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Java中Cglib代理类重写逻辑详解

作者：ps酷教程

这篇文章主要介绍了Java中Cglib代理类重写逻辑详解,代理类中只会维护NoOp这个回调属性,并不会生成目标类MyService中的noOp所对应的方法,需要的朋友可以参考下

前言

要看懂Spring Aop，必须先看懂不同cglib回调类型所应用的方法，在代理类中的重写逻辑。

引入包

<dependency>
    <groupId>cglib</groupId>
    <artifactId>cglib</artifactId>
    <version>2.2.2</version>
</dependency>
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.12</version>
</dependency>

Callback回调

Callback_NoOp

public class Callback_NoOp implements NoOp {

}

Callback_MethodInterceptor

public class Callback_MethodInterceptor implements MethodInterceptor {

    @Override
    public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
        System.out.println("enter MethodInterceptor...");
        return null;

    }
}

Callback_LazyLoader

public class Callback_LazyLoader implements LazyLoader {

    @Override
    public Object loadObject() throws Exception {
        System.out.println("enter LazyLoader...");
        return null;
    }

}

Callback_InvocationHandler

public class Callback_InvocationHandler implements InvocationHandler {
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("enter InvocationHandler...");
        return null;
    }
}

Callback_FixedValue

public class Callback_FixedValue implements FixedValue {
    @Override
    public Object loadObject() throws Exception {
        System.out.println("enter Callback_FixedValue...");
        return null;
    }
}

Callback_Dispatcher

public class Callback_Dispatcher implements Dispatcher {
    @Override
    public Object loadObject() throws Exception {
        System.out.println("enter Callback_Dispatcher...");
        return null;
    }
}

CustomizedCallbackFilter

public class CustomizedCallbackFilter implements CallbackFilter {
    @Override
    public int accept(Method method) {
        String methodName = method.getName();
        switch (methodName) {
            case "noOp":
                return 0;
            case "methodInterceptor":
                return 1;
            case "lazyLoader":
                return 2;
            case "invocationHandler":
                return 3;
            case "fixedValue":
                return 4;
            case "dispatcher":
                return 5;
        }
        return 0;
    }
}

MyService

目标类

public class MyService {

    public void noOp() {
        System.out.println("myService no op");
    }

    public void methodInterceptor() {
        System.out.println("myService method interceptor");
    }

    public void lazyLoader() {
        System.out.println("myService lazy loader");
    }

    public void invocationHandler() {
        System.out.println("myService invocation handler");
    }

    public void fixedValue() {
        System.out.println("myService fixed value");
    }

    public void dispatcher() {
        System.out.println("myService dispatcher");
    }

}

Test01

public class Test01 {
    public static void main(String[] args) {

        System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "D:\\Projects\\learning\\proxy-dynamic-demo\\target\\classes");

        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(MyService.class);

        Callback_NoOp callback_noOp = new Callback_NoOp();
        Callback_MethodInterceptor callback_methodInterceptor = new Callback_MethodInterceptor();
        Callback_LazyLoader callback_lazyLoader = new Callback_LazyLoader();
        Callback_InvocationHandler callback_invocationHandler = new Callback_InvocationHandler();
        Callback_FixedValue callback_fixedValue = new Callback_FixedValue();
        Callback_Dispatcher callback_dispatcher = new Callback_Dispatcher();

        enhancer.setCallbacks(new Callback[]{
                callback_noOp,
                callback_methodInterceptor,
                callback_lazyLoader,
                callback_invocationHandler,
                callback_fixedValue,
                callback_dispatcher
        });

        enhancer.setCallbackFilter(new CustomizedCallbackFilter());

        Object enhancedObj = enhancer.create();

    }
}

结论

NoOp

代理类中只会维护NoOp这个回调属性，并不会生成目标类MyService中的noOp所对应的方法

MethodInterceptor

可见，代理类中生成了目标类MyService中的methodInterceptor方法所对应的 CGLIB$methodInterceptor$1 和 methodInterceptor方法 这种类型的回调最为常用，它里面利用了FastClass，这种FastClass建立了调用逻辑和方法签名和索引之间的映射关系，能够快速的根据索引找到所对应的调用逻辑。

final void CGLIB$methodInterceptor$1() {
	 // 直接调用父类的methodInterceptor方法 
     super.methodInterceptor();
 }

public final void methodInterceptor() {

	// 获取绑定的回调对象
    MethodInterceptor var10000 = this.CGLIB$CALLBACK_1;
    
    if (var10000 == null) {
        CGLIB$BIND_CALLBACKS(this);
        var10000 = this.CGLIB$CALLBACK_1;
    }
	
