Struts%20Interview%20Questions%20and%20Answers

Question: Multiple Sub-applications

Answer: One of the shortcomings in Struts 1.0 is manageability of the configuration file (commonly known as struts-config.xml) when the development of the application involves a sizable team. This problem arises because a Struts-based application must run under one controller servlet, the ActionServlet, and the ActionServlet can use only one struts-config.xml. It is not an issue when the project is relatively small and the team consists of a couple of developers; however, when the project size becomes significant and the project involves a large number of developers, maintaining all the mapping information in a single file becomes increasingly problematic.
Struts 1.1 solves this problem nicely by introducing multiple sub-applications. In Struts 1.1, each sub-application has its own struts-config.xml file. A large Struts-based application can thus be easily partitioned into largely independent modules, i.e. sub-applications, and each sub-team can maintain their struts-config.xml independently.
The sub-application scheme is a natural extension of the servlet context mapping scheme of the URI paths used by servlet containers. According to the Servlet standard, when the servlet container receives a request with a URL, the servlet container will try to match the prefix of the URI path to a deployed web-application in the container. What Struts 1.1 does is it maps the second prefix of the path to a sub-application. In effect, this prefix mapping scheme creates another level of namespace for each sub-application. For example, for the URI,
http://some-host.com/myApp/module2/editSubscription.do
/myApp is the context path for a web-application called "myApp" and /module2 is the sub-app prefix for a Struts sub-application called "module2".