Difference between MEL and Groovy?

Question

Why are we using MEL when we have Groovy or why are we using groovy when we have MEL? Both are used for accessing and manipulating the message. Whats make them different

Answer 1

MEL(Mule Expression Language) was originally Mules own expression language it was built on top of MVEL but enriched with additional properties and functions for easily manipulating Mule messages and from the docs has the following benefits:

Use MEL instead of a scripting language such as Groovy, or a programming language such as Java, to manipulate the contents of a message object. Using MEL makes your application more consistent, and provides an efficient and standardized method for evaluating expressions in Mule applications.

MEL is an expression language that provides a consistent, standardized way for developers to work with a Mule message’s payload, properties and variables.

MEL makes use of Mule-specific context objects, you can code it with the help of auto-complete

Great tool for evaluating expressions in your flows

Most importantly, MEL enforces consistency when accessing information in the Mule message: rather than using multiple expression evaluators, you can use MEL, the default expression evaluator, to consistently access and manipulate information.

MEL expressions work within message processors to modify the way the processors act upon the message such as routing or filtering.

However, in Mule 4, MEL has been deprecated in favor of Dataweave, Mules transformation language. Basically they decided whats the point of having two separate languages for transformation and routing etc. So Mule 4 allows you to use Dataweave for routing and more now.

Mule 4 still has support for scripting languages including groovy also.

IMO, it is best practice to use MEL(Mule 3) or Dataweave(Mule 4) for all routing and message manipulation and only really uses scripting languages or Java components for business logic or really complex logic that cannot be accomplished or easily accomplished otherwise.