JavaServer Pages (JSP) is a server-side technology used for creating dynamic web pages in Java-based web applications. It allows developers to embed Java code into HTML and generate dynamic content at runtime. JSP is part of Java EE (Jakarta EE) and is built on top of Servlets, making it an extension of the Java Servlet technology.
Key Features
- Dynamic HTML content generation using Java code.
- Separation of presentation & logic with JavaBeans and MVC pattern.
- Reusable components using JSP tags and JavaBeans.
- Integration with Servlets for advanced web applications.
- Session management, form handling, and database connectivity.
Example Syntax:
<%@ page language="java" contentType="text/html" %>
<html>
<body>
<h1>Welcome to JSP!</h1>
<p>The current time is: <%= new java.util.Date() %></p>
</body>
</html>
<%= expression %>inserts dynamic content into HTML.
Elements & Syntax
| JSP Element | Description | Example |
|---|---|---|
| Directives | Provide instructions to the JSP engine. | <%@ page language="java" contentType="text/html" %> |
| Declarations | Declare variables & methods in Java. | <%! int count = 0; %> |
| Scriptlets | Java code inside JSP. | <% out.println("Hello, JSP!"); %> |
| Expressions | Insert dynamic values. | <%= new java.util.Date() %> |
| Comments | Add server-side comments. | <%-- This is a JSP comment --%> |
| Implicit Objects | Predefined objects like request, response, session, etc. | <%= request.getParameter("name") %> |
JSP Implicit Objects
JSP provides built-in objects for handling requests, responses, and session management.
| Object | Description |
|---|---|
request | Holds HTTP request data (parameters, headers). |
response | Sends response data to the client. |
session | Stores user session data. |
application | Stores application-wide data. |
out | Writes content to the response. |
config | Retrieves JSP configuration settings. |
pageContext | Provides information about the page execution. |
exception | Captures exceptions (used in error pages). |
JSP with JavaBeans Example
JavaBean Class (User.java)
package com.example;
public class User {
private String name;
public String getName() { return name; }
public void setName(String name) { this.name = name; }
}JSP Page (user.jsp)
<jsp:useBean id="user" class="com.example.User" />
<jsp:setProperty name="user" property="name" value="Alice"/>
<p>Welcome, <jsp:getProperty name="user" property="name"/>!</p>Uses JavaBean to separate business logic from JSP presentation.
JSP in MVC Architecture
JSP is often used in Model-View-Controller (MVC) pattern:
- Model (M): JavaBeans, Database logic.
- View (V): JSP pages (UI).
- Controller (C): Servlets handling requests.