Deploying and Managing Apama Applications > Correlator-Integrated Messaging for JMS > Mapping Apama events and JMS messages > Using expressions in mapping rules
Using expressions in mapping rules
In many cases, a mapping rule requires customization. For example, if you map an event field to a JMS Property, you need to specify which JMS property to use. In other cases you may want to use a constant value in a mapping rule or to create a JUEL expression, for example to execute an XPath query on nested XML documents.
1. Drag a mapping line from the entry in the source tree to the target. If one side of the mapping rule requires a more specific expression, the Connection Participants dialog is displayed.
2. In the Connection Participants dialog's Type field, select an entry from the drop-down list.
3. In the next field enter the name of the JMS Body type, the JMS Property name, a constant value, or a custom JUEL expression. As you enter this information, the expression that wil be used in the mapping rule is displayed in the Expression Value field.
4. Click OK.
For a table of expressions for getting and setting values in JMS messages and recommended mappings to Apama event types, see JUEL Mapping Expressions Reference.
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