Flexible marshalling with JAXB

Question

I\'m hoping to have a flexible way of marshalling objects. A verbose version for single objects and a less-verbose version for multiple object versions.

For example, co

Answer 1

Note: I'm the EclipseLink JAXB (MOXy) lead, and a member of the JAXB 2 (JSR-222) expert group.

Your question is tagged EclipseLink, if you are using EclipseLink JAXB (MOXy) you can take advantage of the external binding document to apply a second mapping to the Department class.

---

ContextResolver

In a JAX-RS environment you can leverage MOXy's external binding document through a ContextResolver:

import java.io.*;
import java.util.*;     
import javax.ws.rs.Produces;
import javax.ws.rs.ext.*;
import javax.xml.bind.*;
import org.eclipse.persistence.jaxb.JAXBContextFactory;

@Provider
@Produces({"application/xml", "application/json"})
public class DepartmentContextResolver implements ContextResolver {

    private JAXBContext jc;

    public DepartmentContextResolver() {
        try {
            Map props = new HashMap(1);
            props.put(JAXBContextFactory.ECLIPSELINK_OXM_XML_KEY, "example/bindings.xml");
            jc = JAXBContext.newInstance(new Class[] {Department.class} , props);
        } catch(JAXBException e) {
            throw new RuntimeException(e);
        } 
    }

    public JAXBContext getContext(Class clazz) {
        if(Department.class == clazz) {
            return jc;
        }
        return null;
    }


} 

For More Information

• http://blog.bdoughan.com/2011/04/moxys-xml-metadata-in-jax-rs-service.html
• http://blog.bdoughan.com/2010/08/creating-restful-web-service-part-35.html

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External Binding Document

By default MOXy's external binding document is used to augment the annotated model, but if you set the xml-mapping-metadata-complete flag it will completely override the annotations allowing you to apply a completely different mapping:

    ...

For More Information

• http://blog.bdoughan.com/2011/09/mapping-objects-to-multiple-xml-schemas.html
• http://blog.bdoughan.com/2010/12/extending-jaxb-representing-annotations.html

UPDATE

This update is to address a number of questions you asked in one of your comments:

1 . Should/can each ContentResolver have its own binding file?

Yes each ContextResolver should have its own binding file. The main reason for introducing a new ContextResolver is to represent a secondary mapping.

2 . Can I have more than one for each ContentResolver (this would give me a number of renderings of the same class, creating a 'view' of sorts), perhaps specifying its location in the constructor?

For a single ContextResolver you can express the metadata across multiple binding files, but they will be combined into a single set of mappings. This means that a single ContentResolver cannot have multiple views of a single class. A separate ContextResolver is used to represent a secondary mapping.

3 . Where should the binding files reside?

I recommend loading the metadata file from the class path.

• http://blog.bdoughan.com/2011/04/moxys-xml-metadata-in-jax-rs-service.html

4 . I can see how the ContentResolver could be easily specified in a Resource's GET method, but how would this be done if the object is embedded in another (JPA) object? In the embedded object's getter/setter?

Your JAX-RS implementation should pick up your ContextResolver because it is annotated with @Provider. The ContextResolver used for a class will depend on how you implement the getContext method:

public JAXBContext getContext(Class clazz) {
    if(Customer.class == clazz) {
        return jc;
    }
    return null;
}