If you follow Java EE, the simplified API components in JMS 2.0 (Java EE 7) will not be unknown to you. One of the important interfaces which forms a part of the simplified API is the javax.jms.JMSContext interface.
JMSContext can be categorized in to two types depending on how it’s instance is obtained and managed (life cycle) – Container managed and Application managed
Application Managed
Let’s look at a code snippet:
@Path("email")
@Stateless
public class EmailService {
//pulls in default Conn Factory as per Java EE 7
@Resource
ConnectionFactory cf;
//application managed
JMSContext ctx;
@Resource("jms/emailQ")
Destination emailQ;
@POST
public void send(String email) {
Session session;
try {
ctx = cf.createContext();
ctx.createProducer().send(emailQ, email);
System.out.println("Message Sent to queue - " + ((Queue) emailQ).getQueueName());
} catch (JMSException ex) {
Logger.getLogger(EmailService.class.getName()).log(Level.SEVERE, null, ex);
throw new JMSRuntimeException(ex.getMessage(), ex.getMessage(), ex);
} finally {
//clean up after use. Can also be done as inside a @PreDestroy callback method
ctx.close();
System.out.println("JMSContext closed");
}
}
}
In this case, an instance of JMSContext was obtained using ConnectionFactory and hence needs to be closed by the application code. The container will not manage it’s lifecycle
Container Managed
If you use @Inject to allow the container to inject the JMSContext instance, the container assumes full responsibility for it’s lifecycle.
@Path("email")
@Stateless
public class AwesomeEmailService {
//container managed
@Inject
JMSContext ctx;
@Resource("jms/emailQ")
Destination emailQ;
@POST
public void send(String email) {
Session session;
try {
ctx.createProducer().send(emailQ, email);
System.out.println("Message Sent to queue - " + ((Queue) emailQ).getQueueName());
} catch (JMSException ex) {
Logger.getLogger(AwesomeEmailService.class.getName()).log(Level.SEVERE, null, ex);
throw new JMSRuntimeException(ex.getMessage(), ex.getMessage(), ex);
}
}
}
If you call close() on a container managed JMSContext, you will end up with this exception – javax.jms.IllegalStateRuntimeException: This method is not permitted on a container-managed (injected) JMSContext.
And….
In the previous example, the container automatically uses the default Connection Factory (as per Java EE 7). You can also leverage @JMSConnectionFactory annotation (another useful addition to JMS 2.0) to specify a Connection Factory of your choice.
@Path("email")
@Stateless
public class TheBestEmailService {
//container managed
@Inject
@JMSConnectionFactory("jms/myConnectionFactory")
JMSContext ctx;
@Resource("jms/emailQ")
Destination emailQ;
@POST
public void send(String email) {
Session session;
try {
ctx.createProducer().send(emailQ, email);
System.out.println("Message Sent to queue - " + ((Queue) emailQ).getQueueName());
} catch (JMSException ex) {
Logger.getLogger(TheBestEmailService.class.getName()).log(Level.SEVERE, null, ex);
throw new JMSRuntimeException(ex.getMessage(), ex.getMessage(), ex);
}
}
}
That’s it for now.. Cheers !
| Reference: | Types of JMSContext in JMS 2.0 from our JCG partner Abhishek Gupta at the Object Oriented.. blog. |
