Understanding JSP

Understanding JSP (JavaServer Pages)

Understanding JSP


JavaServer Pages (JSP) is a core technology in Java-based web development that allows developers to create dynamic web pages using HTML combined with Java code. 

JSP was introduced to simplify the development of web user interfaces and to improve the separation between business logic and presentation logic.

Although modern frameworks such as Spring MVC and Spring Boot are widely used today, JSP remains an important technology to understand. 

Many existing enterprise systems still rely on JSP, and modern frameworks internally build on concepts originally introduced by JSP and servlets.


1. What Is JSP? (Overview)

JSP (JavaServer Pages) is a server-side technology used to generate dynamic web content. 

A JSP file typically contains:

  • HTML for layout

  • JSP tags and expressions for dynamic data

  • Optional Java code (scriptlets)

When a client requests a JSP page, the server converts the JSP into a Servlet, compiles it, and executes it. 

The output is then sent to the browser as standard HTML.

In simple terms:

  • JSP focuses on presentation

  • Servlets focus on request handling and business logic




2. Why Use JSP?

JSP was designed to solve problems that arose when developers tried to generate HTML directly inside servlets.

Main Goals of JSP

  • Improve code readability

  • Separate UI from business logic

  • Make web development easier and faster

  • Allow designers and developers to collaborate efficiently




3. JSP Processing Lifecycle

The lifecycle of a JSP page includes the following steps:

  1. Translation – JSP is translated into a servlet

  2. Compilation – The servlet is compiled into bytecode

  3. Initialization – The servlet is initialized

  4. Request Processing – The _jspService() method handles requests

  5. Destruction – The servlet is destroyed when the application stops

Because JSP is compiled into a servlet, its runtime performance is comparable to servlets.



4. JSP Directives

JSP directives provide instructions to the JSP container on how to process a page.

4.1 Page Directive

Defines page-level settings such as content type and imports.

<%@ page language="java" contentType="text/html; charset=UTF-8" %>

Common attributes:

  • language

  • contentType

  • import

  • session


4.2 Include Directive

Includes the content of another file at translation time.

<%@ include file="header.jsp" %>

Used for reusable components such as headers and footers.


4.3 Taglib Directive

Declares a tag library such as JSTL.

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>



5. Template Data and Script Elements

5.1 Template Data

Template data refers to static HTML or text in a JSP page.

<h1>Welcome to JSP Tutorial</h1>

This content is sent directly to the client without modification.


5.2 JSP Script Elements

5.2.1 Scriptlets

Used to embed Java code.

<%
    int count = 10;
%>

Scriptlets are discouraged in modern JSP development.


5.2.2 Expressions

Outputs the result of a Java expression.

<p>Count: <%= count %></p>


5.2.3 Declarations

Used to declare variables and methods.

<%! 
    int totalUsers = 100; 
%>



6. JSP Implicit Objects

JSP provides built-in objects automatically available in JSP pages:

  • request

  • response

  • session

  • application

  • out

  • config

  • pageContext

Example:

<p>Client IP: <%= request.getRemoteAddr() %></p>



7. JSP Practical Programming Example

7.1 Create a JSP File

Create hello.jsp:

<%@ page contentType="text/html; charset=UTF-8" %>
<html>
<body>
<h2>Hello JSP!</h2>

<%
    String name = request.getParameter("name");
    if (name == null) name = "Guest";
%>

<p>Welcome, <%= name %></p>
</body>
</html>


7.2 Access the Page

http://localhost:8080/project-name/hello.jsp?name=John

This example demonstrates how JSP dynamically generates content based on user input.



8. Custom Tags in JSP

What Are Custom Tags?

Custom tags allow developers to define reusable UI components and logic without writing Java code inside JSP pages.

Advantages:

  • Cleaner JSP code

  • Better separation of concerns

  • Improved maintainability

Custom tags are created using Tag Handler classes or Tag Files.



