Does Tomcat 5.5 support EJB 2.0 and Message Driven Beans?

Tomcat is servlet container only - no EJB's at all.

JBoss comes with Tomcat and have full EJB support (and the price is the same).

Tomcat does not have builtin JMS support, but you can embed a message queue
system in Tomcat yourself.

Thanks for your answer!

Perhaps I could ask you what you think of this.

A customer just have Licencse for WebLogic 8.1 that supports EJB 1.0

The customer needs a asynchrone integration between WebLogic and WebSphere our suggested solution is JMS and use of MDB:s. But as, I guess told me, MDB:s is only available in EJB 2.0 we got a problem.

The upgrade for a WebLogic license for this customer to be able to use EJB 2.0 is a big investment.

So now we are looking for either other cheaper applicationservers that supports EJB 2.0 or some other solution then MDB:s.

Perhaps JBoss with Tomcat will be the only solution or is there some alternative to a own MDB-implemtation that just need EJB 1.0?

It may sound like this is a stupid idea to try to implement a own solution of MDB.

What do you think?

Best regards

Fredrik

According to http://e-docs.bea.com/wls/docs81/compatibility/compatibility.html
WebLogic 8.1 i J2EE 1.3 compatible which implies EJB 2.0 support.

But I assume you mean 6.1 or 7.0 or some other old versions that only support EJB 1.x.

JBoss (with Tomcat) sounds as an excellent solution.

Hello!

Thanks for your answer. According to the link in your reply I must say that it seems very strange that our customer says that they do not have a WebLogic Licens of 8.1 that do not support EJB 2.0 and MDB:s. I need to verify this. If thay have license for a WebLogic 8.1 like your link refers to then the problem is solved, right?

How ever I have heard that thay have some cheap licens for WebLogic 8.1 that just supports EJB 1.0. Thats way we got this problem. Unfortunately our projectmanager just accepted to implement an integration based on JMS.

The solution now is looking:
weblogic got 2 server instances
Server a got a webapp.
Server b got a ejbapp with MDB:s

When sometihing happens (a specific database update) on a, b gets notfied via JMS and MDB:s and take care of the task for a.

Assume that the customer just have EJB 1.0 and do not want to invest anything more in licenses, during the night I thought of this solution then without MDB:

weblogic got 2 server instances
Server a got a webapp.
Server b got a threaded app that every minute checks a queue for new JMS-messages from a. If there is any messages b consumes the messages and performs the tasks for a.

Do you see anything bad with this solution? Using a thread to schedule a task perhaps is bad. Perhaps there is anything built in in appserevers that we could use instaead?

Any comments is appreciated?

Best regards
Fredrik

Hello!

We just did a very quick test for a own home-made solution for MDB:s.

In the JMS-api there is a method "setMessageListener" in the TopicSubscriber interface. We created a Servlet that in the init method does something like this:

properties = new java.util.Properties();
properties.load(new FileInputStream(fileName));
properties.setProperty("java.naming.provider.url", properties.getProperty("protocol")+properties.getProperty("url")+properties.getProperty("port") );
jndiContext = new InitialContext(properties);

topicConnectionFactory = (TopicConnectionFactory)jndiContext.lookup( properties.getProperty("connectionfactory") ); 
topicConnection = topicConnectionFactory.createTopicConnection();
topicConnection.start();

topicSession =  topicConnection.createTopicSession(false, Session.AUTO_ACKNOWLEDGE);       
topic = (javax.jms.Topic) jndiContext.lookup(topicName);
TopicSubscriber topicSubscriber = topicSession.createSubscriber(topic);

topicSubscriber.setMessageListener(new OrderManager());

The Servlet creates a TopicSubscriber that has a MessageListener in form of a class called OrderManager. The servlet is loaded at start up like:

  <servlet>
    <servlet-name>BeanInitServlet</servlet-name>
    <servlet-class>BeanInitServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>


The Ordermanager Looks like:


import java.util.*;
import javax.naming.NamingException;
import javax.jms.*:
import java.io.*;

import javax.jms.ObjectMessage;

public class OrderManager implements MessageListener
{

    public void onMessage(Message message)
    {
        try
        {
            TextMessage textMessage = (TextMessage)message;

            System.out.println(textMessage.getText());

        }
        catch(Exception e)
        {
        }
    }
}

This acctually works fine!

Could it be like this the MDB-framework is implemented i a applicationserver?

Do you see anything crazy or that it may result in bad performance with this solution in comparation to a real MDB-solution?

Best regards
Fredrik

The listener is many times better than a polling thread.

Functional your code appears to be doing what a MDB are doing.

But there are differences.

The biggest is probably that a MDB participate in EJB transactions !

Hello!

Thank you for your very interesting comment. I guess what you say means that my code my be very risky then.

I have to admit that I do not know what or when to use EJB-transactions. Could I ask you to "describe" a very small scenario about it. I just know about JDBC-transactions. Suppose that we should do 2 updates for each received JMS-message. If the second fails we should rollback the first one. Does the EJB-transactions fit in this simple scenario or is it on a higher level thats probaply is new to me?

Best regards
Fredrik

Not necesarrily risky. It depends entirely on whether your code
is depending on EJB transaction support or not. But it is a service
that your alternative code does not provide.

The important thing is that if you have a transaction then a rollback will
rollback all database changes and the message will be redelivered.

Hello!

Thanks agian for your very interesting comments.

I have been looking at Geronimo from apache. Perhaps this is a solution for us.

I guess it is a freeware/opensource if I'm right and it looks like it uses OpenEJB that might support EJB 2.0 => MDB-support.

I tried just to set up a OpenEJB server but I did not got it to work.

Best regards
Fredrik

BTW give a svar so I can reward you.
Fredrik

I am sure that Geronomi supports EJB 2.0 probably also 2.1

personally I like JBoss

svar