Java Platform, Enterprise Edition (Java EE) 8 The Java EE Tutorial

## Metadata Annotations

Java EE Connector Architecture provides a set of annotations to minimize the need for deployment descriptors.

- The `@Connector` annotation can be used by the resource adapter developer to specify that the JavaBeans component is a resource adapter JavaBeans component. This annotation is used for providing metadata about the capabilities of the resource adapter. Optionally, you can provide a JavaBeans component implementing the `ResourceAdapter` interface, as in the following example:

      @Connector(
          displayName = "TrafficResourceAdapter",
          vendorName = "Java EE Tutorial",
          version = "7.0"
      )
      public class TrafficResourceAdapter implements ResourceAdapter,
                                                     Serializable {
          ...
      }

- The `@ConnectionDefinition` annotation defines a set of connection interfaces and classes pertaining to a particular connection type, as in the following example:

      @ConnectionDefinition(
          connectionFactory = ConnectionFactory.class,
          connectionFactoryImpl = TradeConnectionFactory.class,
          connection = Connection.class,
          connectionImpl = TradeConnection.class
      )
      public class TradeManagedConnectionFactory ... {
          ...
      }

- The `@AdministeredObject` annotation designates a JavaBeans component as an administered object.

- The `@Activation` annotation contains configuration information pertaining to inbound connectivity from an EIS instance, as in the following example:

      @Activation(
              messageListeners = { TrafficListener.class }
      )
      public class TrafficActivationSpec implements ActivationSpec,
                                                    Serializable {
          ...
          @ConfigProperty()
          /* port to listen to requests from the EIS */
          private String port;
          ...
      }

- The `@ConfigProperty` annotation can be used on JavaBeans components to provide additional configuration information that may be used by the deployer and resource adapter provider. The preceding example code shows several `@ConfigProperty` annotations.

- The `@ConnectionFactoryDefinition` annotation is a resource definition annotation that is used to define a connector connection factory and register it in JNDI under the name specified in the mandatory `name` annotation element. The mandatory `interfaceName` annotation element specifies the fully qualified name of the connection factory interface class. The `transactionSupport` annotation element specifies the level of transaction support the connection factory needs to support. The `minPoolSize` and `maxPoolSize` annotation elements specify the minimum or maximum number of connections that should be allocated for a connection pool that backs this connection factory resource. Additional properties associated with the connection factory being defined can be specified through the `properties` element.

  Since repeated annotations are not allowed, the `@ConnectionFactoryDefinitions` annotation acts as a container for multiple connector connection factory definitions. The `value` annotation element contains the multiple connector connection factory definitions.

- The `@AdministeredObjectDefinition` annotation is a resource definition annotation that is used to define an administered object and register it in JNDI under the name specified in the mandatory `name` annotation element. The mandatory fully qualified name of the administered object’s class must be indicated by the `className` element. Additional properties that must be configured in the administered object can be specified through the `properties` element.

  Since repeated annotations are not allowed, the `@AdministeredObjectDefinitions` annotation acts as a container for multiple administered object definitions. The `value` annotation element contains the multiple administered object definitions.

The specification allows a resource adapter to be developed in mixed-mode form, that is the ability for a resource adapter developer to use both metadata annotations and deployment descriptors in applications. An application assembler or deployer may use the deployment descriptor to override the metadata annotations specified by the resource adapter developer.

The deployment descriptor for a resource adapter, if present, is named `ra.xml`. The `metadata-complete` attribute defines whether the deployment descriptor for the resource adapter module is complete or whether the class files available to the module and packaged with the resource adapter need to be examined for annotations that specify deployment information.

For the complete list of annotations and JavaBeans components provided in the Java EE platform, see the Java EE Connector Architecture 1.7 specification.

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