JEE: deployment descriptor

Web XML

In the deployment descriptor (web.xml file), typically contained at WebContent/WEB-INF/web.xml, you can modify the servlet mapping:

 <?xml version="1.0" encoding="UTF-8"?>  
 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
      xmlns="http://java.sun.com/xml/ns/javaee"  
      xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"  
      id="WebApp_ID" version="3.0">  

      <display-name>HelloWorldServlet</display-name> 
 
      <servlet>  
           <servlet-name>XYZ</servlet-name>  
           <servlet-class>com.swtk.web.servlets.HelloWorld</servlet-class>  
      </servlet>  

      <servlet-mapping>  
           <servlet-name>XYZ</servlet-name>  
           <url-pattern>/hiddenservlets/helloworld.do</url-pattern>  
      </servlet-mapping>  

      <welcome-file-list>  
           <welcome-file>index.html</welcome-file>  
           <welcome-file>index.htm</welcome-file>  
           <welcome-file>index.jsp</welcome-file>  
           <welcome-file>default.html</welcome-file>  
           <welcome-file>default.htm</welcome-file>  
           <welcome-file>default.jsp</welcome-file>  
      </welcome-file-list>  

 </web-app>

The first part of the deployment descriptor is the creation of the servlet node:

 <servlet>  

      <!-- this is a variable name that could be anything -->
      <servlet-name>XYZ</servlet-name>  

      <!-- this is a fully qualified mapping to the servlet class -->
      <servlet-class>com.swtk.web.servlets.HelloWorld</servlet-class>  

 </servlet>

The second part of the descriptor contains the servlet-mapping:

 <servlet-mapping>  
      
      <!-- refer to the variable name in the servlet node -->
      <servlet-name>XYZ</servlet-name>  
    
      <!-- define a mapping -->
      <url-pattern>/hiddenservlets/helloworld.do</url-pattern>  

 </servlet-mapping>

Multiple url-pattern nodes can be defined in the same servlet-mapping block. The use of the .do extension is a convention from earlier days of web development.

Using Annotations

In Servlets 3.0, you can use annotations directly on the servlet to accomplish the same thing.

 package com.swtk.web.servlets;  

 import java.io.IOException;  
 import java.io.PrintWriter;  
 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(
    description = "Simple HelloWorld Project", 
    urlPatterns = { 
       "/HelloWorld", 
       "/hiddenservlets/helloworld.do" 
    }
 )  

 public class HelloWorld extends HttpServlet {  

      private static final long     serialVersionUID     = 1L;  

      public HelloWorld() {  
           super();  
      }  

      protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {  
           PrintWriter out = response.getWriter();  
           out.print("Hello, World!");  
           out.close();  
      }  
 }

JEE

Friday, December 5, 2014

Servlet Mapping

Web XML

Using Annotations