How to Build Web Applications in Java? Servlet and JSP Tutorial

Java is a widely used programming language that has found its way into numerous application domains, including web development. Servlets and JavaServer Pages (JSP) are two fundamental technologies that form the backbone of Java-based web applications. In this article, we will explore the essentials of Java servlet and JSP tutorial, the Servlet life cycle, and the steps to create Servlets.

We will also compare Servlets and JSP, explore the JSP scripting elements, and discuss how to build web applications in Java. But before starting the preparation regarding swapping, consider learning these Java certification courses.

Introduction to Servlets

Servlets are Java classes used to extend the capabilities of a web server. They enable the server to respond to client requests, typically in the form of HTTP requests. Java Servlet tutorial are a key component of Java EE (Enterprise Edition) and are widely employed for building dynamic web applications. They are known for their platform independence, security, and portability.

Servlet Life Cycle

The Servlet life cycle is a fundamental concept in Java web development, which undertakes from its initialisation to handling client requests and, ultimately, its termination. Understanding the Servlet life cycle is essential for developers who seek to build dynamic web applications using Servlet technology. Servlets have a well-defined life cycle, which consists of the following stages:

• Initialisation: During this stage, the servlet is loaded into memory and initialised. This happens when the web server starts or when the first request for the servlet is received.

• Service: The service() method is invoked to process client requests. This method handles multiple types of HTTP requests, such as GET, POST, PUT, DELETE.

• Request Handling & Processing : For each request, a new thread is created, and the service method is invoked. This method takes ServletRequest and ServletResponse as parameters.Then the method delegates the request to doGet, doPost, doPut, doDelete depending on the HTTP method.

• Destruction: The servlet is destroyed and removed from memory when the web server is shut down or when it is no longer needed.

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Key Characteristics of Servlets

Servlets is a fundamental component of Java-based web development, and possess a distinctive set of key characteristics that make them a preferred choice for building dynamic web applications. Their platform independence, inherent security features, and portability enable developers to seamlessly process client requests and generate responses in a secure, reliable, and versatile manner. The following are the key characteristics of Servlets:

• Platform Independence: Servlets are platform-independent, making them suitable for a variety of web servers.

• Security: Java's built-in security features make Servlets a reliable choice for web applications.

• Portability: Servlets can run on different web servers without modification.

Steps to Create Servlets

Creating Servlets is an essential skill in Java web development, allowing developers to build dynamic web applications that can respond to client requests effectively. Therefore, it is important to understand the fundamental steps required to create Servlets. These steps encompass the development of Java classes, configuring deployment descriptors, and deploying your Servlet within a web application, making it accessible to users through web browsers.Thus, Creating a basic Servlet involves the following steps:

• Create a Java class: Define a Java class that extends the HttpServlet class or implements the Servlet interface.

• Override doGet() or doPost() methods: Implement these methods to handle HTTP GET or POST requests.

• Compile the servlet: Compile the Java class using a Java compiler.

• Configure in the deployment descriptor: Add an entry for the servlet in the web application's deployment descriptor (web.xml).

• Deploy the web application: Deploy the web application on a servlet container like Apache Tomcat.

• Access the servlet: Access the servlet using its URL from a web browser.

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Java Servlets Examples

Java Servlets are a fundamental part of Java-based web applications. They are used to handle HTTP requests and generate dynamic web content. Here is a basic Java Servlet example to get you started:

1. Create a Java Servlet Class:

First, you need to create a Java class that extends javax.servlet.http.HttpServlet and override the doGet or doPost method to handle HTTP requests.

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class MyServlet extends HttpServlet {

protected void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

// Your code to handle GET requests

response.getWriter().println("Hello, World!");

}

}

2. Web Deployment Descriptor (web.xml):

To map the servlet to a URL, you need to configure your servlet in the web.xml file.

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd">

<servlet>

<servlet-name>MyServlet</servlet-name>

<servlet-class>com.example.MyServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>MyServlet</servlet-name>

<url-pattern>/hello</url-pattern>

</servlet-mapping>

</web-app>

3. Web Application Structure:

Your web application structure might look something like this:

/WEB-INF

/classes

/com

/example

MyServlet.class

web.xml

MyServlet.java

4. Build and Deploy: Build your web application (e.g., using Apache Maven) and deploy it to a servlet container such as Apache Tomcat.

Introduction to JSP

Introduction to JSP in Java is yet another of the most fundamental concepts when it comes to Java sample web applications in Java. JavaServer Pages (JSP) is another technology used for web development. Unlike Servlets, JSP allows embedding Java code directly into the HTML markup, making it easier for developers to create dynamic web pages. JSP files have a .jsp extension and are compiled into Servlets by the server.

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Key Characteristics of JSP

JavaServer Pages (JSP) is a versatile technology that revolutionises web development in Java. It boasts a set of key characteristics that make it a popular choice for building dynamic web applications. JSP offers simplicity, ease of maintenance, and seamless integration of Java code within HTML, allowing developers to create interactive and user-friendly web pages.

• Simplicity: JSP allows developers to create dynamic web pages using a combination of HTML and Java code.

