Migrating the JSON Module

This version of Mule reached its End of Life Leaving the Site on May 2, 2023, when Extended Support ended.

Deployments of new applications to CloudHub that use this version of Mule are no longer allowed. Only in-place updates to applications are permitted.

MuleSoft recommends that you upgrade to the latest version of Mule 4 that is in Standard Support so that your applications run with the latest fixes and security enhancements.

A new JSON module in Mule 4 replaces the one that was bundled in with Mule 3 for schema validation.

To migrate transformations involving JSON, MuleSoft recommends that you use DataWeave.

Migrating Transformers

In Mule 3, many components required the payload to be a POJO so that its fields could be accessed. In Mule 4, DataWeave can be used as a query language directly on the JSON payload, which completely avoids the need to convert the payload to a POJO as an intermediate step.

JSON to Object Transformer

For mapping rules that are configured for the json:json-to-object-transformer, you can express the rules in DataWeave.

In Mule 3:

Example: Mixin used in the Mapper Configuration

public abstract class AppleMixin
{
    AppleMixin(@JsonProperty("bitten") boolean wasBitten)
    {
        super();
    }

}java

Example: Transformer Referencing the Mapper

<json:mapper name="myMapper">
    <json:mixin mixinClass="org.mule.module.json.transformers.AppleMixin"
                    targetClass="org.mule.tck.testmodels.fruit.Apple"/>
</json:mapper>

<flow name="flow">
    <json:json-to-object-transformer returnClass="org.mule.tck.testmodels.fruit.Apple"
                                     mapper-ref="myMapper"/>
</flow>xml

In Mule 4:

Example: Using DataWeave as the Mapper

<flow name="flow">
    <ee:transform>
        <ee:message>
            <ee:set-payload>
                <![CDATA[%dw 2.0
                    type apple = Object { class: "org.mule.tck.testmodels.fruit.Apple"}
                    output application/java
                    ---
                    {
                        wasBitten = bitten
                    } as apple
                ]]>
            </ee:set-payload>
        </ee:message>
    </ee:transform>
</flow>xml

You don’t have to define a mapper or a mixin class in Mule 4. The mapping rules are defined using DataWeave code.

Object to JSON Transformer

The mapping rules for the json:object-to-json-transformer are also expressed using DataWeave:

In Mule 3:

Example: Transformer with Mixins

<flow name="flow">
    <json:object-to-json-transformer returnClass="org.mule.tck.testmodels.fruit.Apple">
        <json:serialization-mixin mixinClass="org.mule.module.json.transformers.AppleMixin"
                                  targetClass="org.mule.tck.testmodels.fruit.Apple"/>

    </json:object-to-json-transformer>
</flow>xml

In Mule 4:

Example: Using DataWeave as the Mapper

<flow name="flow">
    <ee:transform>
        <ee:message>
            <ee:set-payload>
                <![CDATA[%dw 2.0
                    output application/json
                    ---
                    {
                        bitten = wasBitten
                    }
                ]]>
            </ee:set-payload>
        </ee:message>
    </ee:transform>
</flow>xml

In Mule 4 you can set the output format in the transformation. In this case, the expression defines the output as application/json, so the transformation function returns a JSON payload.

Migrating XSLT Operations

In Mule 4, the JSON module does not provide a component that transforms the JSON based on an XSLT mapping. Possible ways to handle this case are:

Migrate the XSLT to a DataWeave transformation (recommended)
Use XSLT support of the XML module, first converting the payload to XML.

Mule 4 Example: Using XSLT to Transform JSON

<flow name="flow">
    ...
	<xml-module:xslt-transform>
	    <xml-module:content>#[output application/xml --- payload]</xml-module:content>
	    <xml-module:xslt>
	        (the XSLT transformation) ...
	    </xml-module:xslt>
	</xml-module:xslt-transform>
	...
</flow>xml

Migrating the JSON Module

Migrating Transformers

JSON to Object Transformer

Object to JSON Transformer

Migrating XSLT Operations

See also