JSP (Java Server Pages)
Dynamic web pages with embedded Java code
📄 What is JSP?
JSP (Java Server Pages) is a technology for creating dynamic web pages by embedding Java code directly into HTML. It simplifies web development by separating presentation from business logic.
<%-- Simple JSP Example --%>
<%@ page language="java" contentType="text/html; charset=UTF-8" %>
<html>
<head>
<title>Hello JSP</title>
</head>
<body>
<h1>Welcome to JSP!</h1>
<p>Current time: <%= new java.util.Date() %></p>
<p>Random number: <%= Math.random() * 100 %></p>
</body>
</html>
Output (in browser):
Welcome to JSP!
Current time: Thu Jan 18 14:30:25 PST 2024
Random number: 73.42
Key JSP Concepts
Directives
Page configuration and imports
<%@ page import="java.util.*" %>
<%@ include file="header.jsp" %>Scriptlets
Embedded Java code blocks
<%
String name = "World";
out.println("Hello " + name);
%>Expressions
Output Java expressions directly
<%= userName %>
<%= 2 + 3 %>Actions
JSP standard action tags
<jsp:include page="menu.jsp" />
<jsp:forward page="login.jsp" />🔹 JSP Syntax Elements
Different ways to embed Java code in JSP pages:
<%-- JSP Comment (not sent to client) --%>
<!-- HTML Comment (sent to client) -->
<%-- Page Directive --%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
import="java.util.*, java.text.*" %>
<html>
<head>
<title>JSP Syntax Demo</title>
</head>
<body>
<h2>JSP Syntax Elements</h2>
<%-- Declaration: Define variables and methods --%>
<%!
private int counter = 0;
private String formatDate(Date date) {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
return sdf.format(date);
}
%>
<%-- Scriptlet: Java code block --%>
<%
counter++;
String userName = request.getParameter("name");
if (userName == null) {
userName = "Guest";
}
Date currentDate = new Date();
%>
<%-- Expression: Output values --%>
<p>Welcome, <%= userName %>!</p>
<p>Page visits: <%= counter %></p>
<p>Current time: <%= formatDate(currentDate) %></p>
<%-- Conditional logic --%>
<% if (counter > 5) { %>
<p style="color: red;">High traffic detected!</p>
<% } else { %>
<p style="color: green;">Normal traffic</p>
<% } %>
</body>
</html>🔹 JSP Implicit Objects
Built-in objects available in JSP pages:
<%@ page language="java" contentType="text/html; charset=UTF-8" %>
<html>
<body>
<h2>JSP Implicit Objects Demo</h2>
<%-- request object --%>
<p>Request Method: <%= request.getMethod() %></p>
<p>Request URI: <%= request.getRequestURI() %></p>
<p>Client IP: <%= request.getRemoteAddr() %></p>
<%-- response object --%>
<% response.setHeader("Custom-Header", "JSP-Demo"); %>
<%-- session object --%>
<%
Integer visitCount = (Integer) session.getAttribute("visits");
if (visitCount == null) {
visitCount = 1;
} else {
visitCount++;
}
session.setAttribute("visits", visitCount);
%>
<p>Session ID: <%= session.getId() %></p>
<p>Visit Count: <%= visitCount %></p>
<%-- application object --%>
<p>Server Info: <%= application.getServerInfo() %></p>
<p>Context Path: <%= application.getContextPath() %></p>
<%-- out object --%>
<%
out.println("<p>This is printed using out object</p>");
out.flush();
%>
<%-- config object --%>
<p>Servlet Name: <%= config.getServletName() %></p>
<%-- pageContext object --%>
<% pageContext.setAttribute("message", "Hello from pageContext!"); %>
<p>Page Message: <%= pageContext.getAttribute("message") %></p>
</body>
</html>🔹 JSP Standard Actions
Built-in action tags for common operations:
<%-- Include another JSP page --%>
<jsp:include page="header.jsp" />
<%-- Forward to another page --%>
<% if (user == null) { %>
<jsp:forward page="login.jsp" />
<% } %>
<%-- Use JavaBean --%>
<jsp:useBean id="user" class="com.example.User" scope="session" />
<jsp:setProperty name="user" property="name" value="John Doe" />
<jsp:getProperty name="user" property="name" />
<%-- Include with parameters --%>
<jsp:include page="menu.jsp">
<jsp:param name="activeTab" value="home" />
</jsp:include>
<%-- Plugin for applets (rarely used now) --%>
<jsp:plugin type="applet" code="MyApplet.class"
width="300" height="200">
<jsp:fallback>
<p>Your browser doesn't support applets.</p>
</jsp:fallback>
</jsp:plugin>🔹 Form Processing with JSP
Handling HTML forms in JSP pages:
🔸 Form Page (form.jsp)
<%@ page language="java" contentType="text/html; charset=UTF-8" %>
<html>
<head>
<title>User Registration</title>
<style>
.form-group { margin: 10px 0; }
input[type="text"], input[type="email"], select {
width: 200px; padding: 5px;
}
</style>
</head>
<body>
<h2>User Registration Form</h2>
<form action="process.jsp" method="post">
<div class="form-group">
<label>Name: </label>
<input type="text" name="name" required>
</div>
<div class="form-group">
<label>Email: </label>
<input type="email" name="email" required>
</div>
<div class="form-group">
<label>Age: </label>
<input type="number" name="age" min="1" max="120">
</div>
<div class="form-group">
<label>Country: </label>
<select name="country">
<option value="USA">United States</option>
<option value="UK">United Kingdom</option>
<option value="CA">Canada</option>
<option value="AU">Australia</option>
</select>
</div>
<div class="form-group">
<input type="submit" value="Register">
<input type="reset" value="Clear">
</div>
</form>
</body>
</html>🔸 Processing Page (process.jsp)
<%@ page language="java" contentType="text/html; charset=UTF-8" %>
<html>
<head>
<title>Registration Result</title>
</head>
<body>
<h2>Registration Successful!</h2>
<%
// Get form parameters
String name = request.getParameter("name");
String email = request.getParameter("email");
String ageStr = request.getParameter("age");
String country = request.getParameter("country");
// Validate and process data
if (name != null && !name.trim().isEmpty()) {
%>
<div style="border: 1px solid #ccc; padding: 15px; margin: 10px 0;">
<h3>User Information:</h3>
<p><strong>Name:</strong> <%= name %></p>
<p><strong>Email:</strong> <%= email %></p>
<% if (ageStr != null && !ageStr.isEmpty()) { %>
<p><strong>Age:</strong> <%= ageStr %> years old</p>
<% } %>
<p><strong>Country:</strong> <%= country %></p>
<p style="color: green;">
<strong>Registration completed at:</strong>
<%= new java.util.Date() %>
</p>
</div>
<%
// Here you would typically save to database
// Database.saveUser(name, email, age, country);
%>
<% } else { %>
<p style="color: red;">Error: Name is required!</p>
<% } %>
<p><a href="form.jsp">Register Another User</a></p>
</body>
</html>🔹 JSP vs Servlets
Understanding when to use JSP vs Servlets:
JSP Advantages:
- Easy HTML integration: Mix HTML and Java seamlessly
- Rapid development: Faster for presentation layer
- Automatic compilation: No manual servlet compilation
- Designer-friendly: Web designers can work with HTML parts
When to use JSP:
- Presentation layer with dynamic content
- Reports and data display pages
- Form-based applications
- Content management systems
When to use Servlets:
- Business logic and data processing
- API endpoints and web services
- Complex request handling
- File uploads and downloads