• Ease of Maintenance: JSP separates the presentation layer from the business logic, making it easier to maintain and update web applications.

• Integration: JSP and Servlets can seamlessly work together in a web application, with Servlets handling the back-end logic and JSP managing the user interface.

Java JSP Servlet Example

JavaServer Pages (JSP) is a technology used for building dynamic web pages in Java web applications. When used in conjunction with Java Servlets, it can create powerful and interactive web applications. Below is a simple Java JSP Servlet example:

1. Create a JSP Page:

Create a JSP file, for example, hello.jsp, which will be responsible for rendering the dynamic content.

<!DOCTYPE html>

<html>

<head>

<title>Hello JSP Example</title>

</head>

<body>

<h1>Hello, <%= request.getAttribute("name") %>!</h1>

</body>

</html>

In this JSP, we are using <%= request.getAttribute("name") %> to display the value of the "name" attribute.

2. Create a Java Servlet:

Create a Java Servlet that will process the request and set attributes for the JSP to use.

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

@WebServlet("/HelloServlet")

public class HelloServlet extends HttpServlet {

protected void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

String name = "John"; // You can retrieve this value from a database or other sources

request.setAttribute("name", name);

request.getRequestDispatcher("hello.jsp").forward(request, response);

}

}

In this example, the servlet sets an attribute called "name" and forwards the request to the hello.jsp page, where it will be displayed.

3. Web Deployment Descriptor (web.xml):

If you are not using annotations, you will need to configure the servlet and URL mapping in the web.xml file as shown in the previous example.

4. Web Application Structure:

Your web application structure might look like this:

/WEB-INF

/classes

HelloServlet.class

web.xml

hello.jsp

5. Build and Deploy:

Build your web application and deploy it to a servlet container such as Apache Tomcat.

JSP vs Servlets

Servlets and JSP serve different purposes in web development. Servlets are used for processing requests and implementing business logic, while JSP is primarily for creating dynamic web pages. They can work together in a web application, with Servlets handling the business logic and JSP handling the presentation layer.

JSP Scripting Elements

JavaServer Pages (JSP) scripting elements are a fundamental part of JSP technology, enabling web developers to seamlessly integrate Java code into the HTML markup of web pages. These elements provide a powerful and flexible means to create dynamic, data-driven web applications.

By allowing Java code to be embedded within JSP documents, developers can access and manipulate data, perform computations, and generate content on the server-side, resulting in interactive and responsive web interfaces.

JSP scripting elements come in various forms, including declarations, scriptlets, and expressions, each serving a unique purpose in building dynamic web applications that combine the strengths of Java and HTML. The primary JSP scripting elements include:

• Declaration: <%! ... %> - Used to declare variables and methods.

• Scriptlet: <% ... %> - Used to write Java code within the JSP.

• Expression: <%= ... %> - Used to evaluate and display the result of a Java expression within the HTML.

JSP Request and Response

JSP can handle HTTP requests and responses such as Servlets. You can access request parameters, session data, and respond to client requests in a JSP using implicit objects like request, response, session, and out.

How to Build Web Applications in Java using Servlet and JSP

Understanding how to create web applications in Java using Servlet and JSP is a dynamic and powerful approach to web development. Java, known for its platform independence and security, provides a solid foundation for creating interactive and feature-rich web experiences. Servlets handle the back-end logic, processing client requests, while JavaServer Pages (JSP) seamlessly blend HTML with Java code to create dynamic and responsive user interfaces.

Here is a step-by-step servlet and JSP Tutorial guide on how to build a web application using Java Servlets and JSP, This guide also involves web application in Java example which will help students clearly understand the fundamentals behind building web applications in Java:

• Set up your development environment: Install a Java Development Kit (JDK), an Integrated Development Environment (IDE) such as Eclipse or IntelliJ, and a Servlet container like Apache Tomcat.

• Create a dynamic web project: In your IDE, create a dynamic web project and configure the deployment descriptor (web.xml).

• Write Servlets: Create Servlet classes to handle different aspects of your web application, such as user registration, login, or data retrieval.

• Write JSP pages: Create JSP pages to display the web interface. Write your JSP code using a combination of HTML and Java code. Java code in JSP is enclosed in <% %> tags.

• Integrate Servlets and JSP: Use Servlets to process requests, perform business logic, and interact with databases. Render dynamic content in JSP pages by embedding Java code.

• Deploy your application: Deploy your web application to the servlet container (e.g., Tomcat).

• Test your application: Access your web application through a web browser and test its functionality.

• Debug and refine: Use the debugging tools provided by your IDE to identify and fix any issues in your Servlets and JSP pages.

• Optimise and secure: Optimise your code for performance and ensure that your web application is secure from common web application vulnerabilities.

• Scale and maintain: As your web application grows, consider scalability and maintenance, such as database optimisation, load balancing, and security updates.

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Conclusion

Introduction to Servlets and JSP are fundamental technologies for building dynamic web applications in Java. By understanding their life cycle, scripting elements, and integration, you can create powerful and feature-rich web applications. Following these steps on web-based application of Servlet and JSP Tutorial example will help you build your own web applications using Servlets and JSP, and explore the endless possibilities of becoming a proficient Java programmer.