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Archive for the ‘GWT’ Category

Tomcat 6+: Infamous “SEVERE: Error listenerStart” message – How-To debug this error?

Posted by Venkatt Guhesan on July 1, 2011

I’m sure if you have been developing with Java and Tomcat for sometime, you are likely to run into the infamous debug error.

SEVERE: Error listenerStart

You will most likely start Googling it trying to find out what the heck is going on. And in trying to see the extended logging on what that “listenerStart” error means. After some lucky searches, you will see links asking you to drop a “” file under ‘/WEB-INF/classes’ directory inside your WAR to help debug which one of the listeners is throwing this crazy error.

Well, this advise will most likely work for you if you are developing under an earlier version of Tomcat. If you are using versions 6.0 or above then continue to read on…

In Tomcat 6 or above, the default logger is the”java.util.logging” logger and not Log4J. So if you are trying to add a “” file – this will NOT work. The Java utils logger looks for a file called “” as stated here:

So to get to the debugging details create a “” file under your”/WEB-INF/classes” folder of your WAR and you’re all set.

And now when you restart your Tomcat, you will see all of your debugging in it’s full glory!!!

Sample file:

org.apache.catalina.core.ContainerBase.[Catalina].level = INFO
org.apache.catalina.core.ContainerBase.[Catalina].handlers = java.util.logging.ConsoleHandler

and you will most likely see a “class-not-found” exception. 😉

Look at the bright side, you’re now one step closer to the solution.

Happy coding!

Posted in Grails, Groovy, GWT, Java, Spring, Spring Framework, Tomcat, web development | Tagged: , , , , , | 25 Comments »

Maven – GWT – Vaadin – including additional custom jars in a maven project under “\web-inf\lib”

Posted by Venkatt Guhesan on September 15, 2010

With a lot of folks trying Google Web Toolkit (GWT) and\or Vaadin (combined with Maven), one of the problems that they might encounter is this:

How do I get my custom Vaadin themes or GWT jar files included under my “\web-inf\lib” folder inside the war

Here’s a link to the such a question in detail.

The answer is a lot simpler than you think. But before we explore the answer, I should warn you that this approach is going away from what Maven would like you to do. In Maven, you can take each of your jars\libraries and add them to your local repository and then include them as needed in your projects. If you want to go the proper route here’s how you do it. This keeps a consistent version in all your projects and can allow you to gracefully update the library as new versions become available.

But if you still want to go ahead and add these custom jars in your project then follow these steps:

  1. Create a “lib” folder under your project like this: “\src\main\webapp\WEB-INF\lib”
  2. Copy needed “jars” etc that you want included inside your WAR bundle folder.
  3. Invoke your maven build as you normally do. I use “mvn install”, which creates builds the war file.

If you examine the WAR file, your jars that you included in step-1 and step-2 will be there.

By the way, have you tried Vaadin lately? To summarize my experience with Vaddin… “It’s a breath of fresh air. Simple. Elegant. Concise.”


Posted in GWT, Java, Maven, Vaadin | Tagged: , , , | Leave a Comment »

GWT and Spring Integration – is a restricted class

Posted by Venkatt Guhesan on September 12, 2010

When trying to integrate both Spring and GWT, one might encounter the following error in the Spring Eclipse IDE:

“ is a restricted class”. The problem happens when you try to use Spring configuration for your database. In my case, I was using Spring to update data back to a H2 database.

Well, here’s one way to deal with this issue. Disable the “Google App Engine”. Yes, based on my research, if you’re using  GWT, you can disable Google App Engine and still continue your development with GWT.

You can right click on your project and go into properties. Under [Google] -> [App Engine], you can “uncheck” – use Google App Engine. And rebuild the application and resume your debugging.

This allows you to use Spring beans to persist your data in a database.


Posted in GWT, Java | Tagged: , , | 1 Comment »