The diagram describes the framework's architecture.
In the diagram, an initial request goes to the Servlet container (such as Tomcat Jetty or Resin) which is passed through a standard filter chain. The chain includes the (optional) ActionContextCleanUp filter, which is useful when integrating technologies such as SiteMesh Plugin. Next, the required FilterDispatcher is called, which in turn consults the ActionMapper to determine if the request should invoke an action.
If the ActionMapper determines that an Action should be invoked, the FilterDispatcher delegates control to the ActionProxy. The ActionProxy consults the framework Configuration Files manager (which may read initialized from the struts.xml file). Next, the ActionProxy creates an ActionInvocation, which is responsible for the command pattern implementation. This includes invoking any Interceptors (the before method clause) in advance of invoking the Action itself.
Once the Action returns, the ActionInvocation is responsible for looking up the proper result associated with the Action result code mapped in struts.xml. The result is then executed, which often (but not always, as is the case for Action Chaining) involves a template written in JSP or FreeMarker to be rendered. While rendering, the templates can utilize use the Struts Tags provided by the framework. Some of those components will work with the ActionMapper to render proper URLs for additional requests.
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All objects in this architecture (ActionActions, Result Results, Interceptor Interceptors, and so forth) are created by an ObjectFactory. This ObjectFactory is pluggable. You We can also provide your our own ObjectFactory for any reason that requires knowing when objects in the framework are created. The default ObjectgFactory is Spring.A popular ObjectFactory implementation uses Spring as provided by the Spring Plugin. |
Finally, the Interceptors are executed again (in reverse order, calling the after method clause). Finally, the response returns through the filters configured in the web.xml. If the ActionContextCleanUp filter is present, the FilterDispatcher will not clean up the ThreadLocal ActionContext. If the ActionContextCleanUp filter is not present, the FilterDispatcher will cleanup all ThreadLocals.
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