Programming Jakarta Struts, Second Edition

Exception Handling Provided by Struts

Prior to Version 1.1, the Struts framework provided very minimal exception handling for applications—it was left to you to extend the framework with your own exception-handling capabilities. This encouraged each development group to approach a solution from a different direction and made it difficult to discuss common solutions.

In Version 1.1, Struts added a small but effective exception-handling framework for your applications. The approach that the Struts designers took follows the EJB and Servlet specifications for handling security, allowing developers to use a declarative and/or a programmatic approach.

Using the AppException Class

The org.apache.struts.util.ModuleException class is included with the Struts framework. This class is a wrapper around an ActionError and extends java.lang.Exception. It provides the ability to throw exceptions in a Struts application like:

throw new ModuleException("error.password.mismatch");

where the argument to the ModuleException constructor is a resource bundle key. The framework will automatically create ActionError objects from these exceptions and store them in the appropriate scope. You can extend the ModuleException class with application-specific exceptions for your application.

One problem with using this class, however, is that it couples your application, and specifically your exception-handling code, to the Struts framework. It relies on classes that are specific to the Struts framework, which is ...