從動態代理實現到Spring AOP看這一篇就夠了

時間 2019-12-07

標籤動態代理實現 spring aop 看這一篇夠了欄目 Spring 简体版

原文原文鏈接

代理是一種設計模式，目的是對外提供統一的接口（這樣能夠隱藏被代理類不想公開的方法），在此基礎上，能夠在代理類實現邏輯中加入一些附加操做，作一些加強處理，該方式不會影響被代理類的原實現。java

代理分爲靜態代理和動態代理兩種，靜態代理就是在代理類內部持有被代理對象的引用，這種方式很直接，但須要hard coding，不易擴展，沒法作統一處理。設計模式

動態代理主要有jdk提供的Proxy、Cglib以及Javassist，其中Javassist主要是一套字節碼操做庫，有兩種使用方式，既能夠有相似Cglib的用法，也能夠根據字節碼結構去動態生成類，本文主要講述Proxy和Cglib。緩存

動態代理在Spring、Mybatis、Dubbo等各大框架中均有大量使用，所以熟悉動態代理是閱讀這些框架源碼必須掌握的基本功之一bash

Proxy是根據接口生成代理類，生成的代理類實現了被代理類的接口，Cglib是生成被代理類的子類，所以被代理類不能爲final，並且必須有無參構造函數。app

Proxy

Proxy須要寫一個實現InvocationHandler（實現invoke方法）的代理類（如下稱Agency），注意Agency不是最後生成的動態代理類，動態代理類是Proxy.newProxyInstance過程當中生成的，newProxyInstance方法會爲動態代理類newInstance一個實例對象，動態代理類的主要思想是調用agency 對象（Agency類的實例）的invoke方法，在invoke方法中再經過反射調用被代理對象的方法，增長附加處理。
上代碼：框架

interface Subject {
    void doSomething();
}

interface DupSubject {
    void doSomethingAgain();
}

class Real implements Subject, DupSubject {
    public void doSomething() {
        System.out.println("=========Real doSomething=========");
    }

    @Override
    public void doSomethingAgain() {
        System.out.println("=========Real doSomethingAgain=========");
    }
}

class Agency implements InvocationHandler {
    private Real sub;

    public Object bind(Real sub) {
        this.sub = sub;
        Object obj = Proxy.newProxyInstance(Test.class.getClassLoader(), sub.getClass().getInterfaces(), this);
        return obj;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        // 前置加強處理
        System.out.println("+++++++++Agency begin+++++++");
        method.invoke(sub, args);
        // 後置加強處理
        System.out.println("+++++++++Agency end+++++++");
        return null;
    }
}

public class Test {
    public static void main(String[] args) {
        // 設置系統參數，輸出動態生成的代理類
        System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");
        Agency agency = new Agency();
        Real real = new Real();
        // 綁定被代理對象，返回代理對象
        Object obj = agency.bind(real);
        Subject sub = (Subject) (obj);
        sub.doSomething();
        DupSubject dubSub = (DupSubject) (obj);
        dubSub.doSomethingAgain();
    }
}
複製代碼

程序輸出內容爲：ide

+++++++++Agency begin+++++++
=========Real doSomething=========
+++++++++Agency end+++++++
+++++++++Agency begin+++++++
=========Real doSomethingAgain=========
+++++++++Agency end+++++++
複製代碼

上生成的動態代理類：函數

// 默認繼承Proxy類且實現被代理類的全部接口
final class $Proxy0 extends Proxy implements Subject, DupSubject {
    private static Method m1;
    private static Method m3;
    private static Method m2;
    private static Method m4;
    private static Method m0;
    
    // 將全部method對象在初始加載代理類時緩存下來，防止每次都經過反射獲取
    static {
        try {
            m3 = Class.forName("Subject").getMethod("doSomething", new Class[0]);
            m4 = Class.forName("DupSubject").getMethod("doSomethingAgain", new Class[0]);
            // 省略toString/equals/hashcode等方法
            ...
        } catch (NoSuchMethodException nosuchmethodexception) {
            throw new NoSuchMethodError(nosuchmethodexception.getMessage());
        } catch (ClassNotFoundException classnotfoundexception) {
            throw new NoClassDefFoundError(classnotfoundexception.getMessage());
        }
    }

    public $Proxy0(InvocationHandler invocationhandler) {
        // 向super類也就是proxy類傳入InvocationHandler對象
        super(invocationhandler);
    }
    
