O'Reilly - Java Message Service

Notification of certain bids on inventory
Java Message Service
A supplier wants notification of requests for bids on specific inventory items at
specific quantities:
String selector =
"InventoryID = 'S93740283-02' AND Quantity BETWEEN 1000 AND 13000";
TopicSubscriber subscriber =
session.createSubscriber(topic, selector,false);
3.4 Message Types
The Java Message Service defines six Message interface types that must be supported by
JMS providers. Although JMS defines the Message interfaces, it doesn't define their
implementation. This allows vendors to implement and transport messages in their own
way, while maintaining a consistent and standard interface for the JMS application
developer. The six message interfaces are Message and its five sub-interfaces: TextMessage,
StreamMessage, MapMessage, ObjectMessage, and BytesMessage.
The Message interfaces are defined according to the kind of payload they are designed to
carry. In some cases, Message types were included in JMS to support legacy payloads that
are common and useful, which is the case with the text, bytes, and stream message types.
In other cases, the Message types were defined to facilitate emerging needs; for example,
ObjectMessage can transport serializable Java objects. Some vendors may provide other
proprietary message types. Progress' SonicMQ and SoftWired's iBus, for example, provide
an XMLMessage type that extends the TextMessage, allowing developers to deal with the
message directly through DOM or SAX interfaces. The XMLMessage type may become a
standard message type in a future version of the specification. At the time of this writing,
Sun Microsystems was starting discussions about adding an XMLMessage type.
3.4.1 Message
The simplest type of message is the javax.jms.Message, which serves as the base interface
to the other message types. As shown below, the Message type can be created and used as a
JMS message with no payload:
// Create and deliver a Message
Message message = session.createMessage( );
publisher.publish(message);
...
// Receive a message on the consumer
public void onMessage(Message message){
// No payload, process event notification
}
This type of message contains only JMS headers and properties, and is used in event
notification. An event notification is a broadcast, warning, or notice of some occurrence. If
the business scenario requires a simple notification without a payload, then the lightweight
Message type is the most efficient way to implement it.
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