CGLIB动态代理原理

被代理类

public class Human {
    void doThings() {
        System.out.println("Human");
    }
}

代理类

public class CglibProxyHuman implements MethodInterceptor {

    public Object getProxyInstance(Object target) {
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(target.getClass());
        enhancer.setCallback(this); //将自己传给增强类,调用this.intercept
        return enhancer.create();
    }

    @Override
    public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
        System.out.println("before target method...");
        Object result = methodProxy.invokeSuper(o, objects);
        System.out.println("after target method...");
        return result;
    }
}

测试代码

 public static void main(String[] args) {
        //调试查看动态代理生成文件
        System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "f:\\cglib");
        Human human= new Human();
        Human humanProxy=(Human)new CglibProxyHuman().getProxyInstance(human);
        humanProxy.doThings();
    }

查看动态代理生成文件，存储在 f:\\cglib

System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "f:\\cglib");

增强类

humanProxy对象对应的动态生成的增强类 Human$ $EnhancerByCGLIB$$b7eedfef

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 Human$$EnhancerByCGLIB$$b7eedfef extends Human implements Factory {
    private boolean CGLIB$BOUND;
    private static final ThreadLocal CGLIB$THREAD_CALLBACKS;
    private static final Callback[] CGLIB$STATIC_CALLBACKS;
    private MethodInterceptor CGLIB$CALLBACK_0;
    private static final Method CGLIB$doThings$0$Method;
    private static final MethodProxy CGLIB$doThings$0$Proxy;
    private static final Object[] CGLIB$emptyArgs;
    private static final Method CGLIB$finalize$1$Method;
    private static final MethodProxy CGLIB$finalize$1$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("cn.suning.cglib.Human$$EnhancerByCGLIB$$b7eedfef");
        Class var1;
        Method[] var10000 = ReflectUtils.findMethods(new String[]{"finalize", "()V", "equals", "(Ljava/lang/Object;)Z", "toString", "()Ljava/lang/String;", "hashCode", "()I", "clone", "()Ljava/lang/Object;"}, (var1 = Class.forName("java.lang.Object")).getDeclaredMethods());
        CGLIB$finalize$1$Method = var10000[0];
        CGLIB$finalize$1$Proxy = MethodProxy.create(var1, var0, "()V", "finalize", "CGLIB$finalize$1");
        CGLIB$equals$2$Method = var10000[1];
        CGLIB$equals$2$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/Object;)Z", "equals", "CGLIB$equals$2");
        CGLIB$toString$3$Method = var10000[2];
        CGLIB$toString$3$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/String;", "toString", "CGLIB$toString$3");
        CGLIB$hashCode$4$Method = var10000[3];
        CGLIB$hashCode$4$Proxy = MethodProxy.create(var1, var0, "()I", "hashCode", "CGLIB$hashCode$4");
        CGLIB$clone$5$Method = var10000[4];
        CGLIB$clone$5$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/Object;", "clone", "CGLIB$clone$5");
        CGLIB$doThings$0$Method = ReflectUtils.findMethods(new String[]{"doThings", "()V"}, (var1 = Class.forName("cn.suning.cglib.Human")).getDeclaredMethods())[0];
        CGLIB$doThings$0$Proxy = MethodProxy.create(var1, var0, "()V", "doThings", "CGLIB$doThings$0");
    }

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

    /*
    * humanProxy.doThings()
    */
    final void doThings() {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            // CglibProxyHuman 类中 intercept
            var10000.intercept(this, CGLIB$doThings$0$Method, CGLIB$emptyArgs, CGLIB$doThings$0$Proxy);
        } else {
            super.doThings();
        }
    }

    ....................省略部分无关代码............................    

    public Human$$EnhancerByCGLIB$$b7eedfef() {
        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) {
        Human$$EnhancerByCGLIB$$b7eedfef var1 = (Human$$EnhancerByCGLIB$$b7eedfef)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);
        Human$$EnhancerByCGLIB$$b7eedfef var10000 = new Human$$EnhancerByCGLIB$$b7eedfef();
        CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
        return var10000;
    }

    public Object newInstance(Callback var1) {
        CGLIB$SET_THREAD_CALLBACKS(new Callback[]{var1});
        Human$$EnhancerByCGLIB$$b7eedfef var10000 = new Human$$EnhancerByCGLIB$$b7eedfef();
        CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
        return var10000;
    }

    public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) {
        CGLIB$SET_THREAD_CALLBACKS(var3);
        Human$$EnhancerByCGLIB$$b7eedfef var10000 = new Human$$EnhancerByCGLIB$$b7eedfef;
        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();
    }
}

humanProxy.doThings() 相当于调用 Human$ $EnhancerByCGLIB$$b7eedfef 类中的doThings方法

 final void doThings() {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }
        if (var10000 != null) {
            // CglibProxyHuman 类中 intercept
            var10000.intercept(this, CGLIB$doThings$0$Method, CGLIB$emptyArgs, CGLIB$doThings$0$Proxy);
        } else {
            super.doThings();
        }
    }