    // 直接調用了以前傳入的InvocationHandler對象的invoke方法
    public final void doSomething() {
        try {
            super.h.invoke(this, m3, null);
            return;
        } catch (Error) {
        } catch (Throwable throwable) {
            throw new UndeclaredThrowableException(throwable);
        }
    }
    
    // 直接調用了以前傳入的InvocationHandler對象的invoke方法
    public final void doSomethingAgain() {
        try {
            super.h.invoke(this, m4, null);
            return;
        } catch (Error) {
        } catch (Throwable throwable) {
            throw new UndeclaredThrowableException(throwable);
        }
    }
}
複製代碼

動態代理類是如何生成的具體參照ProxyGenerator的 generateClassFile方法，該方法先爲代理類添加equals/hashcode/toString方法，而後增長被代理類接口的全部方法，處理過程主要爲經過反射獲取被代理方法的方法名、參數類型、返回值類型、異常類型，而後生成根據以上參數生成代理方法的字節碼內容（字節碼實現一個事：即調用屬性InvocationHandler對象的invoke方法），看這個方法能夠充分理解class文件的組成，即常量池、字段表、方法表等。優化

注意：proxy方法之間的內部調用是不走invoke邏輯的ui

Cglib

上代碼：

interface Subject {
    void doSomething();
}

interface AnotherSubject {
    void doSomethingAgain();
}

class Real implements Subject, AnotherSubject {
    @Override
    public void doSomething() {
        System.out.println("=========Real doSomething=========");
    }

    @Override
    public void doSomethingAgain() {
        System.out.println("=========Real doSomethingAgain begin====");
        // 調用內部方法，注意invokeSuper時該調用是否會進入加強邏輯
        this.doSomething();
        System.out.println("=========Real doSomethingAgain end====");
    }
}

class Agency implements MethodInterceptor {
    private Object target;
    
    // 持有被代理對象
    public Agency(Object target) {
        this.target = target;
    }

    @Override
    // obj對象爲動態代理類的實例
    // method爲被代理類的方法
    // methodProxy持有被代理方法、代理方法、被代理類、代理類以及方法的index索引
    public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
        System.out.println("+++++++++Agency begin+++++++");
        // 直接調用被代理對象的方法
        method.invoke(target, args);
        // 調用methodProxy的invokeSuper方法，注意若是調用methodProxy的invoke方法
        // 由於傳入的obj爲動態代理對象，則會陷入死循環，若是爲被代理對象target，則不會
        proxy.invokeSuper(obj, args);
        System.out.println("+++++++++Agency end+++++++");
        return null;
    }
}

public class Test {
    public static void main(String[] args) {
        // 設置系統參數，輸出動態生成的代理類
        System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "E:/temp/dymamicCode");
        Real real = new Real();
        Agency agency = new Agency(real);
        Enhancer enhancer = new Enhancer();
        // 設置被代理類
        enhancer.setSuperclass(real.getClass());
        // 設置回調MethodInterceptor對象
        enhancer.setCallback(agency);
        Real proxy = (Real)enhancer.create();
        proxy.doSomething();
        proxy.doSomethingAgain();
    }
}
複製代碼

程序輸出結果爲：

+++++++++Agency begin+++++++
=========Real doSomething=========
=========Real doSomething=========
+++++++++Agency end+++++++

+++++++++Agency begin+++++++
// method.invoke 內容 begin
=========Real doSomethingAgain begin====
=========Real doSomething=========
=========Real doSomethingAgain end====
// method.invoke 內容 end
// methodProxy invokeSuper 內容 begin
=========Real doSomethingAgain begin====
// 傳入的obj是動態代理類實例，所以內部調用的this爲動態代理類實例，進入加強邏輯
+++++++++Agency begin+++++++
=========Real doSomething=========
=========Real doSomething=========
+++++++++Agency end+++++++
=========Real doSomethingAgain end====
// methodProxy invokeSuper 內容 end
+++++++++Agency end+++++++
複製代碼

上生成的動態代理類，主要有三個類，在生成fastclass過程當中還有一些附加類:

