ayodhyya.comJavaServer Pages (JSP) enable server-side HTML generation by embedding Java code within templates. While modern applications largely use client-side rendering or Thymeleaf, millions of legacy enterprise applications still rely on JSP. Understanding JSP is essential for maintaining and migrating these systems.
This tutorial covers JSP syntax, implicit objects, tag libraries, custom tags, JSTL, and best practices for separating presentation logic from business code. You will learn both classic JSP patterns and modern approaches using JSP 2.x+.
JSP Syntax and Lifecycle
JSP pages combine HTML with special tags: <%! %> for declarations, <% %> for scriptlets, <%= %> for expressions, and ${} for Expression Language (EL). The container translates JSP into a servlet class β the _jspService() method handles requests. Translation happens once, then the compiled servlet handles requests like any other servlet.
EL expressions are the preferred way to access page, request, session, and application scoped attributes. Scriptlets (<% %>) should be avoided in modern JSP β they mix Java code with markup and make pages unmaintainable. Use EL, JSTL, and custom tags instead.
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
${pageTitle}
Welcome, ${sessionScope.user.name}!
Today: ${requestScope.currentDate}
<%-- JSTL loop --%>
${order.id}
${order.total}