CGLIB動(dòng)態(tài)代理

知識(shí)回顧

在文章初識(shí)AOP中，了解到為什么要用代理，靜態(tài)代理和動(dòng)態(tài)代理的區(qū)別，在JDK的動(dòng)態(tài)代理中講到JDK的動(dòng)態(tài)代理是如何實(shí)現(xiàn)的，有什么優(yōu)缺點(diǎn)，本篇將繼續(xù)聊下CGLIB中動(dòng)態(tài)代理是如何實(shí)現(xiàn)的。

定義一個(gè)IHello的接口和一個(gè)Hello的實(shí)現(xiàn)類如下

package seven.com.seven.aop;

public interface IHello {

    void say();

}

package seven.com.seven.aop;

public class Hello implements IHello {

    @Override
    public void say() {
        System.out.println("hello word");
    }
}

CGLIB的動(dòng)態(tài)代理類如下

package seven.com.seven.aop;

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;

public class DynamicCGLibProxy  implements MethodInterceptor {

    /**
     * 被代理對(duì)象
     */
    private Object target;


    public Object getProxy(Object target){
        // 代理類class文件存入本地磁盤方便我們反編譯查看源碼
        System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "D:\\code");
        this.target=target;
        /**
         * 動(dòng)態(tài)代碼生成器
         */
        Enhancer enhancer=new Enhancer();
        enhancer.setSuperclass(target.getClass());
        enhancer.setCallback(this);

        /**
         * 動(dòng)態(tài)生成字節(jié)碼并返回代理對(duì)象
         */
        return enhancer.create();
    }

    @Override
    public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
        long star = System.currentTimeMillis();
        Object result = proxy.invokeSuper(obj,args);
        long end = System.currentTimeMillis();
        System.out.println(String.format("method cost %s", (end - star)));
        return result;
    }
}


package seven.com;

import seven.com.seven.aop.DynamicCGLibProxy;
import seven.com.seven.aop.DynamicJDKProxy;
import seven.com.seven.aop.Hello;
import seven.com.seven.aop.IHello;

public class App {
    public static void main(String[] args) {
        Hello hello = new Hello();
        IHello proxy = (IHello) new DynamicCGLibProxy().getProxy(hello);
        proxy.say();
    }
}

分析生成的代理類

通過(guò)設(shè)置參數(shù)System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "D:\code");，可以把生成的代理類保存到磁盤中，我們可以在指定目錄中看到自動(dòng)生成的文件不止一個(gè),反編譯看下其中Hello類的代理類源碼如下，如果耐著性子仔細(xì)分析下就不難看出，其實(shí)動(dòng)態(tài)代理類是在靜態(tài)構(gòu)造函數(shù)中把每一個(gè)父類的方法分別對(duì)應(yīng)創(chuàng)建了一個(gè)MethodProxy對(duì)象，也就是方法代理對(duì)象

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

package seven.com.seven.aop;

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 Hello$$EnhancerByCGLIB$$f0ec8381 extends Hello 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$say$0$Method;
    private static final MethodProxy CGLIB$say$0$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;

        /**
         * 這里是根據(jù)所繼承的類（包括Object），查找出所有方法（非final），然后分別生成對(duì)應(yīng)的MethodProxy對(duì)象，也就是方法的代理對(duì)象，最終傳入到MethodInterceptor的intercept方法的最后一個(gè)參數(shù)中
         */
    static void CGLIB$STATICHOOK1() {
        CGLIB$THREAD_CALLBACKS = new ThreadLocal();
        CGLIB$emptyArgs = new Object[0];
        Class var0 = Class.forName("seven.com.seven.aop.Hello$$EnhancerByCGLIB$$f0ec8381");
        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$4");
        CGLIB$say$0$Method = ReflectUtils.findMethods(new String[]{"say", "()V"}, (var1 = Class.forName("seven.com.seven.aop.Hello")).getDeclaredMethods())[0];
        CGLIB$say$0$Proxy = MethodProxy.create(var1, var0, "()V", "say", "CGLIB$say$0");
    }