Real$$EnhancerByCGLIB$$148ae4e.class

// 默認實現Factory接口，繼承被代理類
public class Real$$EnhancerByCGLIB$$148ae4e extends Real 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;
    // MethodInterceptor對象，即callback
    private MethodInterceptor CGLIB$CALLBACK_0;
    // 樣例沒有實現filter，經過filter去過濾callback
    private static Object CGLIB$CALLBACK_FILTER;
    private static final Method CGLIB$doSomething$0$Method;
    private static final MethodProxy CGLIB$doSomething$0$Proxy;
    private static final Object[] CGLIB$emptyArgs;
    private static final Method CGLIB$doSomethingAgain$1$Method;
    private static final MethodProxy CGLIB$doSomethingAgain$1$Proxy;
    // 略去equals/hashcode等方法
    ...
    
    // 爲了方便閱讀，將該static塊提早
    static {
        CGLIB$STATICHOOK1();
    }
    
    static void CGLIB$STATICHOOK1() {
        CGLIB$THREAD_CALLBACKS = new ThreadLocal();
        CGLIB$emptyArgs = new Object[0];
        // var0爲代理類
        Class var0 = Class.forName("Real$$EnhancerByCGLIB$$148ae4e");
        // var1爲被代理類
        Class var1;
        // var10000持有全部的被代理方法
        Method[] var10000 = ReflectUtils.findMethods(new String[]{"doSomething", "()V", "doSomethingAgain", "()V"}, (var1 = Class.forName("Real")).getDeclaredMethods());
        // CGLIB$doSomething$0$Method爲被代理方法doSomething
        CGLIB$doSomething$0$Method = var10000[0];
        // doSomething的MethodProxy
        CGLIB$doSomething$0$Proxy = MethodProxy.create(var1, var0, "()V", "doSomething", "CGLIB$doSomething$0");
        CGLIB$doSomethingAgain$1$Method = var10000[1];
        CGLIB$doSomethingAgain$1$Proxy = MethodProxy.create(var1, var0, "()V", "doSomethingAgain", "CGLIB$doSomethingAgain$1");
        // 略去equals/hashcode等方法
        ...
    }
    
    final void CGLIB$doSomething$0() {
        super.doSomething();
    }
    
    // 代理方法doSomething調用入口
    public final void doSomething() {
        // CGLIB$CALLBACK_0爲MethodInterceptor對象
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (this.CGLIB$CALLBACK_0 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            // 調用MethodInterceptor對象的intercept方法
            // 重點看下調用傳參：
            // this爲代理對象實例，即Real$$EnhancerByCGLIB$$148ae4e類的實例
            // CGLIB$doSomething$0$Method爲被代理方法doSomething
            // CGLIB$emptyArgs 無參
            // CGLIB$doSomething$0$Proxy爲doSomething的methodProxy
            var10000.intercept(this, CGLIB$doSomething$0$Method, CGLIB$emptyArgs, CGLIB$doSomething$0$Proxy);
        } else {
            super.doSomething();
        }
    }

    final void CGLIB$doSomethingAgain$1() {
        super.doSomethingAgain();
    }
    
    // 代理方法doSomethingAgain調用入口
    public final void doSomethingAgain() {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (this.CGLIB$CALLBACK_0 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            // 參數分析同上
            var10000.intercept(this, CGLIB$doSomethingAgain$1$Method, CGLIB$emptyArgs, CGLIB$doSomethingAgain$1$Proxy);
        } else {
            super.doSomethingAgain();
        }
    }
    
    // 略去equals/hashcode等方法
   ...

    public static MethodProxy CGLIB$findMethodProxy(Signature var0) {
        String var10000 = var0.toString();
        switch(var10000.hashCode()) {
        case 516651364:
            if (var10000.equals("doSomethingAgain()V")) {
                return CGLIB$doSomethingAgain$1$Proxy;
            }
            break;
        // 略去equals/hashcode等方法    
        ...
        case 2121560294:
            if (var10000.equals("doSomething()V")) {
                return CGLIB$doSomething$0$Proxy;
            }
        }

        return null;
    }

    public Real$$EnhancerByCGLIB$$148ae4e() {
        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;
    }
    
