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The <sys:environment> XML element uses the Geronimo System namespace, which is used to specify the common elements for common libraries and module-scoped services, and is described at here:

• http://geronimo.apache.org/schemas-2.1/docs/geronimo-module-1.2.xsd.html^{Image Added}

. The <sys:environment> element contains the following elements:

• The <moduleId> element is used to provide the configuration name for the EJB JAR application as deployed in the Geronimo server. It contains elements for the groupId, artifactId, version and module type. Module IDs are normally printed with slashes between the four components, such as GroupID/ArtifactID/Version/Type.
  
  
• The <dependencies> element is used to provide the configurations and third party libraries on which the EJB module is dependent upon. These configurations and libraries are made available to the EJB module via the Geronimo classloader hierarchy.
  
  
• The <hidden-classes> element can be used to provide some degree of control of the Geronimo classloader hierarchy, and mitigate clashes between classes loaded by the server and classes loaded by the EJB module. It is used to lists packages or classes that may be in a parent classloader, but must not be exposed to the web application. Since Geronimo is entirely open-source and utilizes many other open-source libraries it is possible that the server itself and the web application may have different requirements and/or priorities for the same open source project libraries. The <hidden-classes> element is typically used when the EJB application has requirements for a specific version of a library that is different than the version used by Geronimo itself. A simple example of this is when an EJB module uses, and most importantly includes, a version of the Log4J common logging library that is different than the version used by the Geronimo server itself. This might not provide the desired results. Thus, the <hidden-classes> element can be used to "hide" the Log4J classes loaded by all the parent classloaders of the EJB module, including those loaded by and for the Geronimo server itself, and only the Log4J classes included with the EJB module library will get loaded.
  
  
• The <non-overridable-classes> element can also be used to provide some degree of control of the Geronimo classloader hierarchy, but in the exact opposite manner than provided by the <hidden-classes> element. This element can be used to specify a list of classes or packages which will only be loaded from the parent classloader of the EJB module to ensure that the Geronimo server's version of a libary is used instead of the version included with the web application.
  
  
• The <inverse-classloading> element can be used to specify that standard classloader delegation is to be reversed for this module. The Geronimo classloader delegation follows the Java EE 5 specifications, and the normal behavior is to load classes from a parent classloader (if available) before checking the current classloader. When the <inverse-classloading> element is used, this behavior is reversed and the current classloader will always be checked before looking in the parent classloader(s). This element is similar to the <hidden-classes> element since the desired behavior is to give the libraries packaged with the EJB JAR application (i.e., in META-INF/lib) precedence over anything used by the Geroimo server itself specify a list of classes which will never be loaded from parent ClassLoaders of this module. For example, if Log4J was listed here, the module would never see Geronimo's copy of Log4J. If the module provided it's own Log4J JAR it would use that, otherwise it would not be able to load Log4J at all.
  The <non-overridable-classes> element can be used to specify a list of classes which will only be loaded from parent ClassLoaders of this module (never from the module's own ClassLoader). For example, this is used to prevent a EJB application from redefining "javax.servlet", so those classes will always be loaded from the server instead of from the EJB application's own ClassPath.
  The <inverse-classloading> element can be used to specify that standard classloader delegation is to be reversed for this module.
  
  
• The <suppress-default-environment> element can be used to suppress inheritance of environment by module (i.e., any default environment built by a Geronimo builder when deploying the plan will be suppressed). If the <suppress-default-environment> element is specified then any default environment build by a Geronimo builder when deploying the plan will be suppressed. An example of where this is useful is when deploying a connector on an app client in a separate (standalone) module (not as part of a client plan). The connector builder defaultEnvironment includes some server modules that won't work on an app client, so you need to suppress the default environment and supply a complete environment including all parents for a non-app-client module you want to run on an app client. This element should not be used for EJB applications however.

An example openejb-jar.xml file is shown below using the <sys:environment> element:

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