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Annoying Seam errors and their solutions

Published on January 19th 2010.

I started using the Java framework Seam, last year and really loved it. It combines JSF, Hibernate and Spring (to name a few) into a robust framework that's intuitive and easy to use. Like all frameworks, Seam has its little glitches...things that suddenly go wrong after deployment, or random error messages - most of which are usually down to user error. I've run into several that have really had me pulling my hair out, so I decided to compile a page devoted to solving these issues.

This guide assumes you are using Seam with jBoss Server. The operating system (unless specified) doesn't matter. I use Eclipse and several errors are specific to Eclipse, but most of them are generic, and independent of whatever tool you use to develop your Seam applications.

• javax.el.PropertyNotFoundException
• nameofyourDatasource not bound error
• Failed to connect to remote VM. Connection timed out
• [AbstractKernelController] Error installing to Start
• The prefix "a4j" for element "a4j:form" is not bound

javax.el.PropertyNotFoundException

Added on 22nd January 2010

Error

This is a Facelets error and occurs when you reference a property in your method binding that either doesn't exist, or is set to private.

Solution

Make sure you don't have any typos in your html, or your method decleration. Also, make sure your method is not set to private.

nameofyourDatasource not bound error

Added on 19th January 2010

This error message is encountered in EJB projects and will typically be displayed at the top of a very intimidating looking stack trace, similar to the following:

Error

Solution

Check your persistence.xml. This error arises because the persistence-unit does not match the jta-data-source.

You can also get this error if your jtda-data-source has the word java prefixed to it, such as <jta-data-source>java:/nameofyourDatasource</jta-data-source>.

Failed to connect to remote VM. Connection timed out

Added on 19th January 2010

This error occurs if you are using Eclipse and attempting to start jBoss from within Eclipse.

Here is the full stacktrace:

Error

Solution

This means jBoss is taking longer to start than the default time allocated to it in Eclipse's server config. To fix this, all we need to do is give jBoss more time, by increasing the timeout.

To do this, double-click on the Server tab, in Eclipse. This will bring up JBoss's configuration. You should see a Timeout section (mine is minimised, by default). If yours is minimised too, click the arrow next to it and jBoss's timeout settings will be revealed. For me, JBoss can take up to three minutes to start, so hike up the number in the Start field to something like 600. You may also want to increase the Stop time, as well, in case any issues arise while JBoss is shutting down, to prevent a nice error message from being displayed if jBoss runs out of time whilst stopping. I set mine to 40, which I find is sufficient. Now save your changes, either by hitting CTRL+S or by clicking File > Save.

Start jBoss again, and you should be error-free!

[AbstractKernelController] Error installing to Start

Added on 19th January 2010

Here is the full stacktrace - I've highlighted the meaningful parts:

Error

Solution

This error occurs when you mix your annotations - you put some annotations on the Getters and others on the field declarations. Your annotations must all be in the same place, either all on the Getters, or all on the field declarations. Not both. Ensure your annotations are on one or the other, then deploy your project. You should no longer see this error message.

The prefix "a4j" for element "a4j:form" is not bound

Added on 19th January 2010

This is a Facelets error and occurs because you are using a components without linking to its tag-library. In this example, I'm attempting to use an a4j form but I do not have xmlns:a4j="http://richfaces.org/a4j in my ui:composition.

Solution

Add the necessary tag-library to your ui:composition and all will be fine.

Note, when you use Eclipse it will underline components which are not bound, so you can easily add in their tag-libraries.