The Connector specification defines the transaction and message inflow system contracts for achieving inbound connectivity from an EIS. The message inflow contract also serves as a standard message provider pluggability contract, thereby allowing various message providers to seamlessly plug in their products with any application server that supports the message inflow contract. In the inbound communication model, the EIS initiates all communication to an application. An application can be composed of enterprise beans (session, entity, or message-driven beans), which reside in an EJB container.
Incoming messages are received through a message endpoint, which is a message-driven bean. This message-driven bean asynchronously consumes messages from a message provider. An application can also synchronously send and receive messages directly using messaging style APIs.
A resource adapter supporting inbound communication provides an instance of an ActivationSpec JavaBean class for each supported message listener type. Each class contains a set of configurable properties that specify endpoint activation configuration information during message-driven bean deployment. The required config-property element in the ra.xml file provides a list of configuration property names required for each activation specification. An endpoint activation fails if the required property values are not specified. Values for the properties that are overridden in the message-driven bean’s deployment descriptor are applied to the ActivationSpec JavaBean when the message-driven bean is deployed.
Administered objects can also be specified for a resource adapter, and these JavaBeans are specific to a messaging style or message provider. For example, some messaging styles may need applications to use special administered objects (such as Queue and Topic objects in JMS). Applications use these objects to send and synchronously receive messages using connection objects using messaging style APIs. For more information about administered objects, see Chapter 18, Using the Java Message Service.