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Java中的cglib代理详解

作者：.番茄炒蛋

这篇文章主要介绍了Java中的cglib代理详解, 代理模式是一种设计模式,它可以为其他对象提供一种代理,以控制对该对象的访问,可以在运行时动态地创建代理对象,而不需要手动编写代理类的代码,需要的朋友可以参考下

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.NullPointerException
        enhancer.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.

在这里插入图片描述

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()

在这里插入图片描述

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

//
// 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$THREAD_CALLBACKS
  2. 获取DemoService类中的test方法的Method对象赋值给CGLIB$test0 00Method
  3. 构造test()方法所对应的MethodProxy对象赋值给CGLIB$test0 00Proxy

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:
    • 先生成类的定义,继承DemoService和实现Factory
    • 根据DemoService类中的方法生成代理类中对应的方法和属性
    • 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

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