	// 如果有设置的话(框架里面一般都设置了)
    if (var10000 != null) {
    
    	// 第一个参数就是当前代理类对象this
    	// 第二个参数是MyService的methodInterceptor方法
    	// 第三个参数是参数，因为这个方法没有参数，就用固定的这个CGLIB$emptyArgs，如果有参数的话，就会传入方法的参数
   		// 最后一个参数是MethodProxy类型的，它与FastClass机制的使用相关
        var10000.intercept(this, CGLIB$methodInterceptor$1$Method, CGLIB$emptyArgs, CGLIB$methodInterceptor$1$Proxy);
    } else {
        super.methodInterceptor();
    }
}

LazyLoader

可见，代理类中生成了目标类MyService中的lazyLoader方法所对应的 lazyLoader 方法

public final void lazyLoader() {
    // 每次都会调用下面这个CGLIB$LOAD_PRIVATE_2()方法
    ((MyService)this.CGLIB$LOAD_PRIVATE_2()).lazyLoader();
}

private final synchronized Object CGLIB$LOAD_PRIVATE_2() {
	// 获取CGLIB$LAZY_LOADER_2属性，即绑定的回调对象
    Object var10000 = this.CGLIB$LAZY_LOADER_2;

	// 如果从CGLIB$LAZY_LOADER_2属性获取的是null，则走下面逻辑
	// 如果不为null，直接将结果返回，所以这种类型会将结果返回并保存，
	// 等下次调用，直接返回结果
	// 也就是说这种类型的回调对象只会被调用 1 次
    if (var10000 == null) {
        // 如果还未绑定
        LazyLoader var10001 = this.CGLIB$CALLBACK_2;
        if (var10001 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10001 = this.CGLIB$CALLBACK_2;
        }
        // 调用回调对象的loadObject方法，
        //     并将调用结果返回作为方法的返回值
        //     并将返回的结果设置给this.CGLIB$LAZY_LOADER_2属性
        var10000 = this.CGLIB$LAZY_LOADER_2 = var10001.loadObject();
    }
    
    // 返回调用结果或直接返回
    return var10000;
}

InvocationHandler

public final void invocationHandler() {
    try {
    	// 获取绑定的回调对象CGLIB$CALLBACK_3
        InvocationHandler var10000 = this.CGLIB$CALLBACK_3;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_3;
        }
		// 直接调用回调对象的invoke方法，参数CGLIB$invocationHandler$0是MyService中的invocationHandler方法
        var10000.invoke(this, CGLIB$invocationHandler$0, new Object[0]);
        
    } catch (Error | RuntimeException var1) {
        throw var1;
    } catch (Throwable var2) {
        throw new UndeclaredThrowableException(var2);
    }
}

FixedValue

public final void fixedValue() {

	 // 获取绑定的回调对象
     FixedValue var10000 = this.CGLIB$CALLBACK_4;
     
     if (var10000 == null) {
     	 // 如果还未绑定
         CGLIB$BIND_CALLBACKS(this);
         var10000 = this.CGLIB$CALLBACK_4;
     }
     
	 // 每次调用都会调用回调对象的loadObject方法
     var10000.loadObject();
 }

Dispatcher

public final void dispatcher() {
	
	// 获取绑定的回调对象
    Dispatcher var10000 = this.CGLIB$CALLBACK_5;
    
    if (var10000 == null) {
        CGLIB$BIND_CALLBACKS(this);
        var10000 = this.CGLIB$CALLBACK_5;
    }
    
    // 调用回调对象的loadObject方法，将返回的结果去调用dispatcher方法
    ((MyService)var10000.loadObject()).dispatcher();
}

