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Welcome to the Struts 2 (S2) CRUD Example. This example was created to be as simple as possible and as such, it does not use all of the advanced (integration) features such as Spring IoC, Hibernate Open-session-in-view, OS Sitemesh, annotations, etc .. For these and other examples, please refer to the Struts 2 Guides.

Struts 2

Struts 2 is a traditional MVC2 action-based framework (such as Struts 1, Stripes, Simple, ..) as opposed to the newer event-based frameworks (such as JSF, Wicket, Rife, ..). Struts 2 uses XWork under the hood, a command-pattern based framework that handles conversion, validation, interception, and a lot more. Struts 2 is based on WebWork, which was originally started as an effort to overcome some problems with Apache Struts 1.

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struts.xml contains the configuration for XWork: actions, validation, interceptors and results are defined in there.
To understand these terms, we'll need to take a look at Struts 2's (and XWork's) architecture. A basic request goes a bit like this:
A request is submitted, and our ActionMapper will try to determine the correct Action to execute. To find it, it will look up the registered names in your struts.xml. If one is found, before executing the Action, it will loop through a defined stack of interceptors.

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    [Learn More About Interceptors|Interceptors]
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Interceptors are a very important part of S2 - they will be invoked before and after your action is executed and the view is rendered, and as such, they are perfect for validation, authentication, open-session-in-view patterns, catching exceptions, setting or altering parameters, hiding complex operations, and more. S2 provides a number of prebuilt stacks with a ranging number of features, but nothing keeps you from defining your own interceptor stack with custom interceptors.

One of the most practical interceptors is the 'params' interceptor. It will translate your request parameters to set them on your action. Thus, if your action had a setName(String), and one of your request parameters is called 'name', then WW will set the name for you. Not so special, you say ? Ok, how about setId(Long id) ? This will work just fine as long as your id parameter value can be converted to a Long. Still not special enough ? How about submitting a parameter named empolyee.id ? As you might have guessed, this will invoke a getEmployee().setId(Long id). S2 handles all common objects (Integer, String, Date, .. and Arrays, Lists, Maps, ..) And for those who just can't get enough, you can always add your own convertors for those (or your own) very complex objects (think social security number).

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