JMS Messages  

JMS messages are lightweight components that the applications exchange. The messages consist of three parts:

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●      Header – used to identify and route the JMS message. The header of a message consists of the following fields:

○       JMSDestination – the description of the destination the message is sent to.

○       JMSDeliveryMode – defines the delivery mode specified for the message when it is sent.

○       JMSMessageID – the unique value specified for the message when it is sent.

○       JMSTimestamp – the time required by the provider to send the message to a destination.

○       JMSCorrelationID – shows whether the message is linked to another message.

○       JMSReplyTo – the destination the message reply should be sent to.

○       JMSRedelivered – if this field is set to true, this means that the message may have been redelivered in the past. That means that the application has to take extra precautions to prevent duplicate processing.

○       JMSType – the message type identifier.

○       JMSExpiration – contains the value that shows the expiration period of the message.

○       JMSPriority – shows the priority of the message.

·        Properties – used optionally to define application specific key-value pairs.

·        Body – the message data.

Messages Types

There are a few message types that the applications can create and receive. Each type of message body can contain a specific type of data and is unpacked in a different way.

·        Bytes Messages – this type of messages represents a stream of uninterpreted bytes. You can use this message type to encode a message body to match another existing message format.

·        Map Messages – the message has a message body created by a set of name-value pairs. In this pair, the names are of the Java language string type. The values are Java language primitive types. These entries can be accessed in random order by name or by enumeration. There is no order of the entries.

·        Object Messages – the messages represent a messages body that is a Serializable object.

·        Stream Messages – the stream message contains a stream of Java language primitive values. This message data is read in sequences.

·        Text Messages – a message that contains java.lang.Stringdata.

For more information about using the messages that are received, see Processing the Received Messages. For more information about message acknowledgement, see Message Acknowledgement.