WebSphere Application Server - IBM Redbooks

In fact, in WebSphere’s JSP implementation, the foo.jsp file is translated into two
files: A .java file containing the Java code for the servlet, and a .dat file containing
the static elements of the JSP. The .dat file actually contains a serialized array of
byte arrays, with each byte array containing the static page elements before the
next JSP tag. The .java file is then compiled to create a .class file, which
represents the compiled servlet.
The .class and .dat files are stored on the file system. The .java file may or may
not be retained after the translation stage. This translation phase is performed
once per JSP. If a compiled class file already exists on the file system, then the
request for the JSP proceeds directly to phase 2.
Phase 2: Request processing
Phase 2 represents the actual invocation of the compiled servlet—the JSP page
implementation class—to provide a response to the initial request.
For Request 1, this phase is entered immediately after phase 1. If the servlet is
not already loaded, it is brought into memory and the request serviced.
For Request 2, the Web container knows of the existence of an already compiled
servlet class loaded in memory, and directly services the request.
By default, the JSP implementation in WebSphere also checks the source .jsp
file for changes. If it has been modified it will enter the translation phase. Each
subsequent request is handled by the servlet until the servlet is unloaded from
memory, for instance, when the application server is stopped. This load/service
request/unload life cycle is exactly the same as for servlets.
8.1.2 Syntax for coding JavaServer Pages
JavaServer Pages can be coded using two alternative methods: JSP syntax or
XML syntax. The two cannot be mixed within a page. Beginning with JSP 1.2,
JSP pages written in XML (referred to as JSP documents) can be delivered to the
Web container for processing.
The traditional JSP syntax looks like that shown in Example 8-1.
Example 8-1 JSP syntax