Message-driven beans - JCA components
This topic provides an overview of the administrative components that you configure for message-driven beans as listeners on a Java Connector Architecture (JCA) 1.5 resource adapter.
Components for a JCA resource adapter
To handle non-JMS requests inbound to WAS from enterprise information systems, message-driven beans use a Java Connector Architecture (JCA) 1.5 resource adapter written by a third party for that purpose.
With a Java Connector Architecture (JCA) 1.5 resource adapter, a message-driven bean acts as a listener on a specific endpoint. In the JCA 1.5 specification, such message-driven beans are commonly called message endpoints or simply endpoints.
Each application configuring one or more message-driven beans must specify the resource adapter that sends messages to the endpoint. To specify the resource adapter, you configure the message-driven bean to use an activation specification that has been configured by the administrator for the resource adapter. Figure 1. Message-driven bean components for a JCA resource adapter. This figure shows the main components of WebSphere support for message-driven beans for use with an external JCA resource adapter.
The administrator creates a J2C activation specification for the appropriate resource adapter to provide information to the deployer about the configuration properties of an endpoint instance (message-driven bean) related to the processing of the inbound messages. Properties specified on an activation specification can be overridden by appropriately named activation-configuration properties in the deployment descriptor of an associated EJB 2.1 message-driven bean.
When a deployed message-driven bean is installed, it is associated with an activation specification for an endpoint. When a message arrives on the endpoint, the message is passed to a new instance of a message-driven bean for processing.
Administered object definitions and classes are provided by a resource adapter when you install it. Using this information, the administrator can create and configure J2C administered objects with JNDI names that are then available for applications to use. Some messaging styles may need applications to use special administered objects for sending and synchronously receiving messages (through connection objects using programming interfaces specific to a messaging style). Administered objects can also be used to perform transformations on an asynchronously-received message in a way that is specific to a message provider. Administered objects can be accessed by a component by using either a message destination reference (preferred) or a resource environment reference.
JMS components used with a JCA messaging provider
Message-driven beans that implement the javax.jms.MessageListener interface can be used for JMS messaging. For JMS messaging, message-driven beans can use a JCA-based messaging provider such as the SIB JMS Resource Adapter (which is the default messaging provider listed under JMS providers) that is part of WebSphere Application Server and configure message-driven beans to use a JCA activation specification. Figure 2. Message-driven bean components for the default messaging provider. This figure shows the main components of WebSphere support for message-driven beans for use with the default messaging provider.
With the SIB JMS Resource Adapter, a message-driven bean acts as a listener on a specific JMS destination.
The administrator creates a JMS activation specification (which, the WebSphere console shows on the panel Resources > JMS providers > Default messaging > JMS activation specifications) to provide information to the deployer about the configuration properties of a message-driven bean related to the processing of the inbound messages. WebSphere provides additional support for JCA activation specifications that are JMS-based and shows the JMS-specific panel rather than the generic JCA activation specification panel. For example, a JMS activation specification specifies the name of the service integration bus to connect to, and includes information about the message acknowledgement modes, message selectors, destination types, and whether or not durable subscriptions are shared across connections with members of a server cluster. Properties specified on an activation specification can be overridden by appropriately named activation-configuration properties in the deployment descriptor of an associated EJB 2.1 message-driven bean.
The administrator also creates other administered objects that configure the JMS destination and the associated resources of a service integration bus that are used to implement messaging with that JMS destination. For more information about JMS resources and service integration, see Learning about the default messaging provider.
Related concepts
JMS components on V5 nodes
Message-driven beans - automatic message retrieval