In the geronimo-web.xml file, application deployer maps the security roles, ejb names, database resources, JMS resources, etc. declared in web.xml to corresponding entities deployed in the server. In addition to that, if there are any web container specific configurations, such as Tomcat or Jetty specific, depending on the application needs, all these settings are configured as well here. If the web application depends on any third party libraries or other services running in the server, all these dependencies are declared in the plan. Some web applications require class loading requirements different from the default class loading behavior. The geronimo-web.xml allows application deployer to configure this as well. There are many more configurations that could be done through geronimo-web.xml depending on the needs of web application. The following sections briefly explain how geronimo-web.xml can be used to configure the web container and web applications.

The geronimo-web.xml uses XML elements from http://geronimo.apache.org/xml/ns/j2ee/web-2.0.1 namespace and one or more namespaces mentioned in Configuring resources in the application scope section earlier in the document.

Sample plan for a Web application

For example, the following web.xml and geronimo-web.xml are the deployment descriptor and Geronimo deployment plan respectively, of a web application that connects to a datasource deployed on DB2 and retrieves data from a table.

<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
         http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">
    
    <resource-ref>
        <res-ref-name>jdbc/DataSource</res-ref-name>
        <res-type>javax.sql.DataSource</res-type>
        <res-auth>Container</res-auth>
        <res-sharing-scope>Shareable</res-sharing-scope>
    </resource-ref>
    
    <welcome-file-list>
        <welcome-file>jsp/EMPdemo.jsp</welcome-file>
    </welcome-file-list>
</web-app>

The web module connects to back end datasource using its JNDI name jdbc/DataSource as declared in the web.xml.

In geronimo-web.xml, a <dependency> element is added to make the the resource archive (RAR) visible to your application, and then a mapping is provided in <resource-ref>.

<web-app xmlns="http://geronimo.apache.org/xml/ns/j2ee/web-2.0.1"
          xmlns:naming="http://geronimo.apache.org/xml/ns/naming-1.2"
          xmlns:sec="http://geronimo.apache.org/xml/ns/security-2.0"
          xmlns:sys="http://geronimo.apache.org/xml/ns/deployment-1.2">

    <sys:environment>
        <sys:moduleId>
            <sys:groupId>samples</sys:groupId>
            <sys:artifactId>EmployeeDemo</sys:artifactId>
            <sys:version>2.5</sys:version>
            <sys:type>war</sys:type>
        </sys:moduleId>
        
        <sys:dependencies>
            <sys:dependency>
                <sys:groupId>samples</sys:groupId>
                <sys:artifactId>EmployeeDatasource</sys:artifactId>
                <sys:version>2.5</sys:version>
                <sys:type>rar</sys:type>
            </sys:dependency>
        </sys:dependencies>
    </sys:environment>
    
    <context-root>/EmployeeDemo</context-root>
        <naming:resource-ref>
        <naming:ref-name>jdbc/DataSource</naming:ref-name>
        <naming:resource-link>jdbc/EmployeeDatasource</naming:resource-link>
    </naming:resource-ref>
</web-app>

Observe the various XML tags and corresponding namespaces used in the deployment plan for various purposes.

<sys:environment> .. </sys:environment> : These elements provide the moduleid configuration and the dependencies. The moduleId elements provide the configuration name for the web module. So, when the web module is deployed, it is given the configuration name samples/EmployeeDemo/2.5/war. The dependencies elements provide the configurations and third party libraries on which the web module is dependent on. These configurations and libraries will be available to the web module via a classloader hierarchy. In this case, the web module is dependent on samples/EmployeeDatasource/2.5/rar which is the configuration of the deployed Datasource that connects to a back end DB2 database. The Datasource deploys a database connection pool (javax.sql.Datasource) with name jdbc/EmployeeDatasource.

<sys:context-root> .. </sys:context-root> : The XML elements used to provide the web context root of the web applications.

<naming:resource-ref> .. </naming:resource-ref> : These elements help us to configure the resource references. In this case, the datasource reference jdbc/DataSource is mapped to jdbc/EmployeeDatasource.

In the EMPdemo.jsp, the following java code snippet is used to obtain a connection from the datasource. It reference the resource from the java:comp/env context entries.

....
....
Context initContext = new InitialContext();
Context envContext  = (Context)initContext.lookup("java:comp/env");
DataSource ds = (DataSource)envContext.lookup("jdbc/DataSource");
Connection con = ds.getConnection();
....
....

The above descriptor and the plan files are the simple illustrations that explain how web modules are developed and assembled for Apache Geronimo. Similarly, many other configurations can be performed in the geronimo-web.xml.

All the XML schema files are located at <geronimo_home>/schema directory. Please go through the .xsd files to have a feel of XML tags that can be used in geronimo-web.xml for configuring web applications.

Container specific configuration in a web application

The container-config element

The <container-config> element is used to hold container specific Web application settings using the following format. None of the Tomcat configuration elements are required, but if specified, they must follow the order in the example below.

<container-config>
    <tomcat xmlns="http://geronimo.apache.org/xml/ns/web/tomcat/config-1.0">
        <!-- Begin Tomcat configuration elements -->
        <host>host</host>
        <cross-context/>
        <disable-cookies/>
        <valve-chain>valve</valve-chain>
        <listener-chain>listener</listener>
        <tomcat-realm>realm</tomcat-realm>
        <manager>manager</manager>
        <cluster>cluster</cluster>
        <!-- End Tomcat configuration elements -->
    </tomcat>
</container-config>

where

• host is the name of a host defined in the name parameter of the initParams attribute of a virtual host <gbean> where the Web application will be deployed. See the Configuring virtual host reference for more information on configuring a virtual host.
• <cross-context/> indicates that this Web application will dispatch requests to other applications and this function should be enabled. Do not specify this tag if you want to disable cross context dispatch requests.
• <disable-cookies/> indicates that this Web application will not use cookies and this function should be disabled. Do not specify this tag if you want to enable cookies.
• valve is the name of a <gbean> that defines the first valve in a valve chain. See the valve chain reference for more information on defining valve chains.
• listener is the name of a <gbean> that defines the first listener in an lifecycle event listener chain. See the lifecycle listener reference for more information on defining lifecycle listener chains.
• realm is the name of a Tomcat realm <gbean> to be used for authentication and authorization for this Web application. If unspecified, the server will use the realm defined in the Tomcat configuration.
• manager is the name of a Tomcat manager <gbean> to be used to manage the Web application resources.
• cluster is the name of a Tomcat cluster <gbean> where the Web application will be deployed. See the Clustering and farming reference for more information on defining a Tomcat cluster.