I have a class that I would like to expose through a Jersey RESTful API. It looks similar to this:
@XmlRootElement
public class Data {
public String firstName;
public String lastName;
}
My problem is that these fields may be null, in which case the field is omitted from the JSON output. I would like all fields to be present regardless of their value. For example, if lastName is null, the JSON output will be:
{
"firstName" : "Oleksi"
}
instead of what I want:
{
"firstName" : "Oleksi",
"lastName" : null
}
I have a JAXBContextResolver (an implementation of ContextResolver) that looks like this:
@Provider
public class JAXBContextResolver implements ContextResolver<JAXBContext> {
// internal state
private final JAXBContext context;
private final Set<Class> types;
private final Class[] cTypes = { Data.class };
public JAXBContextResolver()
throws Exception {
types = new HashSet(Arrays.asList(cTypes));
context = new JSONJAXBContext(JSONConfiguration.natural().humanReadableFormatting(true).build(), cTypes);
}
@Override
public JAXBContext getContext(Class<?> objectType) {
return (types.contains(objectType)) ? context : null;
}
}
I've been trying to figure out how to get that desired output for a while, but I've had no luck. I'm open to trying other ContextResolvers/Serializers, but I haven't been able to find one that works, so code examples would be nice.
For EclipseLink JAXB (MOXy)'s JSON binding, the correct mapping would be the following. You could try it with your provider to see if it would work also:
@XmlRootElement
public class Data {
@XmlElement(nillable=true)
public String firstName;
@XmlElement(nillable=true)
public String lastName;
}
For More Information
UPDATE 2
EclipseLink 2.4 includes MOXyJsonProvider
which is an implementation of MessageBodyReader
/MessageBodyWriter
that you can use directly to leverage MOXy's JSON binding
UPDATE 1
The following MessageBodyReader
/MessageBodyWriter
may work better for you:
import java.io.*;
import java.lang.annotation.Annotation;
import java.lang.reflect.*;
import javax.xml.transform.stream.StreamSource;
import javax.ws.rs.*;
import javax.ws.rs.core.*;
import javax.ws.rs.ext.*;
import javax.xml.bind.*;
import org.eclipse.persistence.jaxb.JAXBContextFactory;
@Provider
@Produces(MediaType.APPLICATION_JSON)
@Consumes(MediaType.APPLICATION_JSON)
public class MOXyJSONProvider implements
MessageBodyReader<Object>, MessageBodyWriter<Object>{
@Context
protected Providers providers;
public boolean isReadable(Class<?> type, Type genericType,
Annotation[] annotations, MediaType mediaType) {
return true;
}
public Object readFrom(Class<Object> type, Type genericType,
Annotation[] annotations, MediaType mediaType,
MultivaluedMap<String, String> httpHeaders, InputStream entityStream)
throws IOException, WebApplicationException {
try {
Class<?> domainClass = getDomainClass(genericType);
Unmarshaller u = getJAXBContext(domainClass, mediaType).createUnmarshaller();
u.setProperty("eclipselink.media-type", mediaType.toString());
u.setProperty("eclipselink.json.include-root", false);
return u.unmarshal(new StreamSource(entityStream), domainClass).getValue();
} catch(JAXBException jaxbException) {
throw new WebApplicationException(jaxbException);
}
}
public boolean isWriteable(Class<?> type, Type genericType,
Annotation[] annotations, MediaType mediaType) {
return true;
}
public void writeTo(Object object, Class<?> type, Type genericType,
Annotation[] annotations, MediaType mediaType,
MultivaluedMap<String, Object> httpHeaders,
OutputStream entityStream) throws IOException,
WebApplicationException {
try {
Class<?> domainClass = getDomainClass(genericType);
Marshaller m = getJAXBContext(domainClass, mediaType).createMarshaller();
m.setProperty("eclipselink.media-type", mediaType.toString());
m.setProperty("eclipselink.json.include-root", false);
m.marshal(object, entityStream);
} catch(JAXBException jaxbException) {
throw new WebApplicationException(jaxbException);
}
}
public long getSize(Object t, Class<?> type, Type genericType,
Annotation[] annotations, MediaType mediaType) {
return -1;
}
private JAXBContext getJAXBContext(Class<?> type, MediaType mediaType)
throws JAXBException {
ContextResolver<JAXBContext> resolver
= providers.getContextResolver(JAXBContext.class, mediaType);
JAXBContext jaxbContext;
if(null == resolver || null == (jaxbContext = resolver.getContext(type))) {
return JAXBContextFactory.createContext(new Class[] {type}, null);
} else {
return jaxbContext;
}
}
private Class<?> getDomainClass(Type genericType) {
if(genericType instanceof Class) {
return (Class<?>) genericType;
} else if(genericType instanceof ParameterizedType) {
return (Class<?>) ((ParameterizedType) genericType).getActualTypeArguments()[0];
} else {
return null;
}
}
}
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