Mule 3 How to Declare multiple flow variables - mule

Question

I am new to Mule and I am using Mule version 3.x. We can set values of variable using Set Variable Component. And using expression component, we can set multiple variables at a time. But expression component does not allow to Declare a flow variable. So I have to first use 3 Set Variable component and then use expression to set them at one go(if it needs to be changed).
In case of multiple variables, is there any way to declare and initialize variable in one component instead of having a separate Set Variable component to declare it?

Answer 1

The Message Properties Transformer
If you want to set multiple flow vars in a single component in Mule 3, and you don't need to do any transformation beforehand, the Message Properties transformer is probably the most succinct ways to do this. I like it because in addition to being able to set multiple flow vars in a single component, the XML is clear, and when you click on the component in AP Studio, the UI makes it immediately obvious that you're setting multiple variables with a single component. Just make sure to use scope="invocation" so that you're setting flow vars:
<message-properties-transformer scope="invocation" doc:name="Set flowVars">
<add-message-property key="varName1" value="1"/>
<add-message-property key="varName2" value="2"/>
<add-message-property key="varName3" value="2"/>
</message-properties-transformer>
If you need to do small transformations, you can always call DataWeave from MEL. Here's an example:
...
<add-message-property key="varName1" value="dw('payload map $.id')"/>
...
The Transform Message Component (DataWeave)
You can also do this in DataWeave with the Transform Message component as well. I do feel it has a couple disadvantages that I should point out, though. The first is the XML is more verbose and difficult to read:
<dw:transform-message doc:name="Transform Message">
<dw:set-variable variableName="varName1"><![CDATA[%dw 1.0
%output application/java
---
1]]></dw:set-variable>
<dw:set-variable variableName="varName2"><![CDATA[%dw 1.0
%output application/java
---
2]]></dw:set-variable>
<dw:set-variable variableName="varName3"><![CDATA[%dw 1.0
%output application/java
---
3]]></dw:set-variable>
</dw:transform-message>
In addition, there is no obvious way to tell from the AP Studio UI that this particular transform message component is setting multiple variables:

Answer 2

If you're using enterprise edition, please use dataweave to set multiple variables in one component.
Runtime 4.1
https://docs.mulesoft.com/mule-runtime/4.1/dataweave-variables
Runtime 3.8
https://docs.mulesoft.com/mule-runtime/3.8/dataweave

Answer 3

I would like to know why do you need to just declare variables. Anyways if in case you just need it blank while declaring, you can simply set it as below.
<expression-component doc:name="Expression">
<![CDATA[flowVars.var1 ="" ;
flowVars.var2="";]]>
</expression-component>
Hope this help.