Appendix A. Mule Expression Language

The Mule Expression Language (MEL) is based on the MVFLEX Expression Language (MVEL; see, a hybrid dynamic/statically typed language. We strongly recommend you get acquainted with MVEL by reading its online documentation ( MEL itself is also extensively documented online ( This appendix is a quick reference guide to Mule-specific features of MEL. It also provides a quick overview on how to customize MEL to implement custom needs.

A.1. MEL quick reference

Mule binds custom objects, variables, and functions within the MEL context to facilitate accessing Mule resources, processing messages, and so on.

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