Mule 4 - JSON to String JSON - JavaScript

In Mule 4, you may encounter situations where you need to convert a JSON object to a plain string value. Luckily, the DataWeave language in Mule 4 provides an easy-to-use function to achieve this: write.

The write Function

The write function can be used to convert a JSON object to a string representation of JSON.

%dw 2.0
output application/json
---
{
    "name": "John",
    "age": 30,
    "email": "john@example.com"
} write ((_, p) -> p)

The write function accepts a transformer function as a second parameter, which determines how the output should be transformed. In this case, we are using a lambda function that takes two arguments: _ (an unused value) and p (the payload). This transformer function returns p, which means that the output of the write function is the string representation of the input JSON object.

Using write in a Mule Flow

Here is an example Mule flow that demonstrates how to use the write function to convert a JSON object to a string:

<flow name="json-to-string">
    <http:listener path="/json-to-string" allowedMethods="GET"/>
    <set-payload value='{"name": "John", "age": 30, "email": "john@example.com"}'/>
    <dw:transform-message doc:name="Transform Message">
        <dw:set-payload><![CDATA[%dw 2.0
output application/json
---
payload write ((_, p) -> p)]]></dw:set-payload>
    </dw:transform-message>
    <logger message="#[payload]" level="INFO" doc:name="Logger"/>
</flow>

In this flow, we first set the payload to a JSON object, then use the dw:transform-message component to convert the JSON object to a string using the write function. Finally, we log the output of this transformation.

Conclusion

Converting a JSON object to a string representation of JSON in Mule 4 is simple and easy thanks to the write function in DataWeave. Whether you are working with APIs or handling JSON data in any other way, this function is an essential tool to have in your toolbox.