WebWork Lifecycle
The architecture of WebWork is based on the MVC, Command, and Dispatcher patterns and the principle of Inversion of Control. The life cycle of a WebWork request begins when the servlet container receives a new request. The new request is passed through a set of filters called the filter chain and sent to the FilterDispatcher. The FilterDispatcher forwards the request to the ActionMapper to determine what needs to be done with the request. If the request requires an action, it sends an ActionMapping object back to the FilterDispatcher. If not, ActionMapper returns a null object, indicating that no action needs to be taken. The FilterDispatcher forwards the request and the ActionMapper object to the ActionProxy for further action. The ActionProxy invokes the Configuration File manager to get the attributes of the action, which is stored in the xwork.xml file and creates an ActionInvocation object. The ActionInvocation object contains attributes like the action, invocation context, result, result code, etc. The configuration file manager has access to these configuration files and is used by the ActionProxy as a gateway to the configuration files. The ActionInvocation object also has information about Interceptors that need to be invoked after or before an action is executed.
ActionInvocation invokes all the interceptors listed in the ActionInvocation object and then invokes the actual action. When the action is completed, ActionInvocation gets the action result code from the execution. It uses the action result code to look up the appropriate result, which is usually a JSP page, a velocity template or a freemarker template associated with the result code. ActionInvocation also executes the interceptors again in the reverse order and returns the response as a HttpServletResponse.
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