    // 設置屬性CGLIB$CALLBACK_0，即MethodInterceptor對象
    private static final void CGLIB$BIND_CALLBACKS(Object var0) {
        Real$$EnhancerByCGLIB$$148ae4e var1 = (Real$$EnhancerByCGLIB$$148ae4e)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];
        }

    }
    
    // 生成被代理類實例
    public Object newInstance(Callback[] var1) {
        // 設置MethodInterceptor對象
        CGLIB$SET_THREAD_CALLBACKS(var1);
        Real$$EnhancerByCGLIB$$148ae4e var10000 = new Real$$EnhancerByCGLIB$$148ae4e();
        CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
        return var10000;
    }
    
    public Object newInstance(Callback var1) {
        CGLIB$SET_THREAD_CALLBACKS(new Callback[]{var1});
        Real$$EnhancerByCGLIB$$148ae4e var10000 = new Real$$EnhancerByCGLIB$$148ae4e();
        CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
        return var10000;
    }

    public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) {
        CGLIB$SET_THREAD_CALLBACKS(var3);
        Real$$EnhancerByCGLIB$$148ae4e var10000 = new Real$$EnhancerByCGLIB$$148ae4e;
        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];
    }
}

複製代碼

生成上述class的方式可見Enhancer的generateClass方法
由上可見，最終調用methodInterceptor的intercept方法，該方法中進行加強處理，而後調用被代理對象的相關方法，兩種方式：

method.invoke
methodProxy.invokeSuper
method.invoke就是直接調用被代理方法，重點看看methodProxy的invokeSuper和invoke會發生什麼？

public Object invokeSuper(Object obj, Object[] args) throws Throwable {
    try {
        // 初始化fastClass信息
        this.init();
        MethodProxy.FastClassInfo fci = this.fastClassInfo;
        // obj爲動態代理對象 f2爲代理類的fastClass 
        // i2爲該方法在fastClass的index
        return fci.f2.invoke(fci.i2, obj, args);
    ...
}
public Object invoke(Object obj, Object[] args) throws Throwable {
    try {
        this.init();
        MethodProxy.FastClassInfo fci = this.fastClassInfo;
        // obj爲被代理對象 f1爲被代理類的fastClass 
        // i1爲該方法在fastClass的index
        return fci.f1.invoke(fci.i1, obj, args);
    ...
}
複製代碼

都調用了init方法，該方法會初始化fastClassInfo，看看生成的fastClass的格式：

// 爲被代理類生成的FastClass
public class Real$$FastClassByCGLIB$$26cdbe extends FastClass {
    public Real$$FastClassByCGLIB$$26cdbe(Class var1) {
        super(var1);
    }
    
    // 根據方法 name和desc獲取index
    public int getIndex(Signature var1) {
        String var10000 = var1.toString();
        switch(var10000.hashCode()) {
        case 516651364:
            if (var10000.equals("doSomethingAgain()V")) {
                return 1;
            }
            break;
        ...    
        case 2121560294:
            if (var10000.equals("doSomething()V")) {
                return 0;
            }
        }

        return -1;
    }

    public int getIndex(String var1, Class[] var2) {
        switch(var1.hashCode()) {
        ...
        case -1265074063:
            if (var1.equals("doSomethingAgain")) {
                switch(var2.length) {
                case 0:
                    return 1;
                }
            }
            break;
        case 1794410543:
            if (var1.equals("doSomething")) {
                switch(var2.length) {
                case 0:
                    return 0;
                }
            }
        }

        return -1;
    }

    public int getIndex(Class[] var1) {
        switch(var1.length) {
        case 0:
            return 0;
        default:
            return -1;
        }
    }
    
    // 根據index var1調用被代理對象var2的方法
    public Object invoke(int var1, Object var2, Object[] var3) throws InvocationTargetException {
        Real var10000 = (Real)var2;
        int var10001 = var1;

        try {
            switch(var10001) {
            case 0:
                var10000.doSomething();
                return null;
            case 1:
                var10000.doSomethingAgain();
                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 {
        Real var10000 = new Real;
        Real 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 4;
    }
}

