In case we want our Dataweave expression outside mule project, load and process it at runtime then you would need Dynamic Evaluate component.
In a scenario wherein dataweave mapping conditions are expected to change frequently based on client’s requirements and you don’t want to redeploy running APIs again and again, in such scenario we can store our dataweave expression in a DB or S3 or other location and access and process it dynamically in our Mule API. Any changes made to this external datawave will be picked up by Mule while reading it from external source and processed.
In the below example we are using variable dynamic_dw to store the datawave expression as a String. In a real world this datawave expression should be coming from an external source like DB or SFTP or others and getting stored in a variable.
<sub-flow name="dynamic-evaluateSub_Flow" doc:id="2145c3c0-5196-418f-9dd3-adf06966cc4a" > <set-variable value="#[%dw 2.0 output application/json --- payload]" doc:name="Store payload" doc:id="18b55a69-28fd-48ae-9344-f80e9be3ffc6" variableName="reqReceived"/> <set-variable value="#['%dw 2.0 output application/json --- vars.reqReceived.username']" doc:name="datawave received from external source" doc:id="29aebfba-73e4-41b3-9f3f-e508f98da413" variableName="dynamic_dw"/> <logger level="INFO" doc:name="datawave received" doc:id="672895f7-42e8-4c25-8dca-b11bd61634b3" message="#['script - ' ++ vars.dynamic_dw]"/> <ee:dynamic-evaluate doc:name="Dynamic Evaluate" doc:id="59d877bb-36ba-4193-bf72-df5083a06d22" expression="#[vars.dynamic_dw]"/> <logger level="INFO" doc:name="output" doc:id="fea7a7e5-b8d3-4726-80b8-a846c3794a71" message="#[payload]"/> </sub-flow>