Java Message Service, 2nd Edition

Examining a Queue

A QueueBrowser is a specialized object that allows you to peek ahead at pending messages on a Queue without actually consuming them. This feature is unique to point-to-point messaging. Queue browsing can be useful for monitoring the contents of a queue from an administration tool or for browsing through multiple messages to locate a message that is more important than the one at the head of the queue. It is also useful for other monitoring tasks, such as determining the current queue depth.

Messages obtained from a QueueBrowser are copies of messages contained in the queue and are not considered to be consumed—they are merely for browsing. It is also important to note that the QueueBrowser is not guaranteed to have a definitive list of messages in the queue. The QueueBrowser contains only a snapshot, or a copy of, the queue as it appears at the time the QueueBrowser is created. The contents of the queue may change between the time the browser is created and the time you examine its contents. However, no matter how small that window of time is, new messages may arrive and other messages may be consumed by other JMS clients.

A QueueBrowser is created from the Session object using the createBrowser() method. This method takes as an argument the queue from which you would like to view the messages. It is during the createBrowser() method invocation that the snapshot is taken from the queue. You can then get a list of the messages by using the method getEnumeration() ...