This document discusses how to dynamically generate JSON payloads in Mule ESB flows. It shows how to use an expression transformer to create a JSON payload from flow variables and send it to an external service. The JSON payload is constructed programmatically using Mule expressions. The flow variables are used to set values in the JSON. Testing the flow by hitting a URL generates and posts the JSON, then logs the request and response. In this way dynamic JSON can be constructed and used to call external services in Mule.

1. Creating Dynamic JSON in Mule

2. Mule ESB has multiple options to create dynamic payload. The payload used in Mule can be of
multiple types like JSON, XML or simple Text payload.
With Mule we can dynamically generate any type of payload at any point of time in the flow.
We will see how to create a simple JSON payload dynamically within a Mule flow and post that JSON
to an external service and get a response.
It’s quite simple and we will see how we can generate a JSON in a flow.

4. Let us consider we need to create a JSON file as following :-
{
"myService": {
"messageHeader": {
"messageId": "ec75da88e64a739e12c126",
"messageDateTime": "2014-09-18T14:07:46+0530"
},
"mesageBody": {
"myServiceRequest": {
"Amount": 3520,
"ConsumerId": "ABC-T14005-AFF",
"Timestamp": "2014-10-27T18:36:18+0700"
}
}
}
}
Now, we need to create this flow in our Mule flow and send the JSON request created to the external service
and will get a response. We will assign the JSON elements value from flow variables for now, but you can use
message inbound properties or other ways to assign the flow variables dynamically within the flow.

5. We will use Mule Expression Transformer to create this JSON request. As per Mule documentation here
https://developer.mulesoft.com/docs/display/current/Expression+Transformer+Reference :-
The Expression Transformer executes one or more expressions on the current message. The results of these
expressions becomes the payload of the current message.

6. Let’s consider our Mule flow as following :-
Here you can see, the expression transformer is creating the JSON request which is send to the external web service. The
flow variables are used to set the value and you can assign the variables dynamically in your way.

7. Now let’s test our flow by placing by hitting the url http://localhost:8085/rc/test on browser as
follows, :-
The JSON request will be generated in the flow and with that request it will be posted to the external
web service which will return a response

8. Now, we can see in our logger the JSON request generated and the JSON response from the external
service in return :-

9. So, here you can see how to set a Dynamic JSON and can be send to the external service to get a
response…. you can try this with your requirement as well and set the value dynamically in the flow
variables or can use other dynamic options like inbound properties etc !!!….

10. 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 