This topic describes how to work with the message properties to
affect subsequent processing.
There are two different types of message properties:
- System properties (including JMS headers, JMSX properties, and JMS_IBM_properties)
- User properties.
You can work with message properties to affect which messages
a later mediation should process, or to affect processing by a downstream
application or mediation. The rule set in the selector field during mediation
configuration tests values in the message properties.
You can access,
modify and clear properties using the SIMessage interface (see SIMessage.) There are three different sets of methods:
- These properties operate on system properties, plus user properties if
the name is qualified with a prefix user.:
- getMessageProperty
- setMessageProperty
- deleteMessageProperty
- clearMessageProperties
- These properties operate on user properties only, without the need for
the prefix user.:
- getUserProperty
- setUserProperty
- deletUserProperty
- clearUserProperties
- getUserPropertyNames returns a list of the names of the user properties
in the message.
Typically, you can work with message properties in the following way,
when programming a mediation:
- Locate the point in your mediation handler where you insert the
functional mediation code, in the method handle (MessageContext context).
The interface is MessageContext, and you should cast this to SIMessageContext unless you
are only interested in the methods provided by MessageContext.
- Get the SIMessage from the MessageContext object. For example, SIMessage
message = ((SIMessageContext)context).getSIMessage();
- Build your mediation header function in a similar way to these
examples, using the reference information in Message properties support for mediations to help:
- Get a user property of the message. For instance, String
task = (String)msg1.getUserProperty("task");. In this case, the task
string may refer to an operation that the mediation should perform.
- Set a user property, where message Properties are stored as
name-value pairs. The setUserProperty method may only be used to set user
properties, so the name passed into the method should not include the "user."
prefix. For example, msg1.setUserProperty("background","green");
- Delete a user property from the message. For instance, msg1.deleteUserProperty("task");
Mediation function code to work with message properties may look
similar to the code snippet in this example:
String task = (String)msg1.getUserProperty("task");
if (task != null) {
if (task.equals("addColor")) {
msg1.setMessageProperty(SIProperties.JMS_IBM_Format, "colorful");
msg1.setUserProperty("background","green");
msg1.setUserProperty("foreground","purple");
msg1.setUserProperty("depth",new Integer(3));
msg1.deleteUserProperty("task");
}
else {
msg1.clearUserProperties();
}
}