Servlets
Servlets are Java programs that use the Java Servlet Application Programming Interface (API). You must package servlets in a Web archive (WAR) file or Web module for deployment to the appserver. Servlets run on a Java-enabled Web server and extend the capabilities of a Web server, similar to the way applets run on a browser and extend the capabilities of a browser.
Servlets can support dynamic Web page content, provide database access, serve multiple clients at one time, and filter data.
For the purposes of WAS, discussions of servlets focus on Hyper Text Transfer Protocol (HTTP) servlets, which serve Web-based clients.
With the introduction of Java Servlet 2.4 specification, you can define servlets as welcome files. Non-servlet resources are served only when the FileServingEnabled attribute is set to true. Serving welcome files is connected to serving static content, therefore fileServing enabled is set in the Web module.
Context parameters
A servlet context defines a server's view of the Web application within which the servlet is running. The context also allows a servlet to access resources available to it. Using the context, a servlet can log events, obtain URL references to resources, and set and store attributes that other servlets in the context can use. These properties declare a Web application's parameters for its context. They convey setup information, such as a webmaster's e-mail address or the name of a system that holds critical data.
Servlet mappings
A servlet mapping is a correspondence between a client request and a servlet. Web containers use URL paths to map client requests to servlets, and follow the URL path-mapping rules as specified in the Java Servlet specification. The container uses the URI from the request, minus the context path, as the path to map to a servlet. The container chooses the longest matching available context path from the list of Web applications that it hosts.
Related tasks
Developing servlets with WAS extensions
Related Reference
Web applications: Resources for learning