O'Reilly - Java Message Service

3.1.1.3 JMSMessageID
Java Message Service
The JMSMessageID is a String value that uniquely identifies a message. How unique the
identifier is depends on the vendor. The JMSMessageID can be useful for historical
repositories in JMS consumer applications where messages need to be uniquely indexed.
Used in conjunction with the JMSCorrelationID, the JMSMessageID is also useful for
correlating messages:
String messageid = message.getJMSMessageID( );
3.1.1.4 JMSTimestamp
The JMSTimestamp is set automatically by the message producer when the send( )
operation is invoked. The timestamp is a long value that measures time in milliseconds:
long timestamp = message.getJMSTimestamp( );
3.1.1.5 JMSExpiration
A Message object's expiration date prevents the message from being delivered to
consumers after it has expired. This is useful for messages whose data is only valid for a
period of time:
long timeToLive = message.getJMSExpiration( );
The expiration time for messages is set in milliseconds on the producer (i.e.,
TopicPublisher) using the setTimeToLive( ) method:
TopicPublisher topicPublisher = topicSession.createPublisher(topic);
// Set time to live as 1 hour (1000 millis x 60 sec x 60 min)
topicPublisher.setTimeToLive(3600000);
By default the timeToLive is zero (0), which indicates that the message doesn't expire.
Calling setTimeToLive( ) with a zero argument ensures that a message is created without
an expiration date.
3.1.1.6 JMSRedelivered
The JMSRedelivered header indicates that the message was redelivered to the consumer.
The JMSRedelivered header is true if the message is redelivered, and false if it's not. A
message may be marked redelivered if a consumer failed to acknowledge previous delivery
of the message, or when the JMS provider is not certain whether the consumer has already
received the message:
boolean isRedelivered = message.getJMSRedelivered( )
Message redelivery is covered in more detail in Chapter 6.
3.1.1.7 JMSPriority
The message producer may assign a priority to a message when it is delivered. There are
two categories of message priorities: levels 0-4 are gradations of normal priority; levels 5-
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