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The Control Servlet is at the heart of all request processing. Valid requests which pass through the Context Security Filter begin processing here. When a request is received, the Control Servlet first sets up an environment for the helper classes. This environment includes (but is not limited to) setting up an initial session object and storing useful information about the initial request and setting a reference to the Entity Delegator, Service Dispatcher, and Security Handler for use by the helper classes. The request is then passed to the Request Handler for processing. The Request Handler processes the request and  returns to the ControlServlet when finished.

When the Control Servlet is first loaded it will create objects used by the web application and store them in the application context (ServletContext). These objects can be found by accessing the property in the context or via a JSP <useBean> tag. These objects include: Entity Delegator, Security object, Service Dispatcher, and the Request Handler.

Request Handler

The Request Handler makes use of a RequestManager helper class to gather a list of request mappings defined in an XML configuration file. The configuration file lives in /WEB-INF/controller.xml for the appropriate context. The mapping consists of a request URI and an optional VIEW name. View names are mapped to in the configuration file as well. A request URI can also be associated with an Event. Events are used to process web related logic by either working directly with the Entity Engine through the Entity Delegator or invoking service(s) to handle the logic through the Service Dispatcher.

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Java events are processed by locating the path of the event (package and classname); then, by using the Reflection API, the Event Handler invokes the method defined. A String object is returned to the Request Handler which is mapped to the response element of the request definition.

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