Chapter 5. Retrieving Information

Topics in this Chapter:

• The Request

• Receiving parameter information

• Receiving header information

• Receiving attribute information

• Getting information about the server

JSP pages, like most Web application platforms, use HTTP as a transport protocol. To understand how a JSP program changes for different requests, one must understand the Web transaction model, which is built on HTTP. The model itself is very simple, and it applies to many different Web-programming technologies. A good analogy for the Web transaction model is a math function box. Math function boxes are a tool to explain how mathematical functions work. The important thing to understand is that the function box itself never changes. The only reason an output changes is if input changes. It is exactly the same with JSP pages. The JSP page itself does not change, but it generates different output based on different input. (see Figure 5-1).