Mule object-to-json-transformer: how to exclude nulls? - mule

Question

Is there a way to instruct Mule object-to-json-transformer component to not include null properties into the JSON produced?
By default it produces something like this for null object properties:
"value": null
Thank you,
ps. just wanna clarify that I'm looking for a way to configure this in Mule, not by using the classes jackson annotations.

Answer 1

Ok, I've found the answer.
Mule object-to-json transformer is ignoring jackson annotations.
Instead, you need to define a customized object mapper bean like this:
<spring:beans>
<spring:bean id="Bean" name="NonNullMapper" class="org.codehaus.jackson.map.ObjectMapper">
<spring:property name="SerializationInclusion">
<spring:value type="org.codehaus.jackson.map.annotate.JsonSerialize.Inclusion">NON_NULL</spring:value>
</spring:property>
</spring:bean>
</spring:beans>
and then reference the bean in the transformer like this:
<json:object-to-json-transformer doc:name="Object to JSON" mapper-ref="NonNullMapper"/>
Note, that this approach only works with custom java classes.

Answer 2

Goes with this, #JsonSerialize (include = JsonSerialize.Inclusion.NON_NULL), simply place it in its class. The library to import is import org.codehaus.jackson.map.annotate.JsonSerialize.

Answer 3

You can configure the ObjectMapper that the json transformers use like so:
<spring:beans>
<spring:bean id="jacksonObjectMapper" class="org.codehaus.jackson.map.ObjectMapper" />
<spring:bean
class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
<spring:property name="targetObject" ref="jacksonObjectMapper" />
<spring:property name="targetMethod" value="configure" />
<spring:property name="arguments">
<spring:list>
<spring:value>WRITE_NULL_VALUES</spring:value>
<spring:value>false</spring:value>
</spring:list>
</spring:property>
</spring:bean>
</spring:beans>
<flow name="json" >
...
<json:object-to-json-transformer mapper-ref="jacksonObjectMapper" />
</flow>
Or if you are using a Map:
<spring:beans>
<spring:bean id="jacksonObjectMapper" class="org.codehaus.jackson.map.ObjectMapper" />
<spring:bean
class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
<spring:property name="targetObject" ref="jacksonObjectMapper" />
<spring:property name="targetMethod" value="configure" />
<spring:property name="arguments">
<spring:list>
<spring:value>WRITE_NULL_MAP_VALUES</spring:value>
<spring:value>false</spring:value>
</spring:list>
</spring:property>
</spring:bean>
</spring:beans>
<flow name="json" >
...
<json:object-to-json-transformer mapper-ref="jacksonObjectMapper" />
</flow>