Chapter 156. JacksonXML DataFormat

The JacksonXML dataformat supports 15 options which are listed below.

        <dataFormats>
            <!-- here we define a Xml data format with the id jack and that it should use the TestPojo as the class type when
                 doing unmarshal. The unmarshalTypeName is optional, if not provided Camel will use a Map as the type -->
            <jacksonxml id="jack" unmarshalTypeName="org.apache.camel.component.jacksonxml.TestPojo"/>
        </dataFormats>

       <route>
            <from uri="direct:back"/>
            <unmarshal ref="jack"/>
            <to uri="mock:reverse"/>
        </route>

When marshalling a POJO to XML you might want to exclude certain fields from the XML output. With Jackson you can use JSON views to accomplish this. First create one or more marker classes.

Use the marker classes with the @JsonView annotation to include/exclude certain fields. The annotation also works on getters.

Finally use the Camel JacksonXMLDataFormat to marshall the above POJO to XML.

Note that the weight field is missing in the resulting XML:

<pojo age="30" weight="70"/>

As an example of using this attribute you can instead of:

JacksonXMLDataFormat ageViewFormat = new JacksonXMLDataFormat(TestPojoView.class, Views.Age.class);
from("direct:inPojoAgeView").
  marshal(ageViewFormat);

Directly specify your JSON view inside the Java DSL as:

from("direct:inPojoAgeView").
  marshal().jacksonxml(TestPojoView.class, Views.Age.class);

And the same in XML DSL:

<from uri="direct:inPojoAgeView"/>
  <marshal>
    <jacksonxml unmarshalTypeName="org.apache.camel.component.jacksonxml.TestPojoView" jsonView="org.apache.camel.component.jacksonxml.Views$Age"/>
  </marshal>

If you want to marshal a pojo to XML, and the pojo has some fields with null values. And you want to skip these null values, then you need to set either an annotation on the pojo, 

@JsonInclude(Include.NON_NULL)
public class MyPojo {
   ...
}

But this requires you to include that annotation in your pojo source code. You can also configure the Camel JacksonXMLDataFormat to set the include option, as shown below:

JacksonXMLDataFormat format = new JacksonXMLDataFormat();
format.setInclude("NON_NULL");

Or from XML DSL you configure this as

    <dataFormats>
      <jacksonxml id="jacksonxml" include="NOT_NULL"/>
    </dataFormats>

If you use jackson to unmarshal XML to POJO, then you can now specify a header in the message that indicate which class name to unmarshal to.
The header has key CamelJacksonUnmarshalType if that header is present in the message, then Jackson will use that as FQN for the POJO class to unmarshal the XML payload as.

 For JMS end users there is the JMSType header from the JMS spec that indicates that also. To enable support for JMSType you would need to turn that on, on the jackson data format as shown:

JacksonDataFormat format = new JacksonDataFormat();
format.setAllowJmsType(true);

Or from XML DSL you configure this as

    <dataFormats>
      <jacksonxml id="jacksonxml" allowJmsType="true"/>
    </dataFormats>

If you are using Jackson to unmarshal XML to a list of map/pojo, you can now specify this by setting useList="true" or use the org.apache.camel.component.jacksonxml.ListJacksonXMLDataFormat. For example with Java you can do as shown below:

JacksonXMLDataFormat format = new ListJacksonXMLDataFormat();
// or
JacksonXMLDataFormat format = new JacksonXMLDataFormat();
format.useList();
// and you can specify the pojo class type also
format.setUnmarshalType(MyPojo.class);

And if you use XML DSL then you configure to use list using useList attribute as shown below:

    <dataFormats>
      <jacksonxml id="jack" useList="true"/>
    </dataFormats>

And you can specify the pojo type also

    <dataFormats>
      <jacksonxml id="jack" useList="true" unmarshalTypeName="com.foo.MyPojo"/>
    </dataFormats>

You can use custom Jackson modules by specifying the class names of those using the moduleClassNames option as shown below.

    <dataFormats>
      <jacksonxml id="jack" useList="true" unmarshalTypeName="com.foo.MyPojo" moduleClassNames="com.foo.MyModule,com.foo.MyOtherModule"/>
    </dataFormats>

When using moduleClassNames then the custom jackson modules are not configured, by created using default constructor and used as-is. If a custom module needs any custom configuration, then an instance of the module can be created and configured, and then use modulesRefs to refer to the module as shown below:

    <bean id="myJacksonModule" class="com.foo.MyModule">
      ... // configure the module as you want
    </bean>
 
    <dataFormats>
      <jacksonxml id="jacksonxml" useList="true" unmarshalTypeName="com.foo.MyPojo" moduleRefs="myJacksonModule"/>
    </dataFormats>

 Multiple modules can be specified separated by comma, such as moduleRefs="myJacksonModule,myOtherModule"

Jackson has a number of features you can enable or disable, which its ObjectMapper uses. For example to disable failing on unknown properties when marshalling, you can configure this using the disableFeatures:

 <dataFormats>
      <jacksonxml id="jacksonxml" unmarshalTypeName="com.foo.MyPojo" disableFeatures="FAIL_ON_UNKNOWN_PROPERTIES"/>
 </dataFormats>

You can disable multiple features by separating the values using comma. The values for the features must be the name of the enums from Jackson from the following enum classes

To enable a feature use the enableFeatures options instead.

From Java code you can use the type safe methods from camel-jackson module:

JacksonDataFormat df = new JacksonDataFormat(MyPojo.class);
df.disableFeature(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
df.disableFeature(DeserializationFeature.FAIL_ON_NULL_FOR_PRIMITIVES);

Jackson ObjectMapper can be used to convert maps to POJO objects. Jackson component comes with the data converter that can be used to convert java.util.Map instance to non-String, non-primitive and non-Number objects.

Map<String, Object> invoiceData = new HashMap<String, Object>();
invoiceData.put("netValue", 500);
producerTemplate.sendBody("direct:mapToInvoice", invoiceData);
...
// Later in the processor
Invoice invoice = exchange.getIn().getBody(Invoice.class);

If there is a single ObjectMapper instance available in the Camel registry, it will used by the converter to perform the conversion. Otherwise the default mapper will be used.  

Using the prettyPrint option one can output a well formatted XML while marshalling:

 <dataFormats>
      <jacksonxml id="jack" prettyPrint="true"/>
 </dataFormats>

And in Java DSL:

from("direct:inPretty").marshal().jacksonxml(true);

Please note that there are 5 different overloaded jacksonxml() DSL methods which support the prettyPrint option in combination with other settings for unmarshalType, jsonView etc. 

To use Jackson XML in your camel routes you need to add the dependency on camel-jacksonxml which implements this data format.

If you use maven you could just add the following to your pom.xml, substituting the version number for the latest & greatest release (see the download page for the latest versions).

<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-jacksonxml</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>