How do I create a basic servlet using the HttpServlet class?

By I Wayan Saryada in Servlet 0 Comment

To create a basic servlet using the HttpServlet class in Jakarta Servlet API, follow these steps:

Steps to Create a Basic Servlet:

  1. Create a Java Class Extending HttpServlet:
    • Your servlet class should extend the HttpServlet class provided in the Jakarta Servlet API.
  2. Define Servlet Annotations or Configuration:
    • Use the @WebServlet annotation to define the servlet and map it to a URL pattern. Alternatively, you can configure it in the web.xml file if annotations are not used.
  3. Override doGet or doPost Methods:
    • Override doGet for handling GET requests and doPost for POST requests (based on the type of request you expect).
  4. Set the Content Type in Response:
    • The response content type can be set using response.setContentType().
  5. Write the Response to Output:
    • Use a PrintWriter object received from response.getWriter() to write the response content.

Code Example:

Here’s a sample implementation for a basic servlet:

package org.kodejava.servlet;

import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "HelloWorldServlet", urlPatterns = {"/hello", "/helloworld"})
public class HelloWorld extends HttpServlet {

   @Override
   protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
      response.setContentType("text/html");

      PrintWriter writer = response.getWriter();
      writer.println("<html>");
      writer.println("<head><title>Hello World Servlet</title></head>");
      writer.println("<body>Hello World! How are you doing?</body>");
      writer.println("</html>");
      writer.close();
   }
}

Explanation of Code:

  1. @WebServlet Annotation:
    • name: Specifies the servlet name.
    • urlPatterns: Maps the servlet to specific URL patterns (in this example, /hello).
  2. doGet Method:
    • Handles GET requests sent to /hello.
    • Sets the content type for the response to text/html so that the client knows the returned content is HTML.
    • Dynamically writes an HTML page to the response using the PrintWriter.
  3. Response Lifecycle:
    • Any request to http://<server>:<port>/hello is routed to the doGet method based on the @WebServlet mapping.

Deploying the Servlet in Jakarta EE:

  • Place your servlet class in the Java package structure under src/main/java.
  • Ensure your project is configured to use a Jakarta Servlet container like Apache Tomcat or Jakarta EE compatible application server.
  • Deploy the .war file or run directly if your IDE supports it.

To build the .war file you can follow in steps in this post: How to build WAR file for Jakarta EE Servlet Container?.

Maven dependencies

<dependency>
    <groupId>jakarta.servlet</groupId>
    <artifactId>jakarta.servlet-api</artifactId>
    <version>6.1.0</version>
    <scope>provided</scope>
</dependency>

Maven Central