Meeraj Kunnumpurath's Blog

Interceptors with EJB 3

I have been having a look at EJB 3.0 interceptors with Glassfish. EJB 3.0 allows you to define interceptor methods that are called around the business methods and lifecycle events on the bean instances. The interceptor methods can either be defined within the bean class or in separate interceptor classes. Interceptor definitions and binding interceptors to bean classes or specific methods within the beans can be done either using annotations or within the deployment descriptors. Here, I will try to provide a simple example of using interceptors on business methods using annotations.

Methods that intercept invocations to business methods or lifecycle events can be defined either in the bean class or in separator interceptor classes. Only one interceptor method is allowed per class. The interceptor methods should be annotated with the @AroundInvoke annotation and should have the signature, Object <methodName>(javax.ejb.InvocationContext). If the bean class has a method with the above signature and annotation, the method will be used to interpose on all the business method invocations on that bean. Additionally, you can define interceptors for all the business methods on the bean or individual business methods using the @Interceptors annotation. The value of this annotation is the list of interceptor classes. The interceptor classes are required to have a single interceptor method with the same signature and annotation as explained earlier. Interceptor classes have the same lifecycle as the associated bean instance and can have dependency injection, which will be done using the same naming context as the bean.

InvocationContext

Order of Interception

Example

Bean Class

package com.acme.ejb;

import javax.ejb.AroundInvoke;
import javax.ejb.Interceptors;
import javax.ejb.InvocationContext;
import javax.ejb.Stateless;
import javax.jws.WebMethod;
import javax.jws.WebService;

@Stateless
@WebService
@Interceptors( { Interceptor2.class })
public class HelloWorldBean {

	@Interceptors( { Interceptor1.class })
	@WebMethod
	public String sayHello() {
		return "Hello";
	}

	@WebMethod
	public String sayHi() {
		return "Hi";
	}

	@AroundInvoke
	public Object log(InvocationContext invocationContext) throws Exception {
		System.err.println(invocationContext.getMethod().getName() + " called from interceptor 3");
		return invocationContext.proceed();
	}

}

Interceptor Classes

package com.acme.ejb;

import javax.ejb.AroundInvoke;
import javax.ejb.InvocationContext;

public class Interceptor1 {

	@AroundInvoke
	public Object log(InvocationContext invocationContext) throws Exception {
		System.err.println(invocationContext.getMethod().getName() + " called from interceptor 1");
		return invocationContext.proceed();
	}

}

package com.acme.ejb;

import javax.ejb.AroundInvoke;
import javax.ejb.InvocationContext;

public class Interceptor2 {

	@AroundInvoke
	public Object log(InvocationContext invocationContext) throws Exception {
		System.err.println(invocationContext.getMethod().getName() + " called from interceptor 2");
		return invocationContext.proceed();
	}

}

Testing the Example using Glassfish

Comments

• Hi Meeraj,

  very clear article, but I have some problems implementing my own interceptors.

  I’m trying the method level interceptors. The thing is that interceptors work pretty well for methods that are the entry point of the execution flow in the class, but if those methods call other methods in the class, these calls are not intercepted.

  Is there anything that I’m missing?

  This an example of the code I’m referring to:

      @Interceptors({
  com.care.library.service.impl.interceptors.BookPreconditions.class})
      @TransactionAttribute(value=TransactionAttributeType.SUPPORTS)
      public BookOID create_instance1(ServiceContext serCtx, String pt_isbn, String pt_title, Integer pt_author) {
          Author author_pt_author = authorData.find(pt_author);
          Book book = this.create_instance2(serCtx, pt_isbn, pt_title, author_pt_author);
          return book.getOid();
      }
  
      @TransactionAttribute(value=TransactionAttributeType.REQUIRED)
      public Book create_instance2(ServiceContext serCtx, String pt_isbn, String pt_title, Author pt_author) {
          Book book = this.create_instance3(serCtx, pt_isbn, pt_title, pt_author);
          return book;
      }
  
  
      @Interceptors({
  com.care.library.service.impl.interceptors.BookPreconditions.class})
      public Book create_instance3(ServiceContext serCtx, String pt_isbn, String pt_title, Author pt_author) {
          Book book = bookData.create(pt_isbn, pt_title, pt_author);
          return book;
      }
  

  And the interceptor

  public class BookPreconditions {
      /* logging service */
      private static final Logger LOGGER = Logger.getLogger(BookPreconditions.class.getName());
  
      @AroundInvoke
      public Object preconditionInterceptor(InvocationContext ctx) throws Exception
      {
          LOGGER.info("Preconditions Check...[" + ctx.getMethod().getName() + "]");
          if (ctx.getMethod().getName().equals("create_instance3")) {
              create_instance(ctx);
          }
          return ctx.proceed();
      }
  

  The method create_instance1 is being intercepted while the method create_instance3 is not. Why?

  ..:: Carlos ::..

  Posted by: cgarcia on May 08, 2006 at 10:26 AM

• Excellent tutorial, Meeraj. Do you have any references or pointers to other resources on Interceptors?

  Posted by: rudradixit on April 20, 2007 at 07:20 AM

• I dont know if its possible but I'm trying to use EJB3 logging interceptor to work on non-EJB classes like struts actions and DAOs. Is it possible?

  Posted by: sim4life on July 05, 2007 at 12:56 AM

• Hi, I even have similar problem. Meeraj, can you please comment on the above issue ? Many Thanks, Praveen

  Posted by: praveen_dvk on March 27, 2008 at 04:41 PM

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