Request Processing in ATG

In every web application request plays a very important role.User(browser) need to send request to server to access any web resource.

ATG performs below steps to process requests it receives.

1. When a user requests a page(send request to server).Web server parses the request and holds in an HTTPServletRequest object.
2. The Web server passes the HTTPServletRequest to the application server.It wraps the request in its own flavor of request around the generic one before passing it to the Web application.
3. If you defined custom filters and the request is for a JHTML page, the filters execute in the order you specified.
4. Any custom J2EE servlets are processed.
5. The Web application calls one of the following resources.

•  DynamoProxyServlet( DAS servlet pipeline for JHTML requests).
•  PageFilter (DAF servlet pipeline for JSP requests).

     6. The request is passed on to a pipeline of servlets.
     7. If you created custom filters and a JSP is being requested, they execute after the last pipeline servlet, but before the request returns to the application server.
     8. After the servlet pipeline reaches the end, it returns the request to the application server for final processing. 

Below diagram illustrates ATG request processing.
 

Note : DAS pipeline is invoked in the case of JHTML.Because JHTML is a proprietary language, it relies on the page compiler provided in the DAS servlet pipeline to generate JHTML into a servlet that is rendered as HTML by the application server.