Application Environment

Application Environment
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Application Environment

While more and more server based frameworks, libraries, standards, and architectures for Java are invented to make programmer's life easier, software deployment seems to get harder and harder. For example, Java Enterprise Beans tried to make creation of persistent and networked objects easy and somewhat automatic, but the number of deployment descriptions got enormous. As IT Mill Toolkit lives in a Java Servlet container, it must follow the rules, but it tries to avoid adding extra complexity.

All IT Mill Toolkit applications are deployed as Java web applications, which can be packaged as WAR files. For a detailed tutorial on how web applications are packaged, we refer to any Java book that discusses Servlets. Sun has excellent reference online on http://java.sun.com/j2ee/tutorial/1_3-fcs/doc/WCC3.html .

Creating Deployable WAR in Eclipse

To deploy the created application to a web server, you need to create a WAR package. Here we give the instructions for Eclipse.

Open project properties and first set the name and destination of the WAR file in Tomcat Export to WAR settings tab. Exporting to WAR is done by selecting Export to WAR from Tomcat Project in project context menu (just click calc with right mouse button on Package contents tree.

Web Application Contents

The following files are required in a web application in order to run it.

Web application organization

WEB-INF/web.xml: This is the standard web application descriptor that defines how the application is organized. You can refer to any Java book about the contents of this file. Also see an example in Example 3.1, “web.xml”.
WEB-INF/lib/itmill-toolkit-4.0.3.jar: This is the IT Mill Toolkit library. It is included in the product package in lib directory.
WEB-INF/lib/itmill-toolkit-themes-4.0.3.jar: This package contains IT Mill Toolkit default themes. It is included in the product package in lib directory.
WEB-INF/itmill-toolkit-license.xml: This is the license for using IT Mill Toolkit. Free development license is included in the product package in lib directory. Deployment licenses can be obtained from www.itmill.com
Your application classes: You must include your application classes either in a JAR file in WEB-INF/lib or as classes in WEB-INF/classes
Your own theme files (OPTIONAL): If your application uses a special theme (look and feel), you must include it in WEB-INF/lib/themes/themename directory.

Deployment descriptor `web.xml`

Deployment descriptor is an XML file with name web.xml in WEB-INF directory. It is a standard component in Java EE that describes how a web application should be deployed. The structure of the deployment descriptor is illustrated by the following example. One simply deploys the applications as servlets implemented by the special com.itmill.toolkit.terminal.web.ApplicationServlet class. The class of the specific application is specified by giving application parameter with the name of the specific application class to the servlet. The servlet is then connected to a URL in a standard way for Java Servlets.

Example 3.1. web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

    <servlet>
        <servlet-name>myservletname</servlet-name>
        <servlet-class>com.itmill.toolkit.terminal.web.ApplicationServlet</servlet-class>
        <init-param>
            <param-name>application</param-name>
            <param-value>MyApplicationClass</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>myapp</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>
</web-app>

For a complete example on how to deploy applications, see demo/itmill-toolkit.war that includes demo applications. You can simply deploy this web application to your favorite application server by server specific means. For example, in Apache Tomcat you simply copy the WAR file to webapps directory.

If you wish to examine the contents of the WAR file, you can decompress it using a standard ZIP or JAR decompressor. For some ZIP implementations, you must rename the file to itmill-toolkit.zip .

Deployment descriptor can have many parameters and options that control the execution of a servlet. You can find a complete documentation of the deployment descriptor in Java Servlet Specification at http://java.sun.com/products/servlet/.

One often needed option is the session timeout. Different servlet containers use varying defaults for timeouts, such as 30 minutes for Apache Tomcat. You can set the timeout with:

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

After the timeout expires, the close() method of the Application class will be called. You should implement it if you wish to handle timeout situations.

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Application Environment