The JSP container has a special servlet called the page compiler. All HTTP requests with URLs that match the .jsp file extension are forwarded to this page compiler by the configuration of the servlet container. The servlet container is turned into a JSP container with this page compiler. When a .jsp page is first called, the page compiler parses and compiles the .jsp page into a servlet class. The JSP servlet class is loaded into memory on the successful compilation. For the subsequent calls, the servlet class for that .jsp page is already in memory. Hence, the page compiler servlet will always compare the timestamp of the JSP servlet with the JSP page. If the .jsp page is more current, recompilation is necessary. With this process, once deployed, JSP pages only go through the time-consuming compilation process once.
