This presentation provides you an introduction to Mule Expression Language. You can watch the demo through the following link : https://youtu.be/fAj98tFqv_M

1. Karthik Selvaraj

2. Introduction
 Mule Expression Language (MEL) was introduced in
Mule 3.3.0
 Prior to version 3.3.0, expressions in Mule varied in
syntax according to their specific evaluator.
 The variation in syntax rules was time-consuming to
learn and hence MEL was created to address this
complexity.
 Mule Expression Language (MEL), implements a
single set of syntax rules.

3. Expression VS Scripting language
 An expression language, such as MEL, is similar, but
not the same as, a scripting language. It allows you to
write short scripts that resolve dynamically to get
values, set values, or perform an operation on data.
 Scripting languages are generally more useful if you
are writing something complex enough to require
more than just a few lines of code, or if you need to
include conditional logic.
 If you need to get or set values, invoke methods, or
perform functions, you can do so quickly and easily
using an expression language.

4. MEL – Assigning Values
 Point the cursor to value field and press CTRL + Space
key to get the list of values to assign

5. MEL Context Objects
 Context Objects
 server: this object provides access to the fields for the
hardware, operating system, user, and network
interface.
 mule: this object provides access to the fields for your
Mule instance.
 app: this object provides access to the fields of your
Mule application.
 message: this object provides access to the fields of the
Mule message.

6. MEL Variables
 Variables
 flowVars
 sessionVars
 Usage
 flowVars
 #[flowVars.firstname = Karthik]
 sessionVars
 #[sessionVars.lastname = Selvaraj]

7. MEL Variable
 You can use the variable name directly in a MEL
expression
 #[firstname] is equivalent to #[flowVars.firstname]
 #[lastname] is equivalent to #[sessionVars.lastname]
 Mule assumes that it is a flowVars and, when MEL
evaluates the expression, looks for a variable by that
name. If Mule cannot find a flowVars by that name, it
looks for a sessionVars by that name before failing.

8. MEL Variable
 If you wish to disable this auto-resolution of variables
by name, please include the below flow configuration
xml
 <configuration> <expression-language
autoResolveVariables="false"/> </configuration>

9. MEL Variable

10. Reference
 https://docs.mulesoft.com/mule-user-
guide/v/3.7/mule-expression-language-mel
 https://docs.mulesoft.com/mule-user-
guide/v/3.6/mule-expression-language-basic-syntax
 https://docs.mulesoft.com/mule-user-
guide/v/3.6/mule-expression-language-reference
 https://docs.mulesoft.com/mule-user-
guide/v/3.6/mule-expression-language-examples
 https://docs.mulesoft.com/mule-user-
guide/v/3.7/mule-expression-language-tips

11. Reference
 http://blogs.mulesoft.com/wp-
content/uploads/2012/12/refcard-mel.pdf
 https://dzone.com/articles/mule-expression-
language-cheat

12. Mule Expression Language
THANK YOU