如何通过环绕构造函数替换类型的实例？

Question

I have a legacy lib that creates instances of BeanProxy . Unfortunately this implementation has a flaw I would like to fix. As I don't want to start working with patched libs, I wanted to create an Aspect wrapping the construction of BeanProxy and return an instance of my modified BeanProxy sub-type.

I created the following Aspect and it is correctly woven and called whenever a new instance of BeanProxy is created:

@Aspect
public class CWebBeanProxyInjectingAspect {

    @Pointcut("execution(public flex.messaging.io.BeanProxy.new(..))")
    void createBeanProxy() {}

    @Around("createBeanProxy()")
    public Object createAlternateBeanProxy(final ProceedingJoinPoint pjp) throws Throwable {
        System.out.println("createAlternateBeanProxy");
        final Object result = pjp.proceed();
        System.out.println(result);
        return result;
    }
}

Unfortunately result is always null ... what am I doing wrong? What do I have to change? I should mention, that I am using AspectJ LoadTimeWeaving and the spring-instrument-3.1.1.RELEASE.jar as agent.

Answer 1

Constructor execution don't return anything (is void ). If you want to return the created object, use call in your pointcut:

  @Pointcut("call(public flex.messaging.io.BeanProxy.new(..))")
    void createBeanProxy() {}

see Contstructor call and Constructor execution in http://www.eclipse.org/aspectj/doc/next/progguide/semantics-joinPoints.html