Java Servlet

Java Servlet technology provides Web developers with a simple, consistent mechanism for extending the functionality of a Web server and for accessing existing business systems. Servlets are server-side Java EE components that generate responses (typically HTML pages) to requests (typically HTTP requests) from clients. A servlet can almost be thought of as an applet that runs on the server side—without a face.

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

public class Hello extends GenericServlet {
   public void service(ServletRequest request, ServletResponse response)
           throws ServletException, IOException {
      response.setContentType("text/html");
      final PrintWriter pw = response.getWriter();
      pw.println("Hello, world!");
      pw.close();
  }
}