Why message driven bean

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In order to achieve message ordering, it is necessary to limit the session pool for the MDB to 1. The delivery active configuration of the message-driven beans MDB indicates whether the MDB is receiving messages or not. If an MDB is not receiving messages, then the messages will be saved in the queue or topic according to the topic or queue rules.

You can configure the active attribute of the delivery-group using XML or annotations, and you can change its value after deployment using the management CLI.

By default, the active attribute is activated and delivery of messages occurs as soon as the MDB is deployed. In the jboss-ejb3. You can also use the org.

DeliveryActive annotation. For example:. If you use Maven to build your project, make sure you add the following dependency to the pom. You can configure the active attribute of the delivery-group after deployment using the management CLI. These management operations dynamically change the value of the active attribute, enabling or disabling delivery for the MDB.

This method of changing the delivery active value does not persist if you restart the server. At runtime, connect to the instance you want to manage, then enter the path of the MDB for which you want to manage the delivery.

You see the status as Delivery Active: true or Delivery Active: false. Delivery groups provide a way to manage the delivery-active state for a group of MDBs. Every MDB belonging to a delivery group has delivery active if and only if that group is active, and has delivery inactive whenever the group is not active.

On the server side, delivery-groups can be enabled by having their active attribute set to true , or disabled by having their active attribute set to false , as shown in the example below:. The state of delivery-groups can be updated using the management CLI. When you set the delivery active in the jboss-ejb3. However, when you use the management CLI to stop or start the delivery, it does not persist on server restart.

You can use the org. DeliveryGroup annotation on each MDB class belonging to a group:. When an MDB is identified as a clustered singleton and is deployed in a cluster, only one node is active. This node can consume messages serially. When the server node fails, the active node from the clustered singleton MDBs starts consuming the messages. You have to activate the delivery-group in the entire cluster, specifically, in all nodes of the cluster, because you do not know which node of the cluster is chosen to be the singleton master.

If the server chooses a node to be singleton master , and that node does not have the required delivery-group activated, no node in the cluster receives the messages. It uses the same source code as the helloworld-mdb quickstart, with a difference only in the configuration to run it as a clustered singleton.

There are two JMS resources contained in this quickstart:. Both contain a singleton configuration as specified in the jboss-ejb3. As a result, only one node in the cluster will have those MDBs active at a specific time. If this active node shuts down, another node in the cluster will become the active node with the MDBs, which then becomes the singleton provider. You can also find a configuration for the delivery group in the jboss-ejb3.

All the delivery groups used by an MDB must be configured in the ejb3 subsystem configuration. The delivery group can be enabled or disabled.

If the delivery group is disabled in a cluster node, all the MDBs belonging to that delivery group become inactive in the respective cluster node.

When using the delivery groups in a non-clustered environment, the MDB is active whenever the delivery group is enabled. If a delivery group is used in conjunction with the singleton provider, the MDB can be active in the singleton provider node only if that node has the delivery group enabled.

Otherwise, the MDB will be inactive in that node, and all the other nodes of the cluster. This procedure creates an EJB 3. Open the Create EJB 3. There are three sets of details to specify for the bean class here: project, Java class, and message destination. Message Destination:. These are the details you must supply for a JMS-based message-driven bean:.

Set Destination type to Queue or Topic as required. Click the Next button. The default values here are suitable for a JMS-based message-driven bean using container-managed transactions.

Click the Finish button. The message-driven bean is created with stub methods for the default constructor and the onMessage method. To specify a resource adapter in jboss-ejb3. They are not created on all nodes in a cluster unless the MDB is also deployed to all nodes in the cluster.

Because objects configured by these annotations are only created on the server where the MDB is deployed, this affects remote JCA topologies where an MDB reads messages from a remote server and then sends them to a remote server.