JavaServer Pages, 3rd Edition

Servlet Contexts and Web Applications

A Java web application is typically made up by a combination of several different types of resources: JSP pages, servlets, applets, static HTML pages, custom tag libraries and other Java class files. Containers compliant with the Servlet 2.2 specification (or later), support a standard, portable way to package all these resources, along with a web application deployment descriptor containing information about how all the resources fit together. The deployment descriptor and all the other web application files are arranged in a well-defined hierarchy within an archive file, called a web application archive (WAR). All compliant containers provide tools for installing a WAR file or a special directory where a WAR file is automatically picked up (such as the webapps directory in Tomcat). Most containers also support web applications deployed directly in a filesystem using the same file structure as is defined for the WAR file, which can be convenient during development.

Within the container, each web application is represented by a servlet context. The servlet context is associated with a unique URI path prefix called the context path, as shown in Figure 2-4. For instance, your human resources application can be associated with the context path /hr and your sales tracking system with the context path /sales. This allows one servlet container to distinguish between the different applications it serves and dispatch requests like /sales/report?month=Jan ...