// 爲動態代理類生成的fastClass
public class Real$$EnhancerByCGLIB$$148ae4e$$FastClassByCGLIB$$1c2aeb82 extends FastClass {
    public Real$$EnhancerByCGLIB$$148ae4e$$FastClassByCGLIB$$1c2aeb82(Class var1) {
        super(var1);
    }

    public int getIndex(Signature var1) {
        String var10000 = var1.toString();
        switch(var10000.hashCode()) {
        case -2055565910:
            if (var10000.equals("CGLIB$SET_THREAD_CALLBACKS([Lnet/sf/cglib/proxy/Callback;)V")) {
                return 14;
            }
            break;
        case -1457535688:
            if (var10000.equals("CGLIB$STATICHOOK1()V")) {
                return 21;
            }
            break;
        case -894172689:
            if (var10000.equals("newInstance(Lnet/sf/cglib/proxy/Callback;)Ljava/lang/Object;")) {
                return 6;
            }
            break;
        case -713887907:
            if (var10000.equals("CGLIB$doSomething$0()V")) {
                return 22;
            }
            break;
        case -623122092:
            if (var10000.equals("CGLIB$findMethodProxy(Lnet/sf/cglib/core/Signature;)Lnet/sf/cglib/proxy/MethodProxy;")) {
                return 20;
            }
            break;
        case -419626537:
            if (var10000.equals("setCallbacks([Lnet/sf/cglib/proxy/Callback;)V")) {
                return 10;
            }
            break;
        case 516651364:
            if (var10000.equals("doSomethingAgain()V")) {
                return 9;
            }
            break;
        case 560567118:
            if (var10000.equals("setCallback(ILnet/sf/cglib/proxy/Callback;)V")) {
                return 7;
            }
            break;
        case 811063227:
            if (var10000.equals("newInstance([Ljava/lang/Class;[Ljava/lang/Object;[Lnet/sf/cglib/proxy/Callback;)Ljava/lang/Object;")) {
                return 4;
            }
            break;
        case 973717575:
            if (var10000.equals("getCallbacks()[Lnet/sf/cglib/proxy/Callback;")) {
                return 12;
            }
            break;
        case 1132140820:
            if (var10000.equals("CGLIB$doSomethingAgain$1()V")) {
                return 15;
            }
            break;
        case 1221173700:
            if (var10000.equals("newInstance([Lnet/sf/cglib/proxy/Callback;)Ljava/lang/Object;")) {
                return 5;
            }
            break;
        case 1230699260:
            if (var10000.equals("getCallback(I)Lnet/sf/cglib/proxy/Callback;")) {
                return 11;
            }
            break;
        case 1584330438:
            if (var10000.equals("CGLIB$SET_STATIC_CALLBACKS([Lnet/sf/cglib/proxy/Callback;)V")) {
                return 13;
            }
            break;
        case 2121560294:
            if (var10000.equals("doSomething()V")) {
                return 8;
            }
        ...    
        }

