question about business method interceptor

[vitesse wei]

mock question:
A developer writes an interceptor class called Foolnterceptor containing the following
Aroundlnvoke method:
11 . @Aroundlnvoke
12. public Object intercept(lnvocationContext ctx) {
13. return "intercepted";
14.}
Foolnterceptor is applied to a business method in a stateless session bean:
11. @lnterceptors(Foolnterceptor.class)
12. public String testzero(int i) {
13. return (i == 0)? "zero": "not zero";
14. }
Which describes the result when a client invokes the testzero method with a value of 1?
A. The intercept method is NEVER invoked.
B. The client receives a return value of "zero".
C. The client receives a return value of "not zero".
D. The client receives a return value of "intercepted".

given answer is D,why business method returns value from interceptor method according given answer?I think it's C,when business method was called,it's interceptor method will run too,but how can business method get return value from interceptor method?anyone clear this for me,thanks.

[Adam Tkaczyk]

It is very simple.
When you call business method which have interceptor only interceptor is called (from client view) and some informations about this method is given in InvocationContext object.

If you want to return value from business method you should write following code in your interceptor method

@Aroundlnvoke
public Object intercept(lnvocationContext ctx) {
try{
return ctx.proceed();
}catch(Exception e){...}
return null;
}
or another way

@Aroundlnvoke
public Object intercept(lnvocationContext ctx) {
try{
return ctx.getMethod().invoke(ctx.getTarget(),ctx.getParameters());
}catch(java.lang.reflect.InvocationTargetException e){...}
return null;
}