Configuring Welcome File List for a Java EE Web Application

We can configure a set of default file names to be loaded when request is made to a directory path using the DDs <welcome-file-list> element. Each file can be put inside a <welcome-file> element. The file can be a servlet mapping path, a jsp or even a static html file.

Whenever a request is received for a directory path (e.g. /mypath/), all the file names declared inside <welcome-file> sub-element of the <welcome-file-list> element in DD are appended to the path in the order they are defined in the <welcome-file-list> element. If a valid resource is found after appending (e.g. /mypath/myservlet), the resource is returned; else an error message (404 or directory listing error message).

Note that the trailing / after path (e.g. /mypath/) denotes that it is looking for a directory. If the trailing / is not present, then it is taken as a direct resource request and hence the welcome files are not appended to the path.

 

Try-It-Out Example

Create a servlet MyServlet mapped with a url-pattern "/MyServlet".

Print some statements inside doGet to make sure it is called.

 

Now deploy, restart and execute the web application without specifying any resource (but only web application context) like:

http://localhost:8080/ServletTraining/

If you are practicing in eclipse, you can right click on the project and then say run on server.

 

Now you should get an error as below:

HTTP Status 404 - /ServletTraining/

type Status report

message /ServletTraining/

description The requested resource is not available.

Apache Tomcat/8.0.20

 

Next modify the web.xml to add the servlet’s path to the <welcome-file-list> element as:

<welcome-file-list>

    <welcome-file>MyServlet</welcome-file>

  </welcome-file-list>

Now deploy, restart and execute the web application without specifying any resource (but only web application context) like:

http://localhost:8080/ServletTraining/

If you are practicing in eclipse, you can right click on the project and then say run on server.

 

You can see that the servlet gets executed this time without any exception.

 

Next change the servlet’s mapping to "/SomePath/MyServlet" and try executing specifying the path as:

http://localhost:8080/ServletTraining/SomePath/

Note that you would not have been successful if you execute this as:

http://localhost:8080/ServletTraining/SomePath

 

Complete Codes

MyServlet.java

package com.javajee.servlets;

import java.io.IOException;

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("/MyServlet")
public class MyServlet extends HttpServlet {
  private static final long serialVersionUID = 1L;

  public MyServlet() {
    super();
  }

  protected void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {

    System.out.println("/MyServlet");
  }

}

 

Web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://xmlns.jcp.org/xml/ns/javaee"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
    id="WebApp_ID" version="3.1">
    <display-name>ServletTraining</display-name>
    <welcome-file-list>
        <welcome-file>MyServlet</welcome-file>
    </welcome-file-list>
</web-app>

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