natsub

A NATS subscribe api used on server

By creating a MessageProcessor with a NATS server ips, natsub is simply integrated with the Web socket server in Java. The front end like js can easily subscribe or dissubscrbe a topic or a type of topic with any number of id by sending message. There will be just one handler to communicate with NATS server shared by any number of sessions which subscribe the same topic.

Show me a demo

Here is a demo showing how it works.

How to setup

Setup server

The following code shows how to initialize the web socket server with natsub handlering the messages.

	package com.natsub.ws;

	import javax.websocket.CloseReason;
	import javax.websocket.OnClose;
	import javax.websocket.OnError;
	import javax.websocket.OnMessage;
	import javax.websocket.OnOpen;
	import javax.websocket.Session;
	import javax.websocket.server.ServerEndpoint;

	import org.apache.log4j.Logger;

	@ServerEndpoint(value = "/ws/wsservice")
	public class CIWebSocket {

		private static Logger log = Logger.getLogger(CIWebSocket.class);
		
		// parameter should be a string consist of nats server ips which is joined by ';'
		protected static MessageProcessor processor = new MessageProcessor("http://1.1.1.1:4222;http://2.2.2.2:4222");
		
		@OnOpen
		public void onOpen(Session session) {
			log.info("Client connected, session ID: " + session.getId());
		}
		
		@OnMessage
		public void onMessage(String message, Session session) {
			log.info("Client send: " + message);
			processor.onMessage(message, session);
		}
		
		@OnClose
		public void onClose(Session session, CloseReason reason) {
			log.info("Client disconnected, session ID: " + session.getId());
			processor.onClose(session, reason);
		}
		
		@OnError
		public void onError(Session session, Throwable e) {
			log.error("Error occurred! session ID: " + session.getId());
			processor.onError(session, e);
		}
	}

Configure topic

Configure topics in Enum TopicType under com.natsub.ws.Topic.java directly. Recently it just support hardcodely.

    EXAMPLE_TOPIC("1", "topic.example.prefix.", NatsHandler.class);

The first parameter is the type of the topic which is also the topic unique identification. The second parameter is the prefix of the topic name. It will be joined with id sent from client, then as a name to subscribe the topic from NATS. The last parameter is the handler to process the response from NATS. Now only NatsHandler is provided.

Web client

Firstly, the ws.js (which is under example/client) should be added in html. Then connect to the web socket server by code:

	WSManager().get_instance().connect('http://example.ws');

register message handler

	WSManager().get_instance().register_handler({
		type: "1",
		
		// process the message
		handle_message: function(message) {
		
		}
	})

Subscribe topic

Subscribe by specific ids 1, 2, 3:

	WSManager().get_instance().send_params({
		action: 'subscribe',
		type: '1',
		id: '1,2,3'
	})

Then it subscribe topic "topic.example.prefix.1", "topic.example.prefix.2" and "topic.example.prefix.3" . If the id is not provided, the name of subscribed topic will be "topic.example.prefix."

Unsubscribe topic

by id:

	WSManager().get_instance().send_params({
		action: 'unsubscribe',
		type: '1',
		id: '1,2,3'
	})

by type:

	WSManager().get_instance().send_params({
		action: 'unsubscribeType',
		type: '1'
	})

unsubscribe all topic related current session:

	WSManager().get_instance().send_params({
		action: 'unsubscribeAll'
	})