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.
• 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.