Build a Temperature Converter Maven Web Application Using Java,Â
Temperature conversion is a common utility in many applications. In this tutorial, we’ll create a simple Maven-based web application that converts temperatures between Celsius, Fahrenheit, and Kelvin using Java, JSP, and EJB.
Step 1: Prerequisites
Before starting, ensure you have the following installed:
- Java Development Kit (JDK)
- Apache Maven
- Apache Tomcat Server
- An IDE like Eclipse or IntelliJ IDEA
Step 2: Set Up the Maven Project
- Open your IDE and create a new Maven project.
- Update the
pom.xmlfile with the required dependencies:
<dependencies>
<dependency>
<groupId>javax</groupId>
<artifactId>javaee-api</artifactId>
<version>8.0</version>
<scope>provided</scope>
</dependency>
</dependencies>
Step 3: Create the Project Structure
Organize the project as follows:
src/main/java
└── com.example.temperature
├── ConverterEJB.java
└── ConverterServlet.java
src/main/webapp
└── WEB-INF
└── web.xml
└── index.jsp
Step 4: Develop the Backend Logic
1. Create the EJB (ConverterEJB)
package com.example.temperature;
import javax.ejb.Stateless;
@Stateless
public class ConverterEJB {
public double toCelsius(double fahrenheit) {
return (fahrenheit - 32) * 5 / 9;
}
public double toFahrenheit(double celsius) {
return (celsius * 9 / 5) + 32;
}
public double toKelvin(double celsius) {
return celsius + 273.15;
}
}
2. Create the Servlet (ConverterServlet)
package com.example.temperature;
import java.io.IOException;
import javax.inject.Inject;
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("/convert")
public class ConverterServlet extends HttpServlet {
@Inject
private ConverterEJB converter;
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
double input = Double.parseDouble(request.getParameter("temperature"));
String scale = request.getParameter("scale");
double result = 0;
switch (scale) {
case "Celsius":
result = converter.toCelsius(input);
break;
case "Fahrenheit":
result = converter.toFahrenheit(input);
break;
case "Kelvin":
result = converter.toKelvin(input);
break;
}
request.setAttribute("result", result);
request.setAttribute("scale", scale);
request.getRequestDispatcher("index.jsp").forward(request, response);
}
}
Step 5: Create the Frontend
1. Configure web.xml
<web-app>
<servlet>
<servlet-name>ConverterServlet</servlet-name>
<servlet-class>com.example.temperature.ConverterServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ConverterServlet</servlet-name>
<url-pattern>/convert</url-pattern>
</servlet-mapping>
</web-app>
2. Design index.jsp
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Temperature Converter</title>
</head>
<body>
<h1>Temperature Converter</h1>
<form action="convert" method="post">
<label for="temperature">Enter Temperature:</label>
<input type="number" id="temperature" name="temperature" required>
<label for="scale">Convert To:</label>
<select id="scale" name="scale">
<option value="Celsius">Celsius</option>
<option value="Fahrenheit">Fahrenheit</option>
<option value="Kelvin">Kelvin</option>
</select>
<button type="submit">Convert</button>
</form>
<c:if test="${not empty result}">
<h2>Converted Temperature: ${result} ${scale}</h2>
</c:if>
</body>
</html>
Step 6: Deploy and Run
- Package the project into a WAR file:
mvn clean package
- Deploy the WAR file to your Tomcat server.
- Start the server and open your browser at
http://localhost:8080/temperature-converter.
Step 7: Test the Application
Enter a temperature value, select the target scale (Celsius, Fahrenheit, or Kelvin), and click “Convert.” The converted value will be displayed on the page.