How do I request a subset of XMLElements using MOXy? - rest

Question

I have a RESTful service that needs to return only a few of the XmlElements if "selectors" are submitted with the request. The URL will take the form of:
/merchants/{merchantId}/profile?selectors=<field1|field2|....|fieldN>
The selectors are optional, and so far I have implemented the service for the full set of elements to be returned for {merchantId} without selectors specified. Now I'm trying to figure out how to add in this added functionality. I'm sure this is covered in documentation but I can't find where. Any RTFM pointers would be appreciated. Thanks.

Answer 1

EclipseLink JAXB (MOXy) does not currently offer a mechanism to selectively indicate which fields/properties are included on a per marshal operation. This sounds like an interesting use case. I would appreciate if you could enter this as an enhancement request using the following link:
https://bugs.eclipse.org/bugs/enter_bug.cgi?product=EclipseLink
Below is an example of how you could use a stateful XmlAdapter to implement this use case by exploiting the fact that a JAXB (JSR-222) will not marshal an element when the value is null (see: http://blog.bdoughan.com/2012/04/binding-to-json-xml-handling-null.html).
FieldAdapter
Since we are going to leverage stateful XmlAdapters we're going to need one per field. Since all our XmlAdapters will perform the same logic we can create a super class that the others can extend from.
package forum13094195;
import javax.xml.bind.annotation.adapters.XmlAdapter;
public class FieldAdapter<T> extends XmlAdapter<T, T> {
private boolean include;
public FieldAdapter() {
this.include = true;
}
public FieldAdapter(boolean include) {
this.include = include;
}
#Override
public T marshal(T value) throws Exception {
if(include) {
return value;
}
return null;
}
#Override
public T unmarshal(T value) throws Exception {
return value;
}
}
Field1Adapter
package forum13094195;
public class Field1Adapter extends FieldAdapter<String> {
public Field1Adapter() {}
public Field1Adapter(boolean include) {
super(include);
}
}
Field2Adapter
package forum13094195;
public class Field2Adapter extends FieldAdapter<Integer>{
public Field2Adapter() {}
public Field2Adapter(boolean include) {
super(include);
}
}
Field3Adapter
package forum13094195;
public class Field3Adapter extends FieldAdapter<String> {
public Field3Adapter() {}
public Field3Adapter(boolean include) {
super(include);
}
}
Merchant
The #XmlJavaTypeAdapter annotation is used to specify an XmlAdapter on a field/property.
package forum13094195;
import javax.xml.bind.annotation.*;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
#XmlRootElement
#XmlAccessorType(XmlAccessType.FIELD)
public class Merchant {
#XmlJavaTypeAdapter(Field1Adapter.class)
String field1;
#XmlJavaTypeAdapter(Field2Adapter.class)
int field2;
#XmlJavaTypeAdapter(Field3Adapter.class)
String field3;
}
Demo
The demo code below demonstrates how to set a stateful XmlAdapter on the Marshaller.
package forum13094195;
import javax.xml.bind.*;
public class Demo {
public static void main(String[] args) throws Exception {
JAXBContext jc = JAXBContext.newInstance(Merchant.class);
Merchant merchant = new Merchant();
merchant.field1 = "A";
merchant.field2 = 2;
merchant.field3 = "C";
Marshaller marshaller = jc.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.marshal(merchant, System.out);
marshaller.setAdapter(new Field1Adapter(false));
marshaller.setAdapter(new Field2Adapter(false));
marshaller.setAdapter(new Field3Adapter(true));
marshaller.marshal(merchant, System.out);
}
}
Output
Below is the output from running the demo code. By default the entire object is marshalled out. The second document marshalled does not contain the fields we excluded.
<?xml version="1.0" encoding="UTF-8"?>
<merchant>
<field1>A</field1>
<field2>2</field2>
<field3>C</field3>
</merchant>
<?xml version="1.0" encoding="UTF-8"?>
<merchant>
<field3>C</field3>
</merchant>

Answer 2

Note: I'm the EclipseLink JAXB (MOXy) lead and a member of the JAXB (JSR-222) expert group.
In EclipseLink 2.5.0 we released a new feature called Object Graphs that enables you to marshal/unmarshal a subset of mapped fields/properties.
// Create the Object Graph
ObjectGraph subset = JAXBHelper.getJAXBContext(jc).createObjectGraph(Merchant.class);
subset.addAttributeNodes("field1", "field1", "fieldN");
// Output XML - Based on Object Graph
marshaller.setProperty(MarshallerProperties.OBJECT_GRAPH, subset);
marshaller.marshal(customer, System.out);
For More Information
http://blog.bdoughan.com/2013/03/moxys-object-graphs-partial-models-on.html