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Exceptions are a fact of life. As developers, we need to be prepared to deal with them in the most graceful manner possible. Seam Catch provides a simple, yet robust foundation for modules and/or applications to establish a customized exception handling process. By employing a delegation model, Catch allows exceptions to be addressed in a centralized, extensible and uniform manner.
In this guide, we'll explore the various options you have for handling exceptions using Catch, as well as how framework authors can offer Catch integration.
Seam Catch is based around the CDI eventing model. While the implementation of exception handlers may not be the same as a CDI event, and the programming model is not exactly the same as specifying a CDI event / observer, the concepts are very similar. Seam Catch makes use of events for many of it's features. Eventing in is actually the only way to start using Catch.
This event is fired either by the application or a Catch integration. Catch then hands the exception off to a chain of registered handlers, which deal with the exception appropriately. The use of CDI events to connect exceptions to handlers makes this strategy of exception handling non-invasive and minimally coupled to Catch's infrastructure.
The exception handling process remains mostly transparent to the developer. In most cases, you register an exception handler simply by annotating a handler method. Alternatively, you can handle an exception programmatically, just as you would observe an event in CDI.
There are other events that are fired during the exception handling process that will allow great customization of the exception, stack trace, and status. This allows the application developer to have the most control possible while still following a defined workflow. These events and other advanced usages will be covered in the next chapter.