Framing multiple servlet request url pattern

Question

I am using servlet to get request from frontend. Am i able to make single servlet which could do multiple operation based on url pattern? Here will be my url mapping

<servlet>
<servlet-name>Hello</servlet-name>
<servlet-class>HelloWorld</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>Hello</servlet-name>
<url-pattern>/HelloServlet</url-pattern>
<url-pattern>/HelloServletOne</url-pattern>
<url-pattern>/HelloServletTwo</url-pattern>
</servlet-mapping>

That means if i hit to the url as framed below it should invoke its own functionalities.

• URL:/HelloServlet: it should do function 1
• URL:/HelloServletOne: it should do function 2
• URL:/HelloServletTwo: it should do function 3 etc.

How can i achive this by extending servlet.?
Code/link examples are much appreciated.

Answer 1

Regarding your url-pattern you need to know what URL was called. Because a request can be made due to different http-methods (GET, POST etc.) you can use parts of the FrontController Pattern

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 HelloServlet extends HttpServlet {

  private static final String SERLVET = "HelloServlet";
  private static final String SERLVET_ONE = "HelloServletOne";
  private static final String SERLVET_TWO = "HelloServletTwo";

  @Override
  protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    processRequest(req, resp);
  }

  @Override
  protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    processRequest(req, resp);
  }

  private void processRequest(HttpServletRequest req, HttpServletResponse resp) {
    String path = req.getServletPath();
    switch (path) {
      case SERLVET:
        // ... call your function1
        break;
      case SERLVET_ONE:
        // ... call your function2
        break;

      case SERLVET_TWO:
        // ... call your function3
        break;
      default:
        break;
    }

    // do something else
  }

}

The getServletPath method may only work for explicit url-patterns like you have given. For other information on the URL check this link