Introduction to JavaServer Pages (JSP)

Posted Jun 24, 2024

By Alexander Chuev

3 min read

Introduction

JavaServer Pages (JSP) is a technology used for developing web applications based on Java. It allows developers to create dynamic web pages that generate content dynamically and seamlessly integrate Java code into HTML or XML documents. In this article, we will explore the fundamentals of JSP, its architecture, syntax, and practical examples of its usage in web development.

What is JavaServer Pages (JSP)?

JavaServer Pages (JSP) is a technology that enables the creation of web content dynamically. It provides a simplified way to write Java code embedded within HTML or XML pages. JSP pages are compiled into servlets and executed on the server-side to generate dynamic content, which is then sent to the client’s web browser.

Architecture of JSP

JSP Container:
JSP pages are processed by a JSP container (part of the servlet container), which translates JSP pages into servlets during the first request or when changes are detected.
Compilation:
Upon translation, the JSP container compiles the generated servlet into Java bytecode, which is then executed by the Java Virtual Machine (JVM).
Execution:
During runtime, the servlet container manages the execution of servlets generated from JSP pages, handling requests, and generating responses dynamically.

Syntax of JSP

JSP combines HTML or XML markup with Java code using special tags known as JSP tags. These tags allow developers to embed Java code directly within the HTML structure of the page.

Scripting Elements: JSP provides several types of scripting elements to embed Java code within the page:
- Scriptlet (<% … %>)
  1 <% // Java code here %>
- Expression (<%= ... %>)
  1 <%= expression %>
- Declaration (<%! ... %>)
  1 <%! // Variable or method declaration %>
Directives: JSP directives provide instructions to the JSP container about how to process the JSP page during translation and execution:
- Page Directive (<%@ page ... %>)
  1 <%@ page language="java" contentType="text/html; charset=UTF-8" %>
- Include Directive (<%@ include ... %>)
  1 <%@ include file="header.jsp" %>
Actions: JSP actions are XML-based tags that control the behavior of the JSP engine and provide dynamic behavior to the page:
- <jsp:useBean>: Instantiates a JavaBean for use within the JSP page.
- <jsp:setProperty>: Sets properties of a JavaBean.
- <jsp:getProperty>: Retrieves properties of a JavaBean.

Example of a Simple JSP Page

Let’s create a simple JSP page (hello.jsp) that displays a greeting message:

        
      
<%@ page language="java" contentType="text/html; charset=UTF-8" %>
<!DOCTYPE html>
<html>
<head>
    <title>Hello JSP</title>
</head>
<body>
    <h1>Hello, <%= request.getParameter("name") %></h1>
</body>
</html>

In this example:

<%@ page ... %> directive sets the page language and content type.
<%= ... %> expression tag retrieves and displays the name parameter from the request URL query string.

Integrating Java Code in JSP

JSP allows seamless integration of Java code to perform dynamic content generation, database operations, business logic, and more.

        
      
<%@ page import="java.util.*" %>
<!DOCTYPE html>
<html>
<head>
    <title>Dynamic Content</title>
</head>
<body>
    <%
        Date now = new Date();
        out.println("<p>Current date and time: " + now + "</p>");
    %>
</body>
</html>

In this example:

<%@ page import="java.util.*" %> directive imports java.util.Date class.
<% ... %> scriptlet embeds Java code to retrieve the current date and time using Date class.

Advantages of JSP

Simplicity: Allows developers to combine HTML/XML and Java code seamlessly.
Ease of Maintenance: Facilitates easier separation of presentation logic and business logic.
Reusability: Encourages reuse of components and templates across multiple pages.
Integration: Integrates well with Java EE technologies and frameworks.

Conclusion

JavaServer Pages (JSP) is a powerful technology for building dynamic and interactive web applications using Java. By enabling developers to embed Java code within HTML or XML pages, JSP simplifies the process of creating dynamic content and enhances the maintainability of web applications. Understanding the architecture, syntax, and best practices of JSP empowers developers to leverage its capabilities effectively in building robust and scalable web solutions.

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