Chapter 7. Configuring Modules
- Static Modules
- Static Modules are predefined in the
EAP_HOME/modules/directory of the application server. Each sub-directory represents one module and defines a
main/subdirectory that contains a configuration file (
module.xml) and any required JAR files. The name of the module is defined in the
module.xmlfile. All the application server provided APIs are provided as static modules, including the Java EE APIs as well as other APIs such as JBoss Logging.
Example 7.1. Example module.xml file
<?xml version="1.0" encoding="UTF-8"?> <module xmlns="urn:jboss:module:1.0" name="com.mysql"> <resources> <resource-root path="mysql-connector-java-5.1.15.jar"/> </resources> <dependencies> <module name="javax.api"/> <module name="javax.transaction.api"/> </dependencies> </module>The module name,
com.mysql, should match the directory structure for the module, excluding the
main/subdirectory name.The modules provided in JBoss EAP distributions are located in a
systemdirectory within the
EAP_HOME/modulesdirectory. This keeps them separate from any modules provided by third parties.Any Red Hat provided layered products that layer on top of JBoss EAP 6.1 or later will also install their modules within the
systemdirectory.Creating custom static modules can be useful if many applications are deployed on the same server that use the same third-party libraries. Instead of bundling those libraries with each application, a module containing these libraries can be created and installed by the JBoss administrator. The applications can then declare an explicit dependency on the custom static modules.Users must ensure that custom modules are installed into the
EAP_HOME/modulesdirectory, using a one directory per module layout. This ensures that custom versions of modules that already exist in the
systemdirectory are loaded instead of the shipped versions. In this way, user provided modules will take precedence over system modules.If you use the
JBOSS_MODULEPATHenvironment variable to change the locations in which JBoss EAP searches for modules, then the product will look for a
systemsubdirectory structure within one of the locations specified. A
systemstructure must exist somewhere in the locations specified with
- Dynamic Modules
- Dynamic Modules are created and loaded by the application server for each JAR or WAR deployment (or subdeployment in an EAR). The name of a dynamic module is derived from the name of the deployed archive. Because deployments are loaded as modules, they can configure dependencies and be used as dependencies by other deployments.
7.1.2. Global Modules
7.1.3. Module Dependencies
Explicit dependencies are declared by the developer in the configuration file. Static modules can declare dependencies in the
module.xml file. Dynamic modules can have dependencies declared in the
jboss-deployment-structure.xml deployment descriptors of the deployment.
Implicit dependencies are added automatically by the application server when certain conditions or meta-data are found in a deployment. The Java EE 6 APIs supplied with JBoss EAP 6 are examples of modules that are added by detection of implicit dependencies in deployments.
jboss-deployment-structure.xmldeployment descriptor file. This is commonly done when an application bundles a specific version of a library that the application server will attempt to add as an implicit dependency.
Example 7.2. Module dependencies
- Module A declares an explicit dependency on Module C, or
- Module B exports its dependency on Module C.