JMS headers and properties

A JMS message consists of headers, properties and the body. Headers are accessed differently than properties and were not available in previous versions. In this version you can specify how to deal with headers and properties.

JMS headers

JMS headers are predefined named values that are present in all messages (although the value might be null). The following is a list of JMS header names this Connector supports:

JMSCorrelationID

(String) This header is set by the application for use by other applications.

JMSDeliveryMode

(Integer) This header is set by the JMS provider and denotes the delivery mode.

JMSExpires

(Long) A value of zero means that the message does not expire. Any other value denotes the expiration time for when the message is removed from the queue.

JMSMessageID

(String) The unique message ID. Note that this is not a required field and can be null.

Since the JMS provider might not use your provided message ID, the Connector sets a special property called $jms.messageid after sending a message. This is to insure that the message ID always is available to the user. To retrieve this value use conn.getProperty("$jms.messageid") in your After Add hook.

JMSPriority

(Integer) The priority of the message.

JMSTimestamp

(Long) The time the message was sent.

JMSType

(String) The type of message.

JMSReplyTo

(Destination) The queue/topic the sender expects replies to. When receiving a message this value holds the provider specific Destination interface object and is typically an internal Queue or Topic object. When sending a message you must either reuse the incoming Destination object or set the value to a valid topic/queue name. If the value is NULL (for example, an attribute with no values) or the string "%this%" the Connector uses its own queue/topic as the value. The difference between this method and explicitly setting the queue/topic name is that you need not update the attribute assignment if you change your Connector configuration's queue/topic name.

There is one restriction in the current version which enables you to only request a reply to the same type of connection as you are currently connected to. This means that you cannot publish a message on a topic and request the reply to a queue and vice versa.

It is not mandatory to respond to this header so the receiver of the message can completely ignore this field without any form of punishment.

These headers are all set by the provider and might be acted upon by the JMS driver for outgoing messages. In the configuration screen you can specify that you want all headers returned as attributes or specify a list of those of interest. All headers are named using a prefix of jms.. Also note that JMS header names always start with the string JMS. This means that you must never use property names starting with jms.JMS as they can be interpreted as headers.

Depending on the operation mode, the JMS Connector sets the following additional properties to its conn Entry.

messageType

This property holds the type of message that was read or the message that is to be written. Its value overwrites the Select Message Type configuration parameter. For example:

var messgeType = conn.getProperty("$jms.messageType ");

message

This property holds the message that was read. The original message can be accessed from the After GetNext (Iterator mode), After Lookup (Lookup mode), or After CallReply (CallReply mode) hooks.

messageid

This property holds the ID of the message that has been written. This ID can be accessed from the After Add hook in AddOnly mode.

JMS Properties

In previous versions of this Connector all JMS properties were copied between the Entry object and the JMS Message. In this release you can refine this behavior by telling the Connector to return all user defined properties as attributes or specify a list of properties of interest. All properties are prefixed with jms. to separate them from other attributes. If you leave the list of properties blank and clear the JMS Properties As Attributes flag, you get the same behavior as for previous versions. Both JMS headers and JMS properties can be set by the user. If you use the backwards compatible mode you must set the entry properties in the Before Add hook as in:

conn.setProperty ( "jms.MyProperty", "Some Value" );

If you either check the JMS Properties As Attributes flag or specify a list of properties, you must provide the JMS properties as attributes. One way to do that is to add attributes using the jms. prefix in your attribute map. For example, if you add jms.MyProperty attribute map it results in a JMS property named MyProperty.