UserWriter.java

package svanimpe.reminders.json;

import java.io.IOException;
import java.io.OutputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
import javax.json.Json;
import javax.json.JsonArrayBuilder;
import javax.json.JsonObjectBuilder;
import javax.json.JsonWriter;
import javax.ws.rs.Produces;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.ext.MessageBodyWriter;
import javax.ws.rs.ext.Provider;
import svanimpe.reminders.domain.Role;
import svanimpe.reminders.domain.User;

@Provider
@Produces(MediaType.APPLICATION_JSON)
public class UserWriter implements MessageBodyWriter<User>
{
    @Override
    public boolean isWriteable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType)
    {
        return User.class.isAssignableFrom(type);
    }

    @Override
    public long getSize(User user, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType)
    {
        return -1;
    }

    @Override
    public void writeTo(User user, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType, MultivaluedMap<String, Object> httpHeaders, OutputStream entityStream) throws IOException, WebApplicationException
    {
        JsonObjectBuilder jsonUser = Json.createObjectBuilder();

        jsonUser.add("username", user.getUsername());

        if (user.getFullName() != null) {
            jsonUser.add("fullName", user.getFullName());
        }

        JsonArrayBuilder roles = Json.createArrayBuilder();
        for (Role role : user.getRoles()) {
            roles.add(role.name());

        }
        jsonUser.add("roles", roles);

        try (JsonWriter writer = Json.createWriter(entityStream)) {
            writer.writeObject(jsonUser.build());
        }
    }
}