Appendix A. The expression evaluation framework
Mule offers a rich expression evaluation framework that allows you to hook advanced logic into different parts of your configuration. In chapters 4 and 5, we mentioned the possibility of using evaluators. In this appendix, we’ll review the existing evaluators and present different examples, side by side, to help you realize how versatile and powerful they are.
In short, an expression evaluator evaluates an expression on an object. The nature of the expression and the type of object accepted actually depends on the type of the evaluator. Most of the time, the object consists of the instance of MuleMessage that’s currently under processing.
Table A.1 presents an overview of the evaluators available in Mule at the time of this writing.[1] Note how each evaluator has an ID: this is the ID that you’ll need to use in your configuration to tell Mule what evaluator to use.
1 Refer to the JavaDoc of your installed Mule for the most accurate evaluators list and description.