9. JSTL (JavaServer Pages Standard Tag Library)

9.1 What Is JSTL?

JSTL is a collection of standard tags that simplify common tasks such as:

  • Conditional logic

  • Iteration

  • URL management

  • Internationalization


9.2 Core JSTL Example

<c:if test="${not empty username}">
    <p>Hello, ${username}</p>
</c:if>

<c:forEach var="item" items="${items}">
    <p>${item}</p>
</c:forEach>


9.3 Benefits of JSTL

  • Eliminates scriptlets

  • Improves readability

  • Encourages MVC architecture



10. JSP Best Practices

  • Avoid scriptlets whenever possible

  • Use JSTL and Expression Language (EL)

  • Keep JSP focused on presentation only

  • Use servlets or controllers for business logic

  • Modularize JSP using includes and tag files



11. JSP vs Modern Frameworks

While JSP is powerful, modern frameworks:

  • Provide better architecture

  • Reduce boilerplate code

  • Improve testability


However, understanding JSP helps developers:

  • Maintain legacy systems

  • Understand MVC patterns

  • Learn how frameworks work internally



12. Conclusion

JSP is a foundational technology in Java web development that simplifies the creation of dynamic web pages. 

By combining HTML with Java-based server logic, JSP allows developers to build flexible and maintainable web applications.

Although modern frameworks abstract much of JSP’s complexity, mastering JSP concepts—such as directives, scripting elements, custom tags, and JSTL—provides valuable insight into how Java web applications operate behind the scenes. 

This knowledge remains highly relevant for enterprise development and long-term career growth in Java.

Popular posts from this blog

The Early Search Engines: Yahoo, AltaVista, and the Dawn of Web Discovery

Image
The Early Search Engines: Yahoo, AltaVista, and the Dawn of Web Discovery When the World Wide Web first became public in the early 1990s, it was a chaotic digital landscape — thousands of pages scattered across servers around the world, with no easy way to find what you were looking for.  There were no smart algorithms, no Google, and no social media recommendations.  To explore the growing web, users needed a way to search it.  That’s where the first search engines came in.  Among them, Yahoo! and AltaVista were the pioneers that shaped how people discovered information online and laid the foundation for the search-dominated internet we use today. 1. The Problem of Finding Information on the Early Web In the early 1990s, the World Wide Web was growing rapidly.  What began as a small collection of research and university websites quickly expanded into thousands of public pages.  But unlike libraries, the web had no index or directory system.  Us...
Read more

The Birth of Internet Cafes and Online Communities

Image
The Birth of Internet Cafes and Online Communities The late 20th century marked a revolution in human communication.  The internet, once confined to research labs and universities, began spreading into homes, schools, and cities across the globe.  But before every household had Wi-Fi or smartphones, there was another space where people first experienced the digital world together — the Internet Cafe .  At the same time, online communities emerged, connecting people through shared interests, conversations, and digital friendships.  Together, these two phenomena laid the cultural and social foundation of the modern connected world. 1. The Rise of the Internet Cafe: A Gateway to the Digital World In the early 1990s, personal computers and internet connections were still expensive and not widely available.  For many, the first experience of going online didn’t happen at home but in a small, bustling space filled with computers — the Internet Cafe . The world’s ...
Read more

How Hyperlinks Changed the World

Image
How Hyperlinks Changed the World When we think about the internet, we often picture web pages, social media platforms, or search engines.  Yet, one of the most transformative inventions behind all of these is something so simple that we almost take it for granted: the hyperlink .  This seemingly small innovation—blue underlined text that connects one document to another—became the foundation of how we navigate the web.  It not only changed the way we access information but also reshaped communication, education, business, and even the way we think. 1. The Origins of the Hyperlink Idea The concept of linking information predates the modern web by several decades.  The first visionary to describe a system resembling hyperlinks was Vannevar Bush , an American engineer and science administrator.  In his 1945 essay “As We May Think” , Bush described a theoretical machine called the Memex , which would allow users to store books, records, and communications, and to...
Read more