Jms

Front 1

What is JMS?

Back 1

Java Messaging Service is an interface specification that describes an asynchronous messaging system for JEE enterprise applications that facilitates component-to-component communication.

Front 2

Why do we use JMS?

Back 2

An enterprise application provider is likely to choose a messaging API over a tightly coupled API, such as a remote procedure call (RPC), under the following circumstances:

The provider wants the components not to depend on information about other components’ interfaces, so components can be easily replaced.

The provider wants the application to run whether or not all components are up and running simultaneously.

The application business model allows a component to send information to another and to continue to operate without receiving an immediate response.

Front 3

What is synchronous vs. asynchronous messaging in JMS?

Back 3

A JMS client can be set up to synchronously or asynchronously receive messages.

With synchronous delivery, a client can request the next message from a MessageConsumer by using one of three receive methods:

receive - Receive the next message for this consumerreceive (long timeout) - Receive the next message that arrives within the timeout intervalreceiveNoWait - Receive the next message if one is immediately availableWith asynchronous delivery, the client registers an object that implements the MessageListener interface with the JMS server. When messages arrive for a particular MessageConsumer that has a MessageListenered registered, the messages are delivered to the onMessage method.

Front 4

What is new for JMS 2.0?

Back 4

JMS 2.0 includes these improvements over the JMS 1.1 specification:Simplified APIEase of resource configurationMultiple topic users allowed on the same topic subscriptionDelivery delay can now be specified on a message

Front 5

What is a durable subscription?

Back 5

To ensure that a pub/sub application receives all published messages, use PERSISTENT delivery mode for the publishers and durable subscriptions for the subscribers.

Front 6

What are administered objects in JMS?

Back 6

Before the JMS API existed, most messaging products supported either the point-to-point or the publish/subscribe approach to messaging. The JMS specification provides a separate domain for each approach and defines compliance for each domain. A stand-alone JMS provided can implement one or both domains. A Java EE provider must implement both domains.

Front 7

What is the interoperability of JMS with other messaging systems?

Back 7

JMS was originally created to work with IBM’s MQSeries

Front 8

What method is the MessageListener interface?

Back 8

Only one method is there: onMessage() and it is called by the JMS server.

Front 9

Can I send messages to a JBOSS based JMS server from a Weblogic based client?

Back 9

JMS is seamless within a common vendor. However, because JMS specifies interfaces and not implementations connecting clients deployed on products of different vendors requires a “Bridge JMS Server” running a translation application like Camel.

Front 10

What is a topic?

Back 10

In a publish/subscribe (pub/sub) product or application, clients address messages to a topic, which functions somewhat like a bulletin board. Publishers and subscribers are generally anonymous and can dynamically publish or subscribe to the content hierarchy. The system takes care of distributing the messages arriving from a topic’s multiple publishers to its multiple subscribers. Topics retain messages only as long as it takes to distribute them to current subscribers.

Front 11

What is a queue?

Back 11

A point-to-point (PTP) product or application is built on the concept of message queues, senders, and receivers.Each message is address to a specific queue, and receiving clients extract messages from the queues established to hold their messages. Queues retain all messages sent to them until the messages are consumed or expire.