0 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_0; } return var10000 != null ? (String) var10000.intercept(this, CGLIB$toString$2$Method, CGLIB$emptyArgs, CGLIB$toString$2$Proxy) : super.toString(); } final int CGLIB$hashCode$3() { return super.hashCode(); } public final int hashCode() { MethodInterceptor var10000 = this.CGLIB$CALLBACK_0; if (this.CGLIB$CALLBACK_0 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_0; } if (var10000 != null) { Object var1 = var10000.intercept(this, CGLIB$hashCode$3$Method, CGLIB$emptyArgs, CGLIB$hashCode$3$Proxy); return var1 == null ? 0 : ((Number) var1).intValue(); } else { return super.hashCode(); } } final Object CGLIB$clone$4() throws CloneNotSupportedException { return super.clone(); } protected final Object clone() throws CloneNotSupportedException { MethodInterceptor var10000 = this.CGLIB$CALLBACK_0; if (this.CGLIB$CALLBACK_0 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_0; } return var10000 != null ? var10000.intercept(this, CGLIB$clone$4$Method, CGLIB$emptyArgs, CGLIB$clone$4$Proxy) : super.clone(); } public static MethodProxy CGLIB$findMethodProxy(Signature var0) { String var10000 = var0.toString(); switch (var10000.hashCode()) { case -508378822 : if (var10000.equals("clone()Ljava/lang/Object;")) { return CGLIB$clone$4$Proxy; } break; case -472693722 : if (var10000.equals("proxyMethod()V")) { return CGLIB$proxyMethod$0$Proxy; } break; case 1826985398 : if (var10000.equals("equals(Ljava/lang/Object;)Z")) { return CGLIB$equals$1$Proxy; } break; case 1913648695 : if (var10000.equals("toString()Ljava/lang/String;")) { return CGLIB$toString$2$Proxy; } break; case 1984935277 : if (var10000.equals("hashCode()I")) { return CGLIB$hashCode$3$Proxy; } } return null; } public AgentTarget$$EnhancerByCGLIB$$303de0ca() { 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) { AgentTarget$$EnhancerByCGLIB$$303de0ca var1 = (AgentTarget$$EnhancerByCGLIB$$303de0ca) var0; if (!var1.CGLIB$BOUND) { var1.CGLIB$BOUND = true; Object var10000 = CGLIB$THREAD_CALLBACKS.get(); if (var10000 == null) { var10000 = CGLIB$STATIC_CALLBACKS; if (CGLIB$STATIC_CALLBACKS == null) { return; } } var1.CGLIB$CALLBACK_0 = (MethodInterceptor) ((Callback[]) var10000)[0]; } } public Object newInstance(Callback[] var1) { CGLIB$SET_THREAD_CALLBACKS(var1); AgentTarget$$EnhancerByCGLIB$$303de0ca var10000 = new AgentTarget$$EnhancerByCGLIB$$303de0ca(); CGLIB$SET_THREAD_CALLBACKS((Callback[]) null); return var10000; } public Object newInstance(Callback var1) { CGLIB$SET_THREAD_CALLBACKS(new Callback[]{var1}); AgentTarget$$EnhancerByCGLIB$$303de0ca var10000 = new AgentTarget$$EnhancerByCGLIB$$303de0ca(); CGLIB$SET_THREAD_CALLBACKS((Callback[]) null); return var10000; } public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) { CGLIB$SET_THREAD_CALLBACKS(var3); AgentTarget$$EnhancerByCGLIB$$303de0ca var10000 = new AgentTarget$$EnhancerByCGLIB$$303de0ca; switch(var1.length) { case 0: var10000. (); 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(); }} 其中，这段代码为核心内容
public final void proxyMethod() { MethodInterceptor var10000 = this.CGLIB$CALLBACK_0; if (this.CGLIB$CALLBACK_0 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_0; } if (var10000 != null) { var10000.intercept(this, CGLIB$proxyMethod$0$Method, CGLIB$emptyArgs, CGLIB$proxyMethod$0$Proxy); } else { super.proxyMethod(); } } 程序运行流程：代理对象继承父类 AgentTarget，重写 proxyMethod 方法，拦截器调用 intercept 方法，intercept 方法由自定义的 CglibMethodInterceptor 实现，当调用 MyMethodInterceptor 中的 intercept 方法时，通过反射调用目标对象方法，从而完成了由代理对象访问到目标对象的动态代理
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