MOXyJsonProvider not working

Question

In my REST applications (under GlassFish 4.1.2) I want to convert POJOs to JSON and back again. The examples all make it look easy but I am missing something.

Here is my application:

@ApplicationPath("/")
public class RootApp extends Application {

    @Override
    public Set<Class<?>> getClasses() {
        HashSet set = new HashSet<Class<?>>();
        set.add(HelloWorld.class);
        return set;
    }

    @Override
    public Set<Object> getSingletons() {
        HashSet set = new HashSet<Object>();

        MOXyJsonProvider moxyJsonProvider = new MOXyJsonProvider();
        moxyJsonProvider.setFormattedOutput(true);
        set.add(moxyJsonProvider);

        return set;
    }
}

And here is the Resource:

@Path("helloworld")
public class HelloWorld {

    private static int counter = 1;

    @GET
    @Produces(MediaType.APPLICATION_JSON)
    public Response getInevitableMessage() {    
        JsonHello hj = new JsonHello("Hello World", counter++);    
        return Response.ok(hj).build();
    }    
}

And last and least is the POJO to convert to and from JSON:

public class JsonHello {

    private int count;
    private String message;

    public JsonHello(String message, int count) {
        this.message = message;
        this.count = count;
    }

    public int count() { return count; }
    public void count(int value) { count = value; }

    public String message() { return message; }
    public void message(String value) { message = value; }
}

I am referring to the tagged answer in this thread. When I attempt to access "/helloworld" it pitches the following exception:

org.glassfish.jersey.server.ContainerException: java.lang.NoClassDefFoundError: Could not initialize class org.eclipse.persistence.jaxb.BeanValidationHelper

This application works if the resource just returns a string. There is nothing in the web.xml file since I am letting Glassfish set the application via its decorators.

Any idea what I am missing here?

Answer 1

I ended up solving the problem using the direction that @peeskillet suggested. MOXyJsonProvider is unneeded.

One problem that is hard to address is that almost all the examples on the web assume you are configuring your Servlet with a web.xml file, which I am not. All the configuration I do is from inside the Application object. The Jersey documentation does not make this very clear. What ends up working is this:

@Override
public Set<Class<?>> getClasses() {
    HashSet set = new HashSet<Class<?>>();
    set.add(JacksonFeature.class);
    set.add(MyObjectMapperProvider.class);
    set.add(Home.class);
    set.add(HelloWorld.class);
    return set;
}

At this point the REST resources can produce and consume various POJOs which are transcoded into JSON perfectly and without any effort.

Instead of just deleting this question I will put this answer here in hopes of saving someone the amount of time I spent finding this out.