[Cglib生成的代理类]

package com.zzhua.cglib.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.Dispatcher;
import net.sf.cglib.proxy.Factory;
import net.sf.cglib.proxy.FixedValue;
import net.sf.cglib.proxy.InvocationHandler;
import net.sf.cglib.proxy.LazyLoader;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
import net.sf.cglib.proxy.NoOp;
import net.sf.cglib.proxy.UndeclaredThrowableException;

public class MyService$$EnhancerByCGLIB$$91e58a41 extends MyService implements Factory {
    private boolean CGLIB$BOUND;
    private static final ThreadLocal CGLIB$THREAD_CALLBACKS;
    private static final Callback[] CGLIB$STATIC_CALLBACKS;
    private NoOp CGLIB$CALLBACK_0;
    private MethodInterceptor CGLIB$CALLBACK_1;
    private LazyLoader CGLIB$CALLBACK_2;
    private InvocationHandler CGLIB$CALLBACK_3;
    private FixedValue CGLIB$CALLBACK_4;
    private Dispatcher CGLIB$CALLBACK_5;
    private static final Method CGLIB$methodInterceptor$1$Method;
    private static final MethodProxy CGLIB$methodInterceptor$1$Proxy;
    private static final Object[] CGLIB$emptyArgs;
    private Object CGLIB$LAZY_LOADER_2;
    private static final Method CGLIB$invocationHandler$0;

    static void CGLIB$STATICHOOK1() {
        CGLIB$THREAD_CALLBACKS = new ThreadLocal();
        CGLIB$emptyArgs = new Object[0];
        Class var0 = Class.forName("com.zzhua.cglib.service.MyService$$EnhancerByCGLIB$$91e58a41");
        Class var1;
        CGLIB$methodInterceptor$1$Method = ReflectUtils.findMethods(new String[]{"methodInterceptor", "()V"}, (var1 = Class.forName("com.zzhua.cglib.service.MyService")).getDeclaredMethods())[0];
        CGLIB$methodInterceptor$1$Proxy = MethodProxy.create(var1, var0, "()V", "methodInterceptor", "CGLIB$methodInterceptor$1");
        CGLIB$invocationHandler$0 = Class.forName("com.zzhua.cglib.service.MyService").getDeclaredMethod("invocationHandler");
    }

    final void CGLIB$methodInterceptor$1() {
        super.methodInterceptor();
    }

    public final void methodInterceptor() {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_1;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_1;
        }

        if (var10000 != null) {
            var10000.intercept(this, CGLIB$methodInterceptor$1$Method, CGLIB$emptyArgs, CGLIB$methodInterceptor$1$Proxy);
        } else {
            super.methodInterceptor();
        }
    }

    public static MethodProxy CGLIB$findMethodProxy(Signature var0) {
        String var10000 = var0.toString();
        switch(var10000.hashCode()) {
        case -1368021391:
            if (var10000.equals("methodInterceptor()V")) {
                return CGLIB$methodInterceptor$1$Proxy;
            }
        }

        return null;
    }

    public final void lazyLoader() {
        ((MyService)this.CGLIB$LOAD_PRIVATE_2()).lazyLoader();
    }

    private final synchronized Object CGLIB$LOAD_PRIVATE_2() {
        Object var10000 = this.CGLIB$LAZY_LOADER_2;
        if (var10000 == null) {
            LazyLoader var10001 = this.CGLIB$CALLBACK_2;
            if (var10001 == null) {
                CGLIB$BIND_CALLBACKS(this);
                var10001 = this.CGLIB$CALLBACK_2;
            }

            var10000 = this.CGLIB$LAZY_LOADER_2 = var10001.loadObject();
        }

        return var10000;
    }

    public final void invocationHandler() {
        try {
            InvocationHandler var10000 = this.CGLIB$CALLBACK_3;
            if (var10000 == null) {
                CGLIB$BIND_CALLBACKS(this);
                var10000 = this.CGLIB$CALLBACK_3;
            }

            var10000.invoke(this, CGLIB$invocationHandler$0, new Object[0]);
        } catch (Error | RuntimeException var1) {
            throw var1;
        } catch (Throwable var2) {
            throw new UndeclaredThrowableException(var2);
        }
    }

    public final void fixedValue() {
        FixedValue var10000 = this.CGLIB$CALLBACK_4;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_4;
        }

        var10000.loadObject();
    }

    public final void dispatcher() {
        Dispatcher var10000 = this.CGLIB$CALLBACK_5;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_5;
        }

