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3.7. Class Loading and Subdeployments

3.7.1. Modules and Class Loading in Enterprise Archives

Enterprise Archives (EAR) are not loaded as a single module like JAR or WAR deployments. They are loaded as multiple unique modules.
The following rules determine what modules exist in an EAR.
  • The contents of the lib/ directory in the root of the EAR archive is a module. This is called the parent module.
  • Each WAR and EJB JAR subdeployment is a module. These modules have the same behavior as any other module as well as implicit dependencies on the parent module.
  • Subdeployments have implicit dependencies on the parent module and any other non-WAR subdeployments.
The implicit dependencies on non-WAR subdeployments occur because JBoss EAP 6 has subdeployment class loader isolation disabled by default. Dependencies on the parent module persist, regardless of subdeployment class loader isolation.

Important

No subdeployment ever gains an implicit dependency on a WAR subdeployment. Any subdeployment can be configured with explicit dependencies on another subdeployment as would be done for any other module.
Subdeployment class loader isolation can be enabled if strict compatibility is required. This can be enabled for a single EAR deployment or for all EAR deployments. The Java EE 6 specification recommends that portable applications should not rely on subdeployments being able to access each other unless dependencies are explicitly declared as Class-Path entries in the MANIFEST.MF file of each subdeployment.
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3.7.2. Subdeployment Class Loader Isolation

Each subdeployment in an Enterprise Archive (EAR) is a dynamic module with its own class loader. By default a subdeployment can access the resources of other subdeployments.
If a subdeployment is not to be allowed to access the resources of other subdeployments, strict subdeployment isolation can be enabled.
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3.7.3. Enable Subdeployment Class Loader Isolation Within a EAR

This task shows you how to enable subdeployment class loader isolation in an EAR deployment by using a special deployment descriptor in the EAR. This does not require any changes to be made to the application server and does not affect any other deployments.

Important

Even when subdeployment class loader isolation is disabled it is not possible to add a WAR deployment as a dependency.

  1. Add the deployment descriptor file

    Add the jboss-deployment-structure.xml deployment descriptor file to the META-INF directory of the EAR if it doesn't already exist and add the following content: 
    <jboss-deployment-structure>

</jboss-deployment-structure>

  2. Add the <ear-subdeployments-isolated> element

    Add the <ear-subdeployments-isolated> element to the jboss-deployment-structure.xml file if it doesn't already exist with the content of true. 
    <ear-subdeployments-isolated>true</ear-subdeployments-isolated>
Result:

Subdeployment class loader isolation will now be enabled for this EAR deployment. This means that the subdeployments of the EAR will not have automatic dependencies on each of the non-WAR subdeployments.

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