java - What Guice MethodInterceptor should return -

i trying find answer should returned guice methodinterceptor. difference between returning methodinvocation.proceed(); , returning null;

here situation: in cases user has right invoke method in not. want implement kind situation using guice aop.

what should return if don't want invoke method? , difference between returning null , other object.

@retention(retentionpolicy.runtime) @target(elementtype.method) public @interface aopestablisher{  }  class guicemodule extends abstractmodule{      @override      protected void configure() {         guiceexampleaop guiceexampleaop = new guiceexampleaop ();        requestinjection(guiceexampleaop);        bindinterceptor(matchers.any(),    matchers.annotatedwith(aopestablisher.class),    guiceexampleaop );    } }   class commandexecutor{    @aopestablisher    public void executeinsomecases(){        //i want execute command in cases    } } 

and here interceptor class:

import org.aopalliance.intercept.methodinterceptor;  public class guiceexampleaop implements methodinterceptor {      @inject     user user;      @override     public object invoke(methodinvocation methodinvocation) throws throwable {              if(user.hasrigths(){                 return methodinvocation.proceed();             else{                 return null?                 return methodinvocation?                 //what should returned here?                 // difference between returning methodinvocation , null             }     } } 

thanks help.

what return result of method. if want prevent invocation, should either throw exception or return sort of "unauthorized" message. here.

if using java8+, i'd recommend best option change method signature return optional instead of whatever type, , return empty.