Messages are sent using a MessageProducer. For point-to-point this is a QueueSender that is created using the createSender method on QueueSession. A QueueSender is normally created for a specific queue, so that all messages sent using that sender are sent to the same destination. The destination is specified using a Queue object. Queue objects can be either created at runtime, or built and stored in a JNDI namespace.
Queue objects are retrieved from JNDI in the following way:
Queue ioQueue; ioQueue = (Queue)ctx.lookup( qLookup );
WebSphere MQ JMS provides an implementation of Queue in com.ibm.mq.jms.MQQueue. It contains properties that control the details of WebSphere MQ specific behavior, but in many cases it is possible to use the default values. JMS defines a standard way to specify the destination that minimizes the WebSphere MQ specific code in the application. This mechanism uses the QueueSession.createQueue method, which takes a string parameter describing the destination. The string itself is still in a vendor-specific format, but this is a more flexible approach than directly referencing the vendor classes.
WebSphere MQ JMS accepts two forms for the string parameter of createQueue().
public static final String QUEUE = "SYSTEM.DEFAULT.LOCAL.QUEUE" ; . . . ioQueue = session.createQueue( QUEUE );
The URI for a queue begins with the sequence queue://, followed by the name of the queue manager on which the queue resides. This is followed by a further "/", the name of the queue, and optionally, a list of name-value pairs that set the remaining Queue properties. For example, the URI equivalent of the previous example is:
ioQueue = session.createQueue("queue:///SYSTEM.DEFAULT.LOCAL.QUEUE");
Note that the name of the queue manager is omitted. This is interpreted as the queue manager to which the owning QueueConnection is connected at the time when the Queue object is used.
The following example connects to queue Q1 on queue manager HOST1.QM1, and causes all messages to be sent as non-persistent and priority 5:
ioQueue = session.createQueue("queue://HOST1.QM1/Q1?persistence=1&priority=5");
Table 15 lists the names that can be used in the name-value part of
the URI. A disadvantage of this format is that it does not support
symbolic names for the values, so where appropriate, the table also indicates
'special' values. Note that these special values may be
subject to change. (See Setting properties with the 'set' method for an alternative method to set properties.)
Table 15. Property names for queue URIs
| Property | Description | Values |
|---|---|---|
| expiry | Lifetime of the message in milliseconds | 0 for unlimited, positive integers for timeout (ms) |
| priority | Priority of the message | 0 through 9, -1=QDEF, -2=APP |
| persistence | Whether the message should be 'hardened' to disk | 1=non-persistent, 2=persistent, -1=QDEF, -2=APP |
| CCSID | Character set of the destination | integers - valid values listed in base WebSphere MQ documentation |
| targetClient | Whether the receiving application is JMS compliant or not | 0=JMS, 1=MQ |
| encoding | How to represent numeric fields | An integer value as described in the base WebSphere MQ documentation |
| ||
Once the Queue object is obtained (either using createQueue as above or from JNDI), it must be passed into the createSender method to create a QueueSender:
QueueSender queueSender = session.createSender(ioQueue);
The resulting queueSender object is used to send messages by using the send method:
queueSender.send(outMessage);
You can set Queue properties by first creating an instance of com.ibm.mq.jms.MQQueue using the default constructor. Then you can fill in the required values by using public set methods. This method means that you can use symbolic names for the property values. However, because these values are vendor-specific, and are embedded in the code, the applications become less portable.
The following code fragment shows the setting of a queue property with a set method.
com.ibm.mq.jms.MQQueue q1 = new com.ibm.mq.jms.MQQueue();
q1.setBaseQueueManagerName("HOST1.QM1");
q1.setBaseQueueName("Q1");
q1.setPersistence(DeliveryMode.NON_PERSISTENT);
q1.setPriority(5);
Table 16 shows the symbolic property values that are supplied with
WebSphere MQ JMS for use with the set methods.
Table 16. Symbolic values for queue properties
| Property | Admin tool keyword | Values |
|---|---|---|
| expiry |
UNLIM APP |
JMSC.MQJMS_EXP_UNLIMITED JMSC.MQJMS_EXP_APP |
| priority |
APP QDEF |
JMSC.MQJMS_PRI_APP JMSC.MQJMS_PRI_QDEF |
| persistence |
APP QDEF PERS NON |
JMSC.MQJMS_PER_APP JMSC.MQJMS_PER_QDEF JMSC.MQJMS_PER_PER JMSC.MQJMS_PER_NON |
| targetClient |
JMS MQ |
JMSC.MQJMS_CLIENT_JMS_COMPLIANT JMSC.MQJMS_CLIENT_NONJMS_MQ |
| encoding |
Integer(N) Integer(R) Decimal(N) Decimal(R) Float(N) Float(R) Native |
JMSC.MQJMS_ENCODING_INTEGER_NORMAL JMSC.MQJMS_ENCODING_INTEGER_REVERSED JMSC.MQJMS_ENCODING_DECIMAL_NORMAL JMSC.MQJMS_ENCODING_DECIMAL_REVERSED JMSC.MQJMS_ENCODING_FLOAT_IEEE_NORMAL JMSC.MQJMS_ENCODING_FLOAT_IEEE_REVERSED JMSC.MQJMS_ENCODING_NATIVE |
See The ENCODING property for a discussion on encoding.
JMS provides several message types, each of which embodies some knowledge of its content. To avoid referencing the vendor-specific class names for the message types, methods are provided on the Session object for message creation.
In the sample program, a text message is created in the following manner:
System.out.println( "Creating a TextMessage" );
TextMessage outMessage = session.createTextMessage();
System.out.println("Adding Text");
outMessage.setText(outString);
The message types that can be used are:
Details of these types are in Chapter 14, JMS interfaces and classes.