        ((MyService)var10000.loadObject()).dispatcher();
    }

    public MyService$$EnhancerByCGLIB$$91e58a41() {
        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) {
        MyService$$EnhancerByCGLIB$$91e58a41 var1 = (MyService$$EnhancerByCGLIB$$91e58a41)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;
                }
            }

            Callback[] var10001 = (Callback[])var10000;
            var1.CGLIB$CALLBACK_5 = (Dispatcher)((Callback[])var10000)[5];
            var1.CGLIB$CALLBACK_4 = (FixedValue)var10001[4];
            var1.CGLIB$CALLBACK_3 = (InvocationHandler)var10001[3];
            var1.CGLIB$CALLBACK_2 = (LazyLoader)var10001[2];
            var1.CGLIB$CALLBACK_1 = (MethodInterceptor)var10001[1];
            var1.CGLIB$CALLBACK_0 = (NoOp)var10001[0];
        }

    }

    public Object newInstance(Callback[] var1) {
        CGLIB$SET_THREAD_CALLBACKS(var1);
        MyService$$EnhancerByCGLIB$$91e58a41 var10000 = new MyService$$EnhancerByCGLIB$$91e58a41();
        CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
        return var10000;
    }

    public Object newInstance(Callback var1) {
        throw new IllegalStateException("More than one callback object required");
    }

    public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) {
        CGLIB$SET_THREAD_CALLBACKS(var3);
        MyService$$EnhancerByCGLIB$$91e58a41 var10000 = new MyService$$EnhancerByCGLIB$$91e58a41;
        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$BIND_CALLBACKS(this);
        Object var10000;
        switch(var1) {
        case 0:
            var10000 = this.CGLIB$CALLBACK_0;
            break;
        case 1:
            var10000 = this.CGLIB$CALLBACK_1;
            break;
        case 2:
            var10000 = this.CGLIB$CALLBACK_2;
            break;
        case 3:
            var10000 = this.CGLIB$CALLBACK_3;
            break;
        case 4:
            var10000 = this.CGLIB$CALLBACK_4;
            break;
        case 5:
            var10000 = this.CGLIB$CALLBACK_5;
            break;
        default:
            var10000 = null;
        }

        return (Callback)var10000;
    }

    public void setCallback(int var1, Callback var2) {
        switch(var1) {
        case 0:
            this.CGLIB$CALLBACK_0 = (NoOp)var2;
            break;
        case 1:
            this.CGLIB$CALLBACK_1 = (MethodInterceptor)var2;
            break;
        case 2:
            this.CGLIB$CALLBACK_2 = (LazyLoader)var2;
            break;
        case 3:
            this.CGLIB$CALLBACK_3 = (InvocationHandler)var2;
            break;
        case 4:
            this.CGLIB$CALLBACK_4 = (FixedValue)var2;
            break;
        case 5:
            this.CGLIB$CALLBACK_5 = (Dispatcher)var2;
        }

    }

    public Callback[] getCallbacks() {
        CGLIB$BIND_CALLBACKS(this);
        return new Callback[]{this.CGLIB$CALLBACK_0, this.CGLIB$CALLBACK_1, this.CGLIB$CALLBACK_2, this.CGLIB$CALLBACK_3, this.CGLIB$CALLBACK_4, this.CGLIB$CALLBACK_5};
    }

    public void setCallbacks(Callback[] var1) {
        this.CGLIB$CALLBACK_0 = (NoOp)var1[0];
        this.CGLIB$CALLBACK_1 = (MethodInterceptor)var1[1];
        this.CGLIB$CALLBACK_2 = (LazyLoader)var1[2];
        this.CGLIB$CALLBACK_3 = (InvocationHandler)var1[3];
        this.CGLIB$CALLBACK_4 = (FixedValue)var1[4];
        this.CGLIB$CALLBACK_5 = (Dispatcher)var1[5];
    }

    static {
        CGLIB$STATICHOOK1();
    }
}

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