Java Server Pages

Implicit JSP Objects

When you use scripting elements in a JSP page, you always have access to a number of objects (listed in Table 6.1) that the JSP container makes available. These are called implicit objects. These objects are instances of classes defined by the servlet and JSP specifications. Appendix B, contains complete descriptions of all methods for each class, and we will cover them in more detail as we move through the book. However, I want to briefly introduce them here, as they are used in a number of examples throughout this book.

Table 6-1. Implicit JSP Objects

Variable Name	Java Type
request	javax.servlet.http.HttpServletRequest
response	javax.servlet.http.HttpServletResponse
pageContext	javax.servlet.jsp.PageContext
session	javax.servlet.http.HttpSession
application	javax.servlet.ServletContext
out	javax.servlet.jsp.JspWriter
config	javax.servlet.ServletConfig
page	java.lang.Object
exception	java.lang.Throwable

Here is some more information about each of these implicit objects:

request

The request object is an instance of the class named javax.servlet.http.HttpServletRequest. This object provides methods that let you access all the information that’s available about the current request, such as request parameters, attributes, headers, and cookies. We use the request object in a couple of examples later in this chapter.

response

The response object represents the current response message. It’s an instance of the javax.servlet.http.HttpServletResponse ...