How to serialize Java primitives using Jersey REST

Question

In my application I use Jersey REST to serialize complex objects. This works quite fine. But there are a few method which simply return an int or boolean.

Jersey can

Answer 1

I had the same problem today and didn't give up until i found a really good suitable solution. I can not update the jersey library from 1.1.5 it is a Legacy System. My Rest Service returns a List and they should follow those rules.

1. Empty Lists are rendered as [] (almost impossible)
2. One Element Lists are rendered as [] (difficult but only mapping configuration)
3. Many Element Lists are rendered as [] (easy)

Start from easy to impossible.

3) nothing today normal JSON Mapping

2) Register JAXBContextResolver like the following

@Provider
public class JAXBContextResolver implements ContextResolver {
    private final JAXBContext context;
    private final Set> types;
    private Class[] ctypes = { Pojo.class }; //your pojo class
    public JAXBContextResolver() throws Exception {
        this.types = new HashSet>(Arrays.asList(ctypes));
        this.context = new JSONJAXBContext(JSONConfiguration.mapped()
                .rootUnwrapping(true)
                .arrays("propertyName") //that should rendered as JSONArray even if the List only contain one element but doesn't handle the empty Collection case
                .build()
                , ctypes);
    }

    @Override
    public JAXBContext getContext(Class objectType) {
        return (types.contains(objectType)) ? context : null;
    }
}

1) The following approach only works for Collections$EmptyList class. May you find a way to make it general for all Collections they are empty. May code deal with EmptyList so.

@Provider
@Produces(value={MediaType.APPLICATION_JSON})
public class EmptyListWriter implements MessageBodyWriter {

    private static final String EMPTY_JSON_ARRAY = "[]";

    @Override
    public long getSize(AbstractList list, Class clazz, Type type, Annotation[] annotations, MediaType mediaType) {
        return EMPTY_JSON_ARRAY.length();
    }

    @Override
    public boolean isWriteable(Class clazz, Type type, Annotation[] annotations, MediaType mediaType) {
        return clazz.getName().equals("java.util.Collections$EmptyList");
    }

    @Override
    public void writeTo(AbstractList list, Class clazz, Type type, Annotation[] annotations, MediaType mediaType, 
            MultivaluedMap headers, OutputStream outputStream) throws IOException, WebApplicationException {
        if (list.isEmpty())
            outputStream.write(EMPTY_JSON_ARRAY.getBytes());            
    }
}