        return -1;
    }
    
    // 根據方法name和desc獲取index
    public int getIndex(String var1, Class[] var2) {
        switch(var1.hashCode()) {
        case -1549500735:
            if (var1.equals("CGLIB$doSomethingAgain$1")) {
                switch(var2.length) {
                case 0:
                    return 15;
                }
            }
            break;
        case -1265074063:
            if (var1.equals("doSomethingAgain")) {
                switch(var2.length) {
                case 0:
                    return 9;
                }
            }
            break;
        case -1053468136:
            if (var1.equals("getCallbacks")) {
                switch(var2.length) {
                case 0:
                    return 12;
                }
            }
            break;
        case -60403779:
            if (var1.equals("CGLIB$SET_STATIC_CALLBACKS")) {
                switch(var2.length) {
                case 1:
                    if (var2[0].getName().equals("[Lnet.sf.cglib.proxy.Callback;")) {
                        return 13;
                    }
                }
            }
            break;
        case 85179481:
            if (var1.equals("CGLIB$SET_THREAD_CALLBACKS")) {
                switch(var2.length) {
                case 1:
                    if (var2[0].getName().equals("[Lnet.sf.cglib.proxy.Callback;")) {
                        return 14;
                    }
                }
            }
            break;
        case 161998109:
            if (var1.equals("CGLIB$STATICHOOK1")) {
                switch(var2.length) {
                case 0:
                    return 21;
                }
            }
            break;
        case 180909336:
            if (var1.equals("CGLIB$doSomething$0")) {
                switch(var2.length) {
                case 0:
                    return 22;
                }
            }
            break;
        case 495524492:
            if (var1.equals("setCallbacks")) {
                switch(var2.length) {
                case 1:
                    if (var2[0].getName().equals("[Lnet.sf.cglib.proxy.Callback;")) {
                        return 10;
                    }
                }
            }
            break;
        case 1154623345:
            if (var1.equals("CGLIB$findMethodProxy")) {
                switch(var2.length) {
                case 1:
                    if (var2[0].getName().equals("net.sf.cglib.core.Signature")) {
                        return 20;
                    }
                }
            }
            break;
        case 1794410543:
            if (var1.equals("doSomething")) {
                switch(var2.length) {
                case 0:
                    return 8;
                }
            }
            break;
        case 1811874389:
            if (var1.equals("newInstance")) {
                switch(var2.length) {
                case 1:
                    String var10001 = var2[0].getName();
                    switch(var10001.hashCode()) {
                    case -845341380:
                        if (var10001.equals("net.sf.cglib.proxy.Callback")) {
                            return 6;
                        }
                        break;
                    case 1730110032:
                        if (var10001.equals("[Lnet.sf.cglib.proxy.Callback;")) {
                            return 5;
                        }
                    }
                case 2:
                default:
                    break;
                case 3:
                    if (var2[0].getName().equals("[Ljava.lang.Class;") && var2[1].getName().equals("[Ljava.lang.Object;") && var2[2].getName().equals("[Lnet.sf.cglib.proxy.Callback;")) {
                        return 4;
                    }
                }
            }
            break;
        case 1817099975:
            if (var1.equals("setCallback")) {
                switch(var2.length) {
                case 2:
                    if (var2[0].getName().equals("int") && var2[1].getName().equals("net.sf.cglib.proxy.Callback")) {
                        return 7;
                    }
                }
            }
            break;
        case 1905679803:
            if (var1.equals("getCallback")) {
                switch(var2.length) {
                case 1:
                    if (var2[0].getName().equals("int")) {
                        return 11;
                    }
                }
            }
            break;
        ...

        return -1;
    }

    public int getIndex(Class[] var1) {
        switch(var1.length) {
        case 0:
            return 0;
        default:
            return -1;
        }
    }
    
    // 根據index var1調用代理對象var2的方法
    public Object invoke(int var1, Object var2, Object[] var3) throws InvocationTargetException {
        148ae4e var10000 = (148ae4e)var2;
        int var10001 = var1;

        try {
            switch(var10001) {
            ...
            case 4:
                return var10000.newInstance((Class[])var3[0], (Object[])var3[1], (Callback[])var3[2]);
            case 5:
                return var10000.newInstance((Callback[])var3[0]);
            case 6:
                return var10000.newInstance((Callback)var3[0]);
            case 7:
                var10000.setCallback(((Number)var3[0]).intValue(), (Callback)var3[1]);
                return null;
            case 8:
                // 調用代理對象的doSomething方法
                var10000.doSomething();
                return null;
            case 9:
                // 調用代理對象的doSomethingAgain方法
                var10000.doSomethingAgain();
                return null;
            case 10:
                var10000.setCallbacks((Callback[])var3[0]);
                return null;
            case 11:
                return var10000.getCallback(((Number)var3[0]).intValue());
            case 12:
                return var10000.getCallbacks();
            case 13:
                148ae4e.CGLIB$SET_STATIC_CALLBACKS((Callback[])var3[0]);
                return null;
            case 14:
                148ae4e.CGLIB$SET_THREAD_CALLBACKS((Callback[])var3[0]);
                return null;
            case 15:
                var10000.CGLIB$doSomethingAgain$1();
                return null;
            ...
            case 20:
                return 148ae4e.CGLIB$findMethodProxy((Signature)var3[0]);
            case 21:
                148ae4e.CGLIB$STATICHOOK1();
                return null;
            case 22:
                var10000.CGLIB$doSomething$0();
                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 {
        148ae4e var10000 = new 148ae4e;
        148ae4e 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 22;
    }
}
複製代碼

fastClass機制是爲了加快執行速度、減小運行時反射，經過上述代碼分析，能夠明確method.invoke和methodProxy.invokeSuper的區別

