spring学习总结012 --- AOP基础之动态代理

spring AOP内部的原理是动态代理，spring AOP内部使用了两种代理方式：JDK动态代理和CGLIB动态代理

JDK动态代理

JDK动态代理最基本要素：接口、实现接口的类、实现了InvocationHandler接口的类、lang包下的Proxy类

public interface MyService {
    void func();
}

@Slf4j
public class MyServiceImpl implements MyService {

    @Override
    public void func() {
        log.info("Invoke func...");
    }
}

@Slf4j
public class JdkProxyInvocationHandler implements InvocationHandler {

    // 被代理对象
    private Object target;

    public JdkProxyInvocationHandler(Object target) {
        this.target = target;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        log.info("JdkProxyInvocationHandler [invoke]");
        return method.invoke(target, args);
    }
}

测试类：

public class Main1 {

    public static void main(String[] args) {

        // 输出代理类字节码到磁盘
        System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");
        MyService myService = new MyServiceImpl();
        InvocationHandler handler = new JdkProxyInvocationHandler(myService);
        MyService myServiceProxy = (MyService) Proxy.newProxyInstance(myService.getClass().getClassLoader(), myService.getClass().getInterfaces(), handler);
        myServiceProxy.func();
    }
}

运行结果：

频次很高的问题：为啥JDK代理，被代理类一定是接口实现类？原因就是JAVA的单继承限制，通过代理类字节码反编译结果就能看到；

JDK动态代理中生成的代理类实质上是实现了被代理类的接口，然后调用InvocationHandler接口的invoke方法实现增强和被代理类方法的执行；

public final class $Proxy0 extends Proxy implements MyService {
    private static Method m1;
    private static Method m2;
    private static Method m3;
    private static Method m0;

    public $Proxy0(InvocationHandler var1) throws  {
        super(var1);
    }

    public final boolean equals(Object var1) throws  {
        try {
            return (Boolean)super.h.invoke(this, m1, new Object[]{var1});
        } catch (RuntimeException | Error var3) {
            throw var3;
        } catch (Throwable var4) {
            throw new UndeclaredThrowableException(var4);
        }
    }

    public final String toString() throws  {
        try {
            return (String)super.h.invoke(this, m2, (Object[])null);
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

    public final void func() throws  {
        try {
            super.h.invoke(this, m3, (Object[])null);
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

    public final int hashCode() throws  {
        try {
            return (Integer)super.h.invoke(this, m0, (Object[])null);
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

    static {
        try {
            m1 = Class.forName("java.lang.Object").getMethod("equals", Class.forName("java.lang.Object"));
            m2 = Class.forName("java.lang.Object").getMethod("toString");
            m3 = Class.forName("com.demo.jdkproxy.MyService").getMethod("func");
            m0 = Class.forName("java.lang.Object").getMethod("hashCode");
        } catch (NoSuchMethodException var2) {
            throw new NoSuchMethodError(var2.getMessage());
        } catch (ClassNotFoundException var3) {
            throw new NoClassDefFoundError(var3.getMessage());
        }
    }
}

CGLIB动态代理

需要在项目中引入cglib包，CGLIB代理是基于继承的，原理是对代理的目标类生成一个子类，并复写其中的方法实现增强

@Slf4j
public class CglibService {

    public void func() {
        log.info("Invoke [CGlib] func.....");
    }
}

@Slf4j
public class CGlibMethodInterceptor implements MethodInterceptor {

    @Override
    public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
        log.info("[CGlibMethodInterceptor] intercept");
        return methodProxy.invokeSuper(o ,objects);
    }
}

测试类：

public class Main2 {
    public static void main(String[] args) {
        // 输出代理类字节码到文件
        System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "D:\\class");

        Enhancer enhancer = new Enhancer();

        enhancer.setSuperclass(CglibService.class);

        enhancer.setCallback(new CGlibMethodInterceptor());