然后 var10000.intercept  相当于调用  CglibProxyHuman 类中 intercept 方法

 @Override
 public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
        System.out.println("before target method...");
        Object result = methodProxy.invokeSuper(o, objects);
        System.out.println("after target method...");
        return result;
 }

然后执行methodProxy.invokeSuper(o, objects)

public Object invokeSuper(Object obj, Object[] args) throws Throwable {
        try {
            this.init();
            MethodProxy.FastClassInfo fci = this.fastClassInfo;
            return fci.f2.invoke(fci.i2, obj, args);
        } catch (InvocationTargetException var4) {
            throw var4.getTargetException();
        }
    }

fci.f2 的类型是动态代理类 Human$ $EnhancerByCGLIB$ $1a9e6f49$ $FastClassByCGLIB$$662b6cec 关键代码如下

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

public class Human$$EnhancerByCGLIB$$b7eedfef$$FastClassByCGLIB$$662b6cec extends FastClass {
    public Human$$EnhancerByCGLIB$$b7eedfef$$FastClassByCGLIB$$662b6cec(Class var1) {
        super(var1);
    }

    ............此处省略部分代码................. 

    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 {
        1a9e6f49 var10000 = (1a9e6f49)var2;
        int var10001 = var1;

        try {
            switch(var10001) {
            case 0:
                return new Boolean(var10000.equals(var3[0]));
            case 1:
                return var10000.toString();
            case 2:
                return new Integer(var10000.hashCode());
            case 3:
                return var10000.newInstance((Class[])var3[0], (Object[])var3[1], (Callback[])var3[2]);
            case 4:
                return var10000.newInstance((Callback)var3[0]);
            case 5:
                return var10000.newInstance((Callback[])var3[0]);
            case 6:
                var10000.doThings();
                return null;
            case 7:
                var10000.setCallback(((Number)var3[0]).intValue(), (Callback)var3[1]);
                return null;
            case 8:
                var10000.setCallbacks((Callback[])var3[0]);
                return null;
            case 9:
                return var10000.getCallback(((Number)var3[0]).intValue());
            case 10:
                return var10000.getCallbacks();
            case 11:
                1a9e6f49.CGLIB$SET_STATIC_CALLBACKS((Callback[])var3[0]);
                return null;
            case 12:
                1a9e6f49.CGLIB$SET_THREAD_CALLBACKS((Callback[])var3[0]);
                return null;
            case 13:
                return 1a9e6f49.CGLIB$findMethodProxy((Signature)var3[0]);
            case 14:
                1a9e6f49.CGLIB$STATICHOOK1();
                return null;
            case 15:
                var10000.CGLIB$finalize$1();
                return null;
            case 16:
                return var10000.CGLIB$toString$3();
            case 17:
                return new Boolean(var10000.CGLIB$equals$2(var3[0]));
            case 18:
                return new Integer(var10000.CGLIB$hashCode$4());
            case 19:
                var10000.CGLIB$doThings$0();
                return null;
            case 20:
                return var10000.CGLIB$clone$5();
            case 21:
                var10000.wait();
                return null;
            case 22:
                var10000.wait(((Number)var3[0]).longValue(), ((Number)var3[1]).intValue());
                return null;
            case 23:
                var10000.wait(((Number)var3[0]).longValue());
                return null;
            case 24:
                return var10000.getClass();
            case 25:
                var10000.notify();
                return null;
            case 26:
                var10000.notifyAll();
                return null;
            }
        } catch (Throwable var4) {
            throw new InvocationTargetException(var4);
        }

        throw new IllegalArgumentException("Cannot find matching method/constructor");
    }

    public Object newInstance(int var1, Object[] var2) throws InvocationTargetException {
        1a9e6f49 var10000 = new 1a9e6f49;
        1a9e6f49 var10001 = var10000;
        int var10002 = var1;

        try {
            switch(var10002) {
            case 0:
                var10001.();
                return var10000;
            }
        } catch (Throwable var3) {
            throw new InvocationTargetException(var3);
        }

        throw new IllegalArgumentException("Cannot find matching method/constructor");
    }

    public int getMaxIndex() {
        return 26;
    }
}

fci.f2.invoke(fci.i2, obj, args) 其实调用是 Human$ $EnhancerByCGLIB$ $b7eedfef$ $FastClassByCGLIB$$662b6cec 类的 invoke 的方法，然后 fci.i2 的值是19

 case 19:
     var10000.CGLIB$doThings$0();
     return null;

然后调用  var10000.CGLIB$doThings$0 方法，var10000 的类型是 Human$ $EnhancerByCGLIB$$b7eedfef 类，相当于又调用Human$ $EnhancerByCGLIB$$b7eedfef 类中的 CGLIB$doThings$0 方法

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

super 是什么，super 是 Human 类

public class Human {
    void doThings() {
        System.out.println("Human");
    }
}

这样就调用 Human 类中的 doThings 方法