Web.xml

References:-

http://download.oracle.com/docs/cd/E13222_01/wls/docs81/webapp/web_xml.html

This file is used to define each servlet and JSP page inside a web-application.

It is found in WEB-INF directory under the document root of the web application.

It is also called Deployment Descriptor

Context parameters are accessible to any servlet or JSP in the web-app and can be accessed through ServletContext object.

String value = getServletContext().getInitParameter("name_of_context_initialization_parameter");

For springs Context param name for

    application context is  "contextConfigLocation" with value "*.xml"

    log4j is "log4jConfigLocation" with value "*.properties"

    applicationContext.xml is an XML file having the context parameters

Init parameters are specific to a particular servlet and and can be accessed through ServletConfig object.

String value = getServletConfig().getInitParameter("name_of_context_initialization_parameter");

load-on-startup gives the order in which the servlet will initialize

<?xml version="1.0" encoding="ISO-8859-1"?>

<!DOCTYPE web-app

    PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"

    "http://java.sun.com/dtd/web-app_2_3.dtd">

<web-app>

    <display-name>The name of the application </display-name>

    <description>Description of Application</description>

    <welcome-file-list>

           <welcome-file>index.jsp</welcome-file>

    </welcome-file-list>

    <context-param>

     <description>Description of parameter</description>

     <param-name>name_of_context_initialization_parameter</param-name>

     <param-value>value_of_context_initializtion_parameter</param-value>

    </context-param>

 //In case of Servlets , we define our own Servlet classes and corresponding mappings are given  in web.xml

    <servlet>

     <servlet-name>guess_what_name_of_servlet</servlet-name>

     <description>Again, some description</description>

     <servlet-class>com.foo-bar.somepackage.TheServlet</servlet-class>

     <init-param>

       <param-name>foo</param-name>

       <param-value>bar</param-value>

     </init-param>

     <load-on-startup>1</load-on-startup>

    </servlet>

    <servlet-mapping>

     <servlet-name>name_of_a_servlet</servlet-name>

     <url-pattern>*.some_pattern</url-pattern>

    </servlet-mapping>

 //In case of struts 2 , we define the filters and corresponding mapping of FilterDispatcher in web.xml

   <filter>

      <filter-name>struts2</filter-name>

      <filter-class>

         org.apache.struts2.dispatcher.FilterDispatcher

      </filter-class>

   </filter>

   <filter-mapping>

      <filter-name>struts2</filter-name>

      <url-pattern>/*</url-pattern>

   </filter-mapping>

//In case of springs, we define the servlet and  corresponding mapping of Dispatcher Serv

    <servlet>

        <servlet-name>employee</servlet-name>

        <servlet-class>org.springframework.web.servlet.DispatcherServlet </servlet-class>

        <load-on-startup>1</load-on-startup>

    </servlet>

    <servlet-mapping>

        <servlet-name>employee</servlet-name>

        <url-pattern>/</url-pattern>

    </servlet-mapping>

    <context-param>

        <param-name>contextConfigLocation</param-name>

        <param-value>/WEB-INF/employee-servlet.xml</param-value>

    </context-param>

    <session-config>

     <session-timeout>30</session-timeout>

    </session-config>

</web-app>