cglib代理解析

工作原理

• 使用

      <dependency><groupId>cglib</groupId><artifactId>cglib</artifactId><version>3.3.0</version></dependency>

对类和接口分别进行代理

• DemoService

package com.fanqiechaodan.user.service;/*** @author fanqiechaodan* @Classname DemoService* @Description* @Date 2023/3/1 19:44*/
public class DemoService {public void test(){System.out.println("==================>test");}
}

• DemoInterface

package com.fanqiechaodan.user.service;/*** @author fanqiechaodan* @Classname DemoInterface* @Description* @Date 2023/3/1 19:56*/
public interface DemoInterface {void test();
}

• Demo

package com.fanqiechaodan.user;import com.fanqiechaodan.user.service.DemoInterface;
import com.fanqiechaodan.user.service.DemoService;
import net.sf.cglib.proxy.Callback;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;/*** @author fanqiechaodan* @Classname Main* @Description* @Date 2023/3/1 19:47*/
public class Demo {public static void main(String[] args) {final DemoService target = new DemoService();Enhancer enhancer = new Enhancer();enhancer.setSuperclass(DemoService.class);// 必须设置callbacks不然会出现java.lang.NullPointerExceptionenhancer.setCallbacks(new Callback[]{(MethodInterceptor) (o, method, objects, methodProxy) -> {// test方法增强逻辑if ("test".equals(method.getName())) {System.out.println("方法执行前增强...");Object res = method.invoke(target, objects);System.out.println("方法执行后增强...");return res;}// 其他方法正常执行return method.invoke(target, objects);}});DemoService demoService = (DemoService) enhancer.create();demoService.test();Enhancer enhancer1 = new Enhancer();enhancer1.setSuperclass(DemoInterface.class);enhancer1.setCallbacks(new Callback[]{(MethodInterceptor) (o, method, objects, methodProxy) -> {// test方法增强逻辑if ("test".equals(method.getName())) {System.out.println("切面逻辑...");}return null;}});DemoInterface demo = (DemoInterface) enhancer1.create();demo.test();}
}

代码执行前设置VM options:

-Dcglib.debugLocation=根据自己实际情况填写

运行代码是cglib就会将生成的代理类放到上面所指定的路径上.

• DemoService代理类

public class DemoService$$EnhancerByCGLIB$$1c9ab053 extends DemoService implements Factory {// 省去不重要代码...final void CGLIB$test$0() {super.test();}public final void test() {MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;if (var10000 == null) {CGLIB$BIND_CALLBACKS(this);var10000 = this.CGLIB$CALLBACK_0;}if (var10000 != null) {var10000.intercept(this, CGLIB$test$0$Method, CGLIB$emptyArgs, CGLIB$test$0$Proxy);} else {super.test();}}// 省去不重要代码...
}

• DemoInterface代理类

public class DemoInterface$$EnhancerByCGLIB$$536bfe99 implements DemoInterface, Factory {// 省去不重要代码...final void CGLIB$test$4() {super.test();}public final void test() {MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;if (var10000 == null) {CGLIB$BIND_CALLBACKS(this);var10000 = this.CGLIB$CALLBACK_0;}if (var10000 != null) {var10000.intercept(this, CGLIB$test$4$Method, CGLIB$emptyArgs, CGLIB$test$4$Proxy);} else {super.test();}}// 省去不重要代码...
}

    final void CGLIB$test$0() {super.test();}

这个方法我们并不能直接调用,而是要通过所设置的Callback,也就是MethodInterceptor中的methodProxy来调用,methodProxy表示方法代理,假如DemoService代理对象在执行test()方法,那么当执行流程进入到intercept方法时,methodProxy表示的就是test()方法,DemoService和DemoService代理类中都有test(),所以methodProxy代理的就是这两个test()

工作原理:cglib会根据所设置得superclass,生成代理类作为其子类,并且会重写superclass中需要代理得方法,比如test(),相应得再代理类中会有两个方法,一个是重写的test(),用来执行增强逻辑,一个是CGLIB$test$0(),会直接调用super.test(),是让MethodProxy对象来用的

