Java(TM) Boutique - Stepping through Jakarta Struts -

Tutorials : Stepping through Jakarta Struts :

Step 1: The directories and files of a Struts application

You'll need to know the directory structure of a Struts application, and what's put in the directories. The "struts-blank" application is well-suited for this presentation, since it contains a minimum number of files:

- Figure 3: The Struts directory structure -

File or Directory name	Purpose
META-INF	Contains meta information. Used by utilities etc.
WEB-INF/classes	This is where you place you own Java classes.
WEB-INF/classes/ApplicationResources.properties	Contains the messages (fixed texts) of the application. Error messages are also put here.
WEB-INF/lib/struts.jar	Contains the Struts servlet, helper classes, taglib code etc.
WEB-INF/*.tld	The Struts tag libraries.
WEB-INF/struts-config.xml	A Struts configuration file. More on this later.
WEB-INF/web.xml	The usual configuration file for the servlet container. More on this later.
index.jsp	The jsp-files (and html-files) may be placed in the root of the application directory. "struts-blank" contains this single jsp-file.

- Table 1: The files and directories in a Struts application -

Step 2: Starting on a new Struts application

The easiest way to start on a new Struts application is to take an existing one--for example "struts-blank"--and make a copy of it in the "webapps" directory. When you get more experienced with Struts you'll probably add your own standard classes and files to your setup, and you'd then start taking a copy of this directory structure. For our first application we simply copy all files and directories in the folder "struts-blank" and rename the folder to "myproject". The contents of some of the files must now be edited.

Step 3: The web.xml file

The web.xml file is where servlets and other stuff are defined to the servlet container. We'll remove some unnecessary things from the web.xml file so it looks like this:

<?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">

<web-app>

  <!-- Standard Action Servlet Configuration (with debugging) -->
  <servlet>
    <servlet-name>action</servlet-name>
    <servlet-class>
	  org.apache.struts.action.ActionServlet
	</servlet-class>
    <init-param>
      <param-name>application</param-name>
      <param-value>ApplicationResources</param-value>
    </init-param>
    <init-param>
      <param-name>config</param-name>
      <param-value>/WEB-INF/struts-config.xml</param-value>
    </init-param>
    <init-param>
      <param-name>debug</param-name>
      <param-value>2</param-value>
    </init-param>
    <init-param>
      <param-name>detail</param-name>
      <param-value>2</param-value>
    </init-param>
    <init-param>
      <param-name>validate</param-name>
      <param-value>true</param-value>
    </init-param>
    <load-on-startup>2</load-on-startup>
  </servlet>

 
  <!-- Standard Action Servlet Mapping -->
  <servlet-mapping>
    <servlet-name>action</servlet-name>
    <url-pattern>*.do</url-pattern>
  </servlet-mapping>

 
  <!-- Struts Tag Library Descriptors -->
  <taglib>
    <taglib-uri>/WEB-INF/struts-bean.tld</taglib-uri>
    <taglib-location>/WEB-INF/struts-bean.tld</taglib-location>
  </taglib>

  <taglib>
    <taglib-uri>/WEB-INF/struts-html.tld</taglib-uri>
    <taglib-location>/WEB-INF/struts-html.tld</taglib-location>
  </taglib>

  <taglib>
    <taglib-uri>/WEB-INF/struts-logic.tld</taglib-uri>
    <taglib-location>/WEB-INF/struts-logic.tld</taglib-location>
  </taglib>

</web-app>

- Figure 4: The web.xml file -

The file contains three sections:

the definition of the Struts servlet named "ActionServlet"
the URL mapping for the calls to this servlet
the definitions of the Struts tag libraries

You'll see that the servlet will be called if our browser requests a file called <some-name>.do. So when we submit the form in our one-page application we'll decide to use the action-name "submit.do". How the Struts servlet knows what to do with this request we'll discover next.

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