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

        /**
         * 執(zhí)行方法時(shí)判斷是否有callback（MethodInterceptor 類型的對(duì)象），有的話是執(zhí)行其intercept方法，并且傳入上面生成的MethodProxy對(duì)象
         */
    public final void say() {
        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$say$0$Method, CGLIB$emptyArgs, CGLIB$say$0$Proxy);
        } else {
            super.say();
        }
    }

    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$findMethodProxy(Signature var0) {
        String var10000 = var0.toString();
        switch(var10000.hashCode()) {
        case -909388886:
            if (var10000.equals("say()V")) {
                return CGLIB$say$0$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 Hello$$EnhancerByCGLIB$$f0ec8381() {
        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) {
        Hello$$EnhancerByCGLIB$$f0ec8381 var1 = (Hello$$EnhancerByCGLIB$$f0ec8381)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);
        Hello$$EnhancerByCGLIB$$f0ec8381 var10000 = new Hello$$EnhancerByCGLIB$$f0ec8381();
        CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
        return var10000;
    }

    public Object newInstance(Callback var1) {
        CGLIB$SET_THREAD_CALLBACKS(new Callback[]{var1});
        Hello$$EnhancerByCGLIB$$f0ec8381 var10000 = new Hello$$EnhancerByCGLIB$$f0ec8381();
        CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
        return var10000;
    }

    public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) {
        CGLIB$SET_THREAD_CALLBACKS(var3);
        Hello$$EnhancerByCGLIB$$f0ec8381 var10000 = new Hello$$EnhancerByCGLIB$$f0ec8381;
        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();
    }
}
解析
  1. 動(dòng)態(tài)代理類是在靜態(tài)構(gòu)造函數(shù)中把每一個(gè)父類的方法分別對(duì)應(yīng)創(chuàng)建了一個(gè)MethodProxy對(duì)象，也就是方法代理對(duì)象
  2. 執(zhí)行對(duì)應(yīng)方法時(shí)，比如Hello類中的say方法，會(huì)先判斷是否存在CallBack，也就是創(chuàng)建代理類時(shí)enhancer.setCallback(this);這句代碼指定的callback，因?yàn)閏allback本身是MethodInterceptor類型，如果存在則執(zhí)行其intercept方法，這也就解釋了為什么最終會(huì)執(zhí)行到我們定義的DynamicCGLibProxy的中，因?yàn)樗褪菍?shí)現(xiàn)了MethodInterceptor接口的callback，執(zhí)行到這里我們自然可以在方法前后做一些攔截，增強(qiáng)原始對(duì)象的功能，達(dá)到代理的目的

CGLIB的動(dòng)態(tài)代理

MethodInterceptor

public interface MethodInterceptor
extends Callback
{  
  /**
     * 被代理的對(duì)象的方法最終會(huì)執(zhí)行到這里，在這里可以在方法執(zhí)行前后做一些攔截，
     * 增加一些邏輯，甚至可以不執(zhí)行原來(lái)的方法，執(zhí)行方法通過(guò)MethodProxy 
     * 這個(gè)方法代理對(duì)象來(lái)執(zhí)行
     * @param obj  最終生成的代理對(duì)象，也就是上面源碼中看到的
     * @param method 被攔截的方法
     * @param args  被攔截的方法的參數(shù)集合
     * @param proxy 方法的代理對(duì)象，如上面解釋CGLIB會(huì)把生成的代理類父類【本例中為Hello和Object】中的每個(gè)方法都單獨(dú)生成一個(gè)MethodProxy，用來(lái)最終執(zhí)行父類的方法
     */ 
    public Object intercept(Object obj, java.lang.reflect.Method method, Object[] args,
                               MethodProxy proxy) throws Throwable;

