source: src/main/java/geniusweb/profilesserver/websocket/GetProfileSocket.java@ 6

package geniusweb.profilesserver.websocket;

import java.io.IOException;

import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.PathParam;
import javax.websocket.server.ServerEndpoint;

import com.fasterxml.jackson.databind.ObjectMapper;

import geniusweb.profile.Profile;
import geniusweb.profilesserver.ProfilesFactory;
import geniusweb.profilesserver.events.ChangeEvent;
import tudelft.utilities.listener.Listener;

/**
 * Returns a websocket that communicates the list of currently available domains
 * and profiles. Every time something changes, a new list of domains and
 * profiles is sent. For each new websocket the server will create one of this
 * but they all share one {@link ProfilesFactory}.
 */
@ServerEndpoint("/websocket/get/{domain}/{profile}")
public class GetProfileSocket {
        private final static ObjectMapper jackson = new ObjectMapper();
        private Profile prof = null; // the latest that we sent to client.

        // should all be final, except that we can only set them when start is
        // called...
        private String profilename;
        private Listener<ChangeEvent> changeListener;
        private Session session;

        @OnOpen
        public void start(Session session, @PathParam("domain") final String domain,
                        @PathParam("profile") final String profile) throws IOException {
                this.session = session;
                this.profilename = domain + "/" + profile;

                changeListener = new Listener<ChangeEvent>() {
                        @Override
                        public void notifyChange(ChangeEvent data) {
                                sendupdatedProfile();
                        }
                };
                sendupdatedProfile();
                Profiles.factory.addListener(changeListener);
        }

        private void sendupdatedProfile() {
                Profile newprof = Profiles.factory.getProfile(profilename);
                // notice, may be null if profile does not exist/was removed.
                if (newprof == null ? prof != null : !newprof.equals(prof)) {
                        prof = newprof;
                        try {
                                session.getBasicRemote()
                                                .sendText(jackson.writeValueAsString(prof));
                        } catch (Exception e) {
                                e.printStackTrace();
                        }
                }
        }

        @OnClose
        public void end() throws IOException {
                Profiles.factory.removeListener(changeListener);
        }

        @OnError
        public void onError(Throwable t) throws Throwable {
                t.printStackTrace();
        }

}