Mule ESB allows defining variables to store data. Variables can be flow variables, with scope limited to a flow, or session variables, with scope to the entire application. Lists and maps can be defined as Mule variables similarly to how they are defined in Java. A List variable can be set using #[{values}] or #[[values]] syntax. Map variables can be set using #[{key:value, key:value}] or #[['key':value, 'key':value]] syntax. Values can then be retrieved from List and Map variables using typical array/map syntax (e.g. flowVars['listVar'][0]).

2. Mule ESB has the ability to store data into variables.
Fortunately Mule offers 2 types of variables 1) Flow variables that has scope limited
to a flow and subflow and 2) Session variables that has scope and can be accessed
from entire application.
Now, one interesting facts I come across several Mule users is how to define a List
or a Map with a variable in Mule in the same way as Java.
Let me tell you, this is absolutely possible with Mule.
We can define List or a Map in Mule with Mule variables.

4. We can define a List with a Mule variable in following ways :-
<set-variable variableName="test" value="#[{1000,100,14,1}]" doc:name="Variable"/>
Or
<set-variable variableName="test" value="#[[1000,100,14,1]]" doc:name="Variable"/>
Here you can see we define a variable named as test which is defined as a List

5. Now, we can get the values from the List as follow :-
<logger level="INFO" message="#[flowVars['test'][0]]" doc:name="Logger"/>
<logger level="INFO" message="#[flowVars['test'][1]]" doc:name="Logger"/>
<logger level="INFO" message="#[flowVars['test'][2]]" doc:name="Logger"/>
<logger level="INFO" message="#[flowVars['test'][3]]" doc:name="Logger"/>
As you can see we are retrieving the values from the List with the index

6. Now, we can define a Map in the same way as follow :-
<set-variable variableName="customMap" value="#[{'k2':'new', 'k3':'v3'}]" />
Or
<set-variable variableName="customMap" value="#[['k2':'new', 'k3':'v3‘]]" />
Here you can see we define a variable named as customMap which is defined as a
Map

7. Now, we can get the values from the Map as follow :-
<logger message="#[flowVars['customMap']['k2']] " level="INFO"
doc:name="Logger"/>
<logger message="#[flowVars['customMap']['k3']] " level="INFO"
doc:name="Logger"/>
As you can see we are retrieving the values from the Map with the key

8. Now, let us consider a simple flow to demonstrate the List and the Map as follow :-

9. The Mule config will be :-
You can see here we are using Expression component to reassign our List value of index
1 and index 2 … Then we are using logger to print the new value of List again in the
console

10. So, if we test the example we will get all the value of List and Map variables as follow as
well as with new reassigned value :-

11. So, here you can see how to use a List and Map with Mule variable… Hope I was
clear enough to give an Idea of it’s implementation ….

12. In my next slide I will bring some other techniques in Mule implementation .
Hope you have enjoyed this simpler version.
Keep sharing your knowledge and let our Mule community grow 