# Simplest Possible EJB 3.1 Interceptor

public class CallTracer {
    @AroundInvoke
    public Object transformReturn(InvocationContext context) throws Exception{
        System.out.println("---" + context.getMethod());
        return context.proceed();
    }
}

You can apply the interceptor now on the EJB class or its methods. The simplest way is to use annotations - but you can use XML as well.

@Stateless
@Interceptors(CallTracer.class)
public class HelloBean{
    public String sayHello(String message) {
        return "Echo from bean: " + message;
    }
}


How to compile:You will need the the EJB 3.0 / 3.1 API in the classpath, or at least the @Interceptor annotation.How to deploy: Just JAR or WAR the interceptor with an EJB and put the archive into e.g: [glassfishv3]\glassfish\domains\domain1\autodeploy
Btw. the deployment of the WAR took on my machine:

INFO: Loading application LeanestInterceptor at /LeanestInterceptor
INFO: Deployment of LeanestInterceptor done is 298 ms


How to use:e.g.: public class HelloInterceptor extends HttpServlet {       @EJB    private HelloBean helloBean;//.... }And: there is no XML, strange configuration, libraries, additional dependencies needed... EJB 3 interceptors will run on >10 appservers. You will find the whole executable project (tested with Netbeans 6.7 and Glassfish v3 preview) in: http://kenai.com/projects/javaee-patterns/ [project name: LeanestInterceptor].
[See also "Real World Java EE Patterns - Rethinking Best Practices", page 42]