覆盖时reflection.proxy无效 [英] reflection.proxy not valid when override

问题描述

当有覆盖方法时，reflection.proxy 似乎不是预期的.详细来说，从简单的应用开始:

It seems reflection.proxy does not what is expected when there are overriden methods. In detail, starting with simple application:

static void debug( String fmt, Object... args ) {
    System.out.println( String.format(fmt,args));
}

interface I {
    void m1();
    void m2();
}

static class A implements I {
    public void m1() { System.out.println( "A.m1" ); m2(); }
    public void m2() { System.out.println( "A.m2" ); }
}

static class B extends A {
    @Override
    public void m2() { System.out.println( "B.m2" ); }
}


public static void main( String[] args )
{
    B b = new B();
    b.m1();
}

输出如预期:

A.m1
B.m2

现在，我们尝试代理对B b"的所有方法的调用.添加以下新代码:

Now, we try to proxify the calls to all methods of "B b". Following new code is added:

static public class HelloInvocationHandler implements InvocationHandler {

    I proxied;

    HelloInvocationHandler( I proxied ) {
        this.proxied = proxied;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args)
            throws Throwable {

        String methodName = method.getName();
        debug( "HelloInvocationHandler: invoke method %s", methodName);
        return method.invoke(proxied,args);
    }
}

public static void main( String[] args )
{
    B b = new B();
    HelloInvocationHandler handler = new HelloInvocationHandler(b);
    I pb = (I) Proxy.newProxyInstance(
            I.class.getClassLoader(),
            new Class[] { I.class },
            handler);

    pb.m1();
}

新的输出是:

HelloInvocationHandler: invoke method m1
A.m1
B.m2

如您所见，对m2"的调用不会跨代理执行.如果对 B 的方法的所有调用都跨代理，则输出中应出现一行HelloInvocationHandler:invoke method m2".

as you can see, the call to "m2" is not executed accross the proxy. If all call to B's methods was accross the proxy, a line "HelloInvocationHandler: invoke method m2" should appear in the ouput.

有什么提示吗?

谢谢.

推荐答案

您可以使用 CGLib 库来创建代理.使用 Enhancer.create(B.class, new HelloInvocationHandler()) 来拦截方法调用.它并不比使用 JDK Proxy 难，但要灵活得多.应该对你的情况有所帮助.拦截器应该这样实现:

You can use CGLib library to create proxy. Use Enhancer.create(B.class, new HelloInvocationHandler()) to to intercept method invocations. It's not harder than using JDK Proxy, but much more flexible. Should help in your case. The interceptor should be implemented like this:

public class HelloInvocationHandler implements MethodInterceptor {

    public Object intercept(Object object, Method method, Object[] args,
         MethodProxy methodProxy) throws Throwable {
     debug( "HelloInvocationHandler: invoke method %s", method.getName());
     return methodProxy.invokeSuper(object, args);
    }
}

像这样使用它:

B pb = (B)Enhancer.create(B.class, new HelloInvocationHandler());
pb.m1();

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