代理类生成逻辑

• DemoService代理类全部代码

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//package com.fanqiechaodan.user.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 DemoService$$EnhancerByCGLIB$$1c9ab053 extends DemoService 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$test$0$Method;private static final MethodProxy CGLIB$test$0$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.fanqiechaodan.user.service.DemoService$$EnhancerByCGLIB$$1c9ab053");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$1$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$4");CGLIB$test$0$Method = ReflectUtils.findMethods(new String[]{"test", "()V"}, (var1 = Class.forName("com.fanqiechaodan.user.service.DemoService")).getDeclaredMethods())[0];CGLIB$test$0$Proxy = MethodProxy.create(var1, var0, "()V", "test", "CGLIB$test$0");}final void CGLIB$test$0() {super.test();}public final void test() {MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;if (var10000 == null) {CGLIB$BIND_CALLBACKS(this);var10000 = this.CGLIB$CALLBACK_0;}if (var10000 != null) {var10000.intercept(this, CGLIB$test$0$Method, CGLIB$emptyArgs, CGLIB$test$0$Proxy);} else {super.test();}}final boolean CGLIB$equals$1(Object var1) {return super.equals(var1);}public final boolean equals(Object var1) {MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;if (var10000 == null) {CGLIB$BIND_CALLBACKS(this);var10000 = this.CGLIB$CALLBACK_0;}if (var10000 != null) {Object var2 = var10000.intercept(this, CGLIB$equals$1$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 (var10000 == 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 (var10000 == 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 (var10000 == 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$findMethodProxy(Signature var0) {String var10000 = var0.toString();switch(var10000.hashCode()) {case -1422510685:if (var10000.equals("test()V")) {return CGLIB$test$0$Proxy;}break;case -508378822:if (var10000.equals("clone()Ljava/lang/Object;")) {return CGLIB$clone$4$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 DemoService$$EnhancerByCGLIB$$1c9ab053() {CGLIB$BIND_CALLBACKS(this);}// 将代码中设置的callbacks设置到CGLIB$THREAD_CALLBACKS这个ThreadLocal中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) {DemoService$$EnhancerByCGLIB$$1c9ab053 var1 = (DemoService$$EnhancerByCGLIB$$1c9ab053)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);DemoService$$EnhancerByCGLIB$$1c9ab053 var10000 = new DemoService$$EnhancerByCGLIB$$1c9ab053();CGLIB$SET_THREAD_CALLBACKS((Callback[])null);return var10000;}public Object newInstance(Callback var1) {CGLIB$SET_THREAD_CALLBACKS(new Callback[]{var1});DemoService$$EnhancerByCGLIB$$1c9ab053 var10000 = new DemoService$$EnhancerByCGLIB$$1c9ab053();CGLIB$SET_THREAD_CALLBACKS((Callback[])null);return var10000;}public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) {CGLIB$SET_THREAD_CALLBACKS(var3);DemoService$$EnhancerByCGLIB$$1c9ab053 var10000 = new DemoService$$EnhancerByCGLIB$$1c9ab053;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();}
}

代理类中有一个静态代码块,会调用CGLIB$STATICHOOK1(),这个方法主要是为了给属性赋值,例如:

1. 构造一个ThreadLocal对象赋值给CGLIB$THREAD_CALLBACKS
2. 获取DemoService类中的test方法的Method对象赋值给CGLIB$test$0$Method
3. 构造test()方法所对应的MethodProxy对象赋值给CGLIB$test$0$Proxy

DemoService的代理类即继承了DemoService,也实现了Factory接口,从而就需要实现Factory接口中的方法

public interface Factory {Object newInstance(Callback callback);Object newInstance(Callback[] callbacks);Object newInstance(Class[] types, Object[] args, Callback[] callbacks);Callback getCallback(int index);void setCallback(int index, Callback callback);void setCallbacks(Callback[] callbacks);Callback[] getCallbacks();
}

newInstance方法会重新生成一个代理对象,setCallbacks()和getCallbacks()用来设置或获取增强逻辑

代理类大致流程是:

1. cglib先生成代理类,具体逻辑为:
   1. 先生成类的定义,继承DemoService和实现Factory
   2. 根据DemoService类中的方法生成代理类中对应的方法和属性
   3. 生成一些辅助的属性和方法
2. 然后调用构造方法得到代理对象
3. 然后cglib调用代理对象的CGLIB$SET_THREAD_CALLBACKS()方法,将我们自己所设置的callbacks设置到CGLIB$THREAD_CALLBACKS这个ThreadLocal中
4. 后续代理对象再执行test()方法时,就会从CGLIB$THREAD_CALLBACKS拿到所设置的callbacks,调用其intercept()方法