Servlet Tutorial

• Servlet Tutorial
• Servlet Environment Settings
• Servlet Life Cycle
• Servlet Example
• Servlet Form Data
• Servlet Client HTTP Request
• Servlet Server HTTP Response
• Servlet HTTP Status Codes
• Servlet Filter
• Servlet Exception Handling
• Servlet Cookie Handling
• Servlet Session Tracking
• Servlet Database Access
• Servlet File Upload
• Servlet Processing Date
• Servlet Web Page Redirection
• Servlet Hit Counter
• Servlet Auto Refresh Page
• Servlet Send Email
• Servlet Package
• Servlet Debugging
• Servlet Internationalization

Servlet Example

Let's create a basic example of a Java Servlet.

In this example, we'll create a simple "Hello, World!" Servlet. This Servlet will respond to HTTP GET requests by sending back a message saying "Hello, World!"

1. Create a new Servlet class

First, you need to create a new class that extends HttpServlet:

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;

public class HelloWorldServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        // Set the response content type
        response.setContentType("text/html");

        // Get the printwriter object from response to write the required html in the response
        PrintWriter out = response.getWriter();

        out.println("<h1>" + "Hello, World!" + "</h1>");
    }
}

In this Servlet, the doGet() method is overridden to handle HTTP GET requests. The response.setContentType("text/html") call sets the response content type to be HTML, and response.getWriter() gets a PrintWriter that can be used to send output to the client. Finally, out.println("<h1>" + "Hello, World!" + "</h1>"); writes an HTML heading with the text "Hello, World!" to the response.

2. Configure the Servlet

Next, you need to configure your Servlet. This can be done using annotations or by modifying the web.xml deployment descriptor.

Using annotations:

import javax.servlet.annotation.WebServlet;
//...

@WebServlet("/hello")
public class HelloWorldServlet extends HttpServlet {
    //...
}

In this example, @WebServlet("/hello") specifies that this Servlet should handle requests to the "/hello" URL.

Using web.xml:

<web-app>
    <servlet>
        <servlet-name>HelloWorldServlet</servlet-name>
        <servlet-class>com.example.HelloWorldServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>HelloWorldServlet</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>
</web-app>

In this example, a <servlet> element is used to declare the Servlet, and a <servlet-mapping> element is used to map the Servlet to the "/hello" URL.

3. Run the Servlet

Finally, you need to compile your Servlet and run it in a Servlet container, such as Apache Tomcat or Jetty.

Once your Servlet is running, you should be able to visit http://localhost:8080/hello (assuming your Servlet container is running on port 8080) in your web browser and see "Hello, World!" displayed on the page.