}

MethodProxy

package net.sf.cglib.proxy;
public class MethodProxy {

    /**
     * 通過(guò)此方法執(zhí)行原對(duì)象（被代理的對(duì)象）的方法，可以看到是執(zhí)行fci.f2.invoke,在文章開篇就講到生成的代理類不止一個(gè)，這里其實(shí)最終是實(shí)行了繼承了FastClass的一個(gè)代理類Hello$$FastClassByCGLIB$$c45ea757，最終執(zhí)行了被代理對(duì)象的方法
     * @param obj 生成的代理的對(duì)象
     * @param args 方法的參數(shù)
     */
    public Object invokeSuper(Object obj, Object[] args) throws Throwable {
        try {
            init();
            FastClassInfo fci = fastClassInfo;
            return fci.f2.invoke(fci.i2, obj, args);
        } catch (InvocationTargetException e) {
            throw e.getTargetException();
        }
    }
}

下面是和代理類一起生成的其中一個(gè)繼承自FastClass的類文件，當(dāng)執(zhí)行MethodProxy的invokeSuper方法時(shí)其實(shí)就是執(zhí)行這個(gè)對(duì)象的invoke方法

package seven.com.seven.aop;

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

public class Hello$$FastClassByCGLIB$$c45ea757 extends FastClass {
    public Hello$$FastClassByCGLIB$$c45ea757(Class var1) {
        super(var1);
    }

    public int getIndex(Signature var1) {
        String var10000 = var1.toString();
        switch(var10000.hashCode()) {
        case -909388886:
            if (var10000.equals("say()V")) {
                return 0;
            }
            break;
        case 1826985398:
            if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
                return 1;
            }
            break;
        case 1913648695:
            if (var10000.equals("toString()Ljava/lang/String;")) {
                return 2;
            }
            break;
        case 1984935277:
            if (var10000.equals("hashCode()I")) {
                return 3;
            }
        }

        return -1;
    }

    public int getIndex(String var1, Class[] var2) {
        switch(var1.hashCode()) {
        case -1776922004:
            if (var1.equals("toString")) {
                switch(var2.length) {
                case 0:
                    return 2;
                }
            }
            break;
        case -1295482945:
            if (var1.equals("equals")) {
                switch(var2.length) {
                case 1:
                    if (var2[0].getName().equals("java.lang.Object")) {
                        return 1;
                    }
                }
            }
            break;
        case 113643:
            if (var1.equals("say")) {
                switch(var2.length) {
                case 0:
                    return 0;
                }
            }
            break;
        case 147696667:
            if (var1.equals("hashCode")) {
                switch(var2.length) {
                case 0:
                    return 3;
                }
            }
        }

        return -1;
    }

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

    /**
     * 上面MethodProxy的invoke方法最終會(huì)執(zhí)行到這里，也就是執(zhí)行被代理對(duì)象的具體方法上
     */ 
    public Object invoke(int var1, Object var2, Object[] var3) throws InvocationTargetException {
        Hello var10000 = (Hello)var2;
        int var10001 = var1;

        try {
            switch(var10001) {
            case 0:
                var10000.say();
                return null;
            case 1:
                return new Boolean(var10000.equals(var3[0]));
            case 2:
                return var10000.toString();
            case 3:
                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 {
        Hello var10000 = new Hello;
        Hello 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 3;
    }
}

JDK動(dòng)態(tài)代理和CGLIB字節(jié)碼生成的區(qū)別

  1. JDK動(dòng)態(tài)代理只能對(duì)實(shí)現(xiàn)了接口的類生成代理，而不能針對(duì)類。
  2. CGLIB是針對(duì)類實(shí)現(xiàn)代理，主要是對(duì)指定的類生成一個(gè)子類，覆蓋其中的方法，
    并覆蓋其中方法實(shí)現(xiàn)增強(qiáng)，但是因?yàn)椴捎玫氖抢^承，所以該類或方法最好不要聲明成final，
    對(duì)于final類或方法，是無(wú)法繼承的

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