Spring的動態代理是怎麼玩的

Spring Aop及周邊框架大量用到動態代理，在Spring中經過註解使用Aop：

@Configuration
@Aspect
public class AopTest {
    @Pointcut("execution(* com.example.demo.controller.*.*(..))")
    public void pointCut() {
        System.out.println("This is a pointcut");
    }

    @Before("pointCut()")
    public void begin() {
        System.out.println("Pointcut begin");
    }

    @After("pointCut()")
    public void after() {
        System.out.println("Pointcut end");
    }
}
@Configuration
@Aspect
public class AopAnotherTest {
    @Pointcut("execution(* com.example.demo.controller.*.*(..))")
    public void pointAnotherCut() {
        System.out.println("This is a another pointcut");
    }

    @Before("pointAnotherCut()")
    public void begin() {
        System.out.println("Another pointcut begin");
    }

    @After("pointAnotherCut()")
    public void after() {
        System.out.println("Another pointcut end");
    }
}
@RestController
public class AopController implements Datasource {
    @RequestMapping(path = "/aop/test", method = RequestMethod.GET)
    public ResponseEntity testAop() {
        System.out.println("testAop");
        return ResponseEntity.ok().body(null);
    }
}
複製代碼

除了上述代碼外，還須要在啓動類添加註解@EnableAspectJAutoProxy
之因此設置兩個切面，主要是想說明Spring是對全部切面進行統一處理，而不是每一個單獨處理一次，執行結果以下：

Another pointcut begin
Pointcut begin
testAop
Pointcut end
Another pointcut end  
複製代碼

Spring在bean初始化以前經過beanPostProcessor機制建立代理類，具體流程見圖：

其中getAdvisors部分會將該bean全部方法相關的advisor組織到一塊兒處理，以下:

// 將class的全部method過一遍
for (Method method : getAdvisorMethods(aspectClass)) {
    // 獲取method對應的Advisor
    Advisor advisor = getAdvisor(method, lazySingletonAspectInstanceFactory, advisors.size(), aspectName);
    if (advisor != null) {
    	advisors.add(advisor);
    }
}
複製代碼

JDK動態代理部分會獲取到該bean類的全部接口，而後附加一些SpringProxy的特有接口，調用Proxy生成動態代理類，重點看下Cglib處理，和以前的講述稍微有點不一樣

Cglib getProxy方法：

public Object getProxy(@Nullable ClassLoader classLoader) {
    ...
    // 獲取被代理類
    Class<?> rootClass = this.advised.getTargetClass();
    Assert.state(rootClass != null, "Target class must be available for creating a CGLIB proxy");
    
    Class<?> proxySuperClass = rootClass;
    // 若是該類已是cglib代理類
    if (ClassUtils.isCglibProxyClass(rootClass)) {
        // 獲取原被代理類，將要生成的動態代理類爲該類的子類
    	proxySuperClass = rootClass.getSuperclass();
    	Class<?>[] additionalInterfaces = rootClass.getInterfaces();
    	for (Class<?> additionalInterface : additionalInterfaces) {
    		this.advised.addInterface(additionalInterface);
    	}
    }
    ...
    
    // Configure CGLIB Enhancer...
    Enhancer enhancer = createEnhancer();
    if (classLoader != null) {
    	enhancer.setClassLoader(classLoader);
    	if (classLoader instanceof SmartClassLoader &&
    			((SmartClassLoader) classLoader).isClassReloadable(proxySuperClass)) {
    		enhancer.setUseCache(false);
    	}
    }
    // 生成的動態代理類爲原被代理類的子類
    enhancer.setSuperclass(proxySuperClass);
    // 獲取被代理類全部接口，附加SpringProxy特有接口
    enhancer.setInterfaces(AopProxyUtils.completeProxiedInterfaces(this.advised));
    enhancer.setNamingPolicy(SpringNamingPolicy.INSTANCE);
    enhancer.setStrategy(new ClassLoaderAwareUndeclaredThrowableStrategy(classLoader));
    
