Intercepting all methods of an interface

[spgmx]

Hi,

I want to intercept all methods of an interface. OK, no problem - implement a MethodInterceptor - done.

But my interceptor should implement this interface too. How can I dispatch the methods of my adviced class to the methods of my interceptor?

interface Foo {
 Object method1(Object o, String s);
 void method2(Date d, int i);
}

class FooImpl implements Foo {
 Object method1(Object o, String s) {...}
 void method2(Date d, int i) {...}
}

class FooInterceptor implements MethodInterceptor, Foo {
 Object invoke(MethodInvocation methodinvocation) throws Throwable {
 // how can I dispatch here automatically to method1 and method2?
 }

 Object method1(Object o, String s) {...}
 void method2(Date d, int i) {...}

}

Thank you

[bdangubic]

Hi,

I want to intercept all methods of an interface. OK, no problem - implement a MethodInterceptor - done.

But my interceptor should implement this interface too. How can I dispatch the methods of my adviced class to the methods of my interceptor?

interface Foo {
 Object method1(Object o, String s);
 void method2(Date d, int i);
}

class FooImpl implements Foo {
 Object method1(Object o, String s) {...}
 void method2(Date d, int i) {...}
}

class FooInterceptor implements MethodInterceptor, Foo {
 Object invoke(MethodInvocation methodinvocation) throws Throwable {
 // how can I dispatch here automatically to method1 and method2?
 }

 Object method1(Object o, String s) {...}
 void method2(Date d, int i) {...}

}

Thank you

You are introducing recursion here that will never end... You are intercepting on Foo via interceptor that is also Foo. so you'll just keep recursing without an end in sight...

[spgmx]

My pointcut will be on FooImpl not on Foo.

[bdangubic]

My pointcut will be on FooImpl not on Foo.

why is the interceptor implementing Foo interface?

[spgmx]

Because it shall intercept every Foo method.

[bdangubic]

Because it shall intercept every Foo method.

just take it out, you just need to implement method interceptor. you'll setup what you are intercepting (Foo) through Spring.

[spgmx]

OK, I can do this, but the main question is still not answered:

How can I dispatch the methods of my adviced class to the methods of my interceptor?

if then else?

[Marten Deinum]

What is it that your interceptor should do?! Why create an implementation if the real implementation is your interceptor. I don't understand what you are trying to do.

[spgmx]

I want to inspect/manipulate the method arguments and then delegate to the impl class or reject the call.

But here is still a bug in my concept. This would lead to an endless loop...

Hm...

[Marten Deinum]

So then implement it that way... You are making it way to complex....

Your MethodInterceptor can do just that... Have you actually looked at the documentation of the MethodInterceptor and MethodInvocation class?!

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.springframework.aop.framework.ReflectiveMethodInvocation;


public class FooInterceptor implements MethodInterceptor {

	@Override
	public Object invoke(MethodInvocation invocation) throws Throwable {
		ReflectiveMethodInvocation method = (ReflectiveMethodInvocation) invocation;
		Object[] arguments = method.getArguments();
		//modify arguments
		method.setArguments(arguments);
		if (ok) {
			method.proceed();
		} else {
			return null; // or throw an exception
		}
	}

}

But why do it this way, using an AspectJ aspect would make it much easier.

@Aspect
public class FooInterceptor {

	@Pointcut("execution(* *..Foo+.*(..))")
	void fooMethods() {}
	
	@Around("fooMethods()")
	public Object intercept(ProceedingJoinPoint pjp) {
		Object[] arguments = pjp.getArgs();
		//change arguments
		if (ok) {
			pjp.proceed(arguments);
		} else {
			return null; // or throw an exception
		}
	}
}

Put it in your application context, include <aop:aspectj-autoproxy /> and presto...