Manually Creating a Simple Web ARchive (WAR) File

• The static HTML files and JSPs are stored in the top level directory.
• The Servlet and related Java[tm] technology class files must be stored in the WEB-INF/classes directory.
• Any auxiliary library JAR files must be stored in the WEB-INF/lib directory.
• The deployment descriptor is stored as a file named web.xml in the WEB-INF directory.

The following is the mandatory header of the web.xml document. This defines the document as an XML file and relates the syntax of the file to the DOCTYPE resource specified.

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE web-app
    PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN"
    "http://java.sun.com/j2ee/dtds/web-app_2_2.dtd">

Servlets

The simplest form of deployment descriptor that is needed to deploy a Java[tm] Servlet is as follows (assumes the header is preceding):

<web-app>
    <servlet>
        <servlet-name>HelloServlet</servlet-name>
        <servlet-class>mypackage.HelloServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>HelloServlet</servlet-name>
        <url-pattern>/HelloServlet</url-pattern>
    </servlet-mapping>
</web-app>

The <servlet-name> element is how the Servlet is known within the XML file, the <servlet-class> is the fully qualified Java programming language class name of the Servlet; this Java programming language class needs to be located in the WEB-INF/classes directory. Thus, for the previous example this would be reflected in the directory structure: WEB-INF/classes/mypackage/HelloServlet.class.

The <url-pattern> is how the Servlet is referenced from a Universal Resource Indicator(URI) - see the "Accessing the Content" section of this article.  According to the Servlet specification it is recommended that you include a mapping to avoid any potential issues. All of these elements are documented in the Servlet specifications.

Note: The structure of the elements must follow the order in the DTD definition. For example all <servlet>s must be defined before any <servlet-mapping>s can be specified.

JSPs

JSPs can be deployed in a WAR file in three ways:

1. Without reference in web.xml
   
   

   You can put your JSPs directly in the root of the WAR file; the container will recognise the .jsp extension.
   

2. Precompiling
   
   

   By precompiling the JSP, you have a Servlet.  You can reference the JSP's compiled class (Servlet) and also locate the class as in the example from the "Servlets" section of this article. However, the <url-pattern> could be something like Foo.jsp, to signify that it is/was a JSP. For more information, see the JSP Specification note in the References section of this article.
   

3. Referencing
   
   You can reference the JSP file in web.xml; by using the example in the "Servlets" section and replacing <servlet-class> with <jsp-file>.  In this case the <jsp-file> root is the root of the WAR file, unlike the Servlet scenario.