    // 重點關注callback邏輯
    Callback[] callbacks = getCallbacks(rootClass);
    Class<?>[] types = new Class<?>[callbacks.length];
    for (int x = 0; x < types.length; x++) {
    	types[x] = callbacks[x].getClass();
    }
    
    // callbackFilter的做用是根據條件過濾出調用的callback
    enhancer.setCallbackFilter(new ProxyCallbackFilter(
    	this.advised.getConfigurationOnlyCopy(), this.fixedInterceptorMap, this.fixedInterceptorOffset));
    enhancer.setCallbackTypes(types);
    
    // Generate the proxy class and create a proxy instance.
    return createProxyClassAndInstance(enhancer, callbacks);
複製代碼

重點看下getCallBacks：

private Callback[] getCallbacks(Class<?> rootClass) throws Exception {
	// 和EnableAspectJAutoProxy配置有關，是否將proxy暴露到上下文AopContext，默認爲false
	boolean exposeProxy = this.advised.isExposeProxy();
	// 動態代理配置是否不容許修改，和優化有關，默認爲false
	boolean isFrozen = this.advised.isFrozen();
	// 是否每次都返回同一個代理對象，也就是代理對象能夠被緩存，跟bean的生命週期有關
	boolean isStatic = this.advised.getTargetSource().isStatic();

	// Choose an "aop" interceptor (used for AOP calls).
	// 這個是重點，aop代理就走這個interceptor
	Callback aopInterceptor = new DynamicAdvisedInterceptor(this.advised);

	// Choose a "straight to target" interceptor. (used for calls that are
	// unadvised but can return this). May be required to expose the proxy.
	Callback targetInterceptor;
	if (exposeProxy) {
		targetInterceptor = isStatic ?
    		new StaticUnadvisedExposedInterceptor(this.advised.getTargetSource().getTarget()) :
    		new DynamicUnadvisedExposedInterceptor(this.advised.getTargetSource());
	}
	else {
		targetInterceptor = isStatic ?
            // 通常走這裏
    		new StaticUnadvisedInterceptor(this.advised.getTargetSource().getTarget()) :
    		new DynamicUnadvisedInterceptor(this.advised.getTargetSource());
	}

	// Choose a "direct to target" dispatcher (used for
	// unadvised calls to static targets that cannot return this).
	Callback targetDispatcher = isStatic ?
		new StaticDispatcher(this.advised.getTargetSource().getTarget()) : new SerializableNoOp();

	Callback[] mainCallbacks = new Callback[] {
		aopInterceptor,  // for normal advice
		targetInterceptor,  // invoke target without considering advice, if optimized
		new SerializableNoOp(),  // no override for methods mapped to this
		targetDispatcher, this.advisedDispatcher,
		new EqualsInterceptor(this.advised),
		new HashCodeInterceptor(this.advised)
	};
    ...
}
複製代碼

看下Aop相關的DynamicAdvisedInterceptor的intercept方法：

public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
	Object oldProxy = null;
	boolean setProxyContext = false;
	Object target = null;
	TargetSource targetSource = this.advised.getTargetSource();
	try {  
        ...  
    	target = targetSource.getTarget();  
    	Class<?> targetClass = (target != null ? target.getClass() : null);  
    	// 重點：將全部的MethodInterceptor串成一個鏈  
    	List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);  
    	Object retVal;
        ...
        // proxy爲動態代理後的bean
        // target爲原bean
        // proceed方法爲處理以前提到的chain上全部methodInterceptor
        // 最後一個methodinterceptor調用methodProxy的invoke方法
        // methodProxy.invoke(this.target, this.arguments);
    	retVal = new CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy).proceed();
		
    	retVal = processReturnType(proxy, target, method, retVal);
    	return retVal;
	}
	finally {
    	if (target != null && !targetSource.isStatic()) {
    	    targetSource.releaseTarget(target);
    	}
    	if (setProxyContext) {
    		// Restore old proxy.
    		AopContext.setCurrentProxy(oldProxy);
    	}
	}
}
複製代碼

全部的methodInterceptor組成chain，依次調用，最後一個methodinterceptor調用methodProxy的invoke方法：

methodProxy.invoke(this.target, this.arguments);
複製代碼

這裏的target爲原始bean，不會陷入死循環，和cglib的分析呼應。

看到這的都是愛鑽研的好同窗

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