A Brief Overview of Java Server Page (JSP) programming
JSP has four predefined variables:
- request
- the HttpServletRequest object
- response
- the HttpServletResponse object
- out
- PrintWriter object used to send output to client
- session
- HttpSession object associated with request
JSP includes four scripting elements:
- JSP page directive
<%@ page import="java.util.*" %>
- The main use of a JSP page directive is to include imports for the compiler.
- JSP declaration
<%! private int accessCount=0; %>
- A JSP declaration is used to define, and possibly initialize, a variable. The declaration is executed only the first time the .jsp page is executed (after translation).
- JSP expression
<%= new Date() %>
- A JSP "expression" is used to insert a value directly into the output. The expression
is evaluated, converted to a String, and inserted into the page.
- A JSP "expression" is used to insert a value directly into the output. The expression
- JSP scriptlet
<%
String wordList=(String) session.getAttribute("wordList");
if(wordList==null)
{
out.println("wordList is empty");
}
else
{
out.println(wordList);
}
%>
- A JSP "scriptlet" is a block of Java code that will be executed.