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Java中Cglib代理類重寫邏輯詳解

 更新時(shí)間：2023年11月27日 09:38:01   作者：ps酷教程  
這篇文章主要介紹了Java中Cglib代理類重寫邏輯詳解,代理類中只會(huì)維護(hù)NoOp這個(gè)回調(diào)屬性,并不會(huì)生成目標(biāo)類MyService中的noOp所對(duì)應(yīng)的方法,需要的朋友可以參考下

前言

要看懂Spring Aop，必須先看懂不同cglib回調(diào)類型所應(yīng)用的方法，在代理類中的重寫邏輯。

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回調(diào)

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

目標(biāo)類

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();

    }
}

結(jié)論

NoOp

代理類中只會(huì)維護(hù)NoOp這個(gè)回調(diào)屬性，并不會(huì)生成目標(biāo)類MyService中的noOp所對(duì)應(yīng)的方法

MethodInterceptor

可見，代理類中生成了目標(biāo)類MyService中的methodInterceptor方法所對(duì)應(yīng)的 CGLIB$methodInterceptor$1 和 methodInterceptor方法 這種類型的回調(diào)最為常用，它里面利用了FastClass，這種FastClass建立了調(diào)用邏輯和方法簽名和索引之間的映射關(guān)系，能夠快速的根據(jù)索引找到所對(duì)應(yīng)的調(diào)用邏輯。

final void CGLIB$methodInterceptor$1() {
	 // 直接調(diào)用父類的methodInterceptor方法 
     super.methodInterceptor();
 }

public final void methodInterceptor() {

	// 獲取綁定的回調(diào)對(duì)象
    MethodInterceptor var10000 = this.CGLIB$CALLBACK_1;
    
    if (var10000 == null) {
        CGLIB$BIND_CALLBACKS(this);
        var10000 = this.CGLIB$CALLBACK_1;
    }
	
	// 如果有設(shè)置的話(框架里面一般都設(shè)置了)
    if (var10000 != null) {
    
    	// 第一個(gè)參數(shù)就是當(dāng)前代理類對(duì)象this
    	// 第二個(gè)參數(shù)是MyService的methodInterceptor方法
    	// 第三個(gè)參數(shù)是參數(shù)，因?yàn)檫@個(gè)方法沒有參數(shù)，就用固定的這個(gè)CGLIB$emptyArgs，如果有參數(shù)的話，就會(huì)傳入方法的參數(shù)
   		// 最后一個(gè)參數(shù)是MethodProxy類型的，它與FastClass機(jī)制的使用相關(guān)
        var10000.intercept(this, CGLIB$methodInterceptor$1$Method, CGLIB$emptyArgs, CGLIB$methodInterceptor$1$Proxy);
    } else {
        super.methodInterceptor();
    }
}

LazyLoader

可見，代理類中生成了目標(biāo)類MyService中的lazyLoader方法所對(duì)應(yīng)的 lazyLoader 方法

public final void lazyLoader() {
    // 每次都會(huì)調(diào)用下面這個(gè)CGLIB$LOAD_PRIVATE_2()方法
    ((MyService)this.CGLIB$LOAD_PRIVATE_2()).lazyLoader();
}

private final synchronized Object CGLIB$LOAD_PRIVATE_2() {
	// 獲取CGLIB$LAZY_LOADER_2屬性，即綁定的回調(diào)對(duì)象
    Object var10000 = this.CGLIB$LAZY_LOADER_2;

	// 如果從CGLIB$LAZY_LOADER_2屬性獲取的是null，則走下面邏輯
	// 如果不為null，直接將結(jié)果返回，所以這種類型會(huì)將結(jié)果返回并保存，
	// 等下次調(diào)用，直接返回結(jié)果
	// 也就是說(shuō)這種類型的回調(diào)對(duì)象只會(huì)被調(diào)用 1 次
    if (var10000 == null) {
        // 如果還未綁定
        LazyLoader var10001 = this.CGLIB$CALLBACK_2;
        if (var10001 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10001 = this.CGLIB$CALLBACK_2;
        }
        // 調(diào)用回調(diào)對(duì)象的loadObject方法，
        //     并將調(diào)用結(jié)果返回作為方法的返回值
        //     并將返回的結(jié)果設(shè)置給this.CGLIB$LAZY_LOADER_2屬性
        var10000 = this.CGLIB$LAZY_LOADER_2 = var10001.loadObject();
    }
    
    // 返回調(diào)用結(jié)果或直接返回
    return var10000;
}

InvocationHandler

public final void invocationHandler() {
    try {
    	// 獲取綁定的回調(diào)對(duì)象CGLIB$CALLBACK_3
        InvocationHandler var10000 = this.CGLIB$CALLBACK_3;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_3;
        }
		// 直接調(diào)用回調(diào)對(duì)象的invoke方法，參數(shù)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() {

	 // 獲取綁定的回調(diào)對(duì)象
     FixedValue var10000 = this.CGLIB$CALLBACK_4;
     
     if (var10000 == null) {
     	 // 如果還未綁定
         CGLIB$BIND_CALLBACKS(this);
         var10000 = this.CGLIB$CALLBACK_4;
     }
     
	 // 每次調(diào)用都會(huì)調(diào)用回調(diào)對(duì)象的loadObject方法
     var10000.loadObject();
 }

Dispatcher

public final void dispatcher() {
	
	// 獲取綁定的回調(diào)對(duì)象
    Dispatcher var10000 = this.CGLIB$CALLBACK_5;
    
    if (var10000 == null) {
        CGLIB$BIND_CALLBACKS(this);
        var10000 = this.CGLIB$CALLBACK_5;
    }
    
    // 調(diào)用回調(diào)對(duì)象的loadObject方法，將返回的結(jié)果去調(diào)用dispatcher方法
    ((MyService)var10000.loadObject()).dispatcher();
}

[Cglib生成的代理類]

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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