In the snippet you can see a message driven bean set up to consume asynchronously messages from a JMS queue:
import javax.ejb.ActivationConfigProperty;
import javax.ejb.MessageDriven;
import javax.ejb.MessageDrivenContext;
import javax.ejb.TransactionAttribute;
import javax.ejb.TransactionAttributeType;
import javax.inject.Inject;
import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.MessageListener;
import javax.jms.TextMessage;
import javax.xml.bind.JAXBException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
@MessageDriven(
name = "AccountMessageBean",
activationConfig = {
@ActivationConfigProperty(
propertyName = "destinationType",
propertyValue = "javax.jms.Queue"),
@ActivationConfigProperty(
propertyName = "destination",
propertyValue = "java:jboss/exported/queue/account.queue"),
@ActivationConfigProperty(
propertyName = "acknowledgeMode",
propertyValue = "Auto-acknowledge")
})
public class AccountMessageBean implements MessageListener {
private static final Logger logger = LoggerFactory.getLogger(AccountMessageBean.class);
@Inject MessageDrivenContext messageDrivenContext;
@Inject MessageService messageService;
@Override
@TransactionAttribute(TransactionAttributeType.REQUIRED)
public void onMessage(Message message) {
if (!(message instanceof TextMessage)) {
logger.warn("This is not a text message. Break");
return;
}
TextMessage messageText = (TextMessage) message;
try {
if (messageText.getText().contains("organisation")) {
this.messageService.createOrganisation(messageText.getText());
} else if (messageText.getText().contains("person"))
this.messageService.createPerson(messageText.getText());
else {
logger.warn("Something went wrong, must be one of those types");
}
} catch (JMSException | JAXBException e) {
logger.error("An error occured while processing the message, mark to rollback");
messageDrivenContext.setRollbackOnly();
}
}
}
Note the following:
-
@MessageDriven
annotation where the type of the consumed resource is defined (destinationType
- herejavax.jms.Queue
, but it could also bejavax.jms.Topic
), the location of the queue (propertyName = "destination"
) and that the message from the queue is acknowledged once the processing is successful (this is the default setup) - the consuming message driven bean implements the
javax.jms.MessageListener
and the methodonMessage(Message message)
- if a container-managed transaction is not present a new one is created -
@TransactionAttribute(TransactionAttributeType.REQUIRED)
- the consumed message is expected to be text (
javax.jms.TextMessage
) - you access the string value of the message by calling the
getText()
method -messageText.getText()
-
MessageDrivenContext
is used to gain additional access to transaction management - here the transaction is marked for rollback, if an error occursmessageDrivenContext.setRollbackOnly();
(this is only possible in container-based transactions)
Reference -
https://docs.oracle.com/javaee/6/tutorial/doc/bncgl.html#bncgq
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