        CglibService cglibServiceProxy = (CglibService) enhancer.create(); //创建代理类

        cglibServiceProxy.func();
    }
}

执行结果：

字节码反编译结果:

public class CglibService$$EnhancerByCGLIB$$4c82ace2 extends CglibService 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$func$0$Method;
    private static final MethodProxy CGLIB$func$0$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("com.demo.cglibproxy.CglibService$$EnhancerByCGLIB$$4c82ace2");
        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$5");
        CGLIB$func$0$Method = ReflectUtils.findMethods(new String[]{"func", "()V"}, (var1 = Class.forName("com.demo.cglibproxy.CglibService")).getDeclaredMethods())[0];
        CGLIB$func$0$Proxy = MethodProxy.create(var1, var0, "()V", "func", "CGLIB$func$0");
    }

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

    public final void func() {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

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

    final void CGLIB$finalize$1() throws Throwable {
        super.finalize();
    }

    protected final void finalize() throws Throwable {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

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

    final boolean CGLIB$equals$2(Object var1) {
        return super.equals(var1);
    }

    public final boolean equals(Object var1) {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            Object var2 = var10000.intercept(this, CGLIB$equals$2$Method, new Object[]{var1}, CGLIB$equals$2$Proxy);
            return var2 == null ? false : (Boolean)var2;
        } else {
            return super.equals(var1);
        }
    }

    final String CGLIB$toString$3() {
        return super.toString();
    }

    public final String toString() {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        return var10000 != null ? (String)var10000.intercept(this, CGLIB$toString$3$Method, CGLIB$emptyArgs, CGLIB$toString$3$Proxy) : super.toString();
    }

    final int CGLIB$hashCode$4() {
        return super.hashCode();
    }

    public final int hashCode() {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            Object var1 = var10000.intercept(this, CGLIB$hashCode$4$Method, CGLIB$emptyArgs, CGLIB$hashCode$4$Proxy);
            return var1 == null ? 0 : ((Number)var1).intValue();
        } else {
            return super.hashCode();
        }
    }

    final Object CGLIB$clone$5() throws CloneNotSupportedException {
        return super.clone();
    }

    protected final Object clone() throws CloneNotSupportedException {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        return var10000 != null ? var10000.intercept(this, CGLIB$clone$5$Method, CGLIB$emptyArgs, CGLIB$clone$5$Proxy) : super.clone();
    }

    public static MethodProxy CGLIB$findMethodProxy(Signature var0) {
        String var10000 = var0.toString();
        switch(var10000.hashCode()) {
        case -1574182249:
            if (var10000.equals("finalize()V")) {
                return CGLIB$finalize$1$Proxy;
            }
            break;
        case -509717967:
            if (var10000.equals("func()V")) {
                return CGLIB$func$0$Proxy;
            }
            break;
        case -508378822:
            if (var10000.equals("clone()Ljava/lang/Object;")) {
                return CGLIB$clone$5$Proxy;
            }
            break;
        case 1826985398:
            if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
                return CGLIB$equals$2$Proxy;
            }
            break;
        case 1913648695:
            if (var10000.equals("toString()Ljava/lang/String;")) {
                return CGLIB$toString$3$Proxy;
            }
            break;
        case 1984935277:
            if (var10000.equals("hashCode()I")) {
                return CGLIB$hashCode$4$Proxy;
            }
        }

        return null;
    }

    public CglibService$$EnhancerByCGLIB$$4c82ace2() {
        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) {
        CglibService$$EnhancerByCGLIB$$4c82ace2 var1 = (CglibService$$EnhancerByCGLIB$$4c82ace2)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);
        CglibService$$EnhancerByCGLIB$$4c82ace2 var10000 = new CglibService$$EnhancerByCGLIB$$4c82ace2();
        CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
        return var10000;
    }

    public Object newInstance(Callback var1) {
        CGLIB$SET_THREAD_CALLBACKS(new Callback[]{var1});
        CglibService$$EnhancerByCGLIB$$4c82ace2 var10000 = new CglibService$$EnhancerByCGLIB$$4c82ace2();
        CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
        return var10000;
    }

    public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) {
        CGLIB$SET_THREAD_CALLBACKS(var3);
        CglibService$$EnhancerByCGLIB$$4c82ace2 var10000 = new CglibService$$EnhancerByCGLIB$$4c82ace2;
        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();
    }
}

二者简单比较

1、JDK动态代理是基于接口实现的，因此无法对接口中未定义的方法进行代理

2、CGLIB动态代理是基于继承的，因为代理类底层是个子类，因此无JDK动态代理的缺陷

3、CGLIB动态代理，无法对用final修饰的类进行代理