intro to websockets (in java)

WebSockets in JavaJonathan Freeman

@freethejazz

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WebSockets in Java


Jonathan Freeman @freethejazz

Overview



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● Gradients of client server communication● Intro to WebSockets● Implementing WebSockets

Client/Server Communication

{WebSockets in Java}




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Basic Web Applications



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Pros● Simple● Client gets what it wants(and when)● Minimal interaction between the server and the client

For the server, this is a highly reactive model. Sits around waiting until it gets a request, then delivers back whatever is needed.

Cons● Server cannot initiate the communication, only the client● new client request == new page load



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How do we add more interactionbetween the client and the server?



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Variations on the basic model● AJAX● Long-Polling

New models● SSE● WebSockets



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AJAX



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Pros● Simple● Client gets what it wants(and when)● Minimal interaction between the server and the client● Piecemeal approach adds value to the client● Client can update based on the response from the server without loading a new page.

For the server, this is a still highly reactive model. Sits around waiting until it gets a request, then delivers back whatever is needed.

Cons● Server cannot initiate the communication● New client request != new page load



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Long Polling



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Pros● Emulating a more real-time communication model from server to client.

Cons● Dealing with more longer and repeated connections, so you’ll have to account for that● It’s kind of a hack.



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Server-Sent Events



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Pros● A real-time communication model from server to client

Cons● Communication is only one way

Intro to WebSockets





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Pros● A real-time communication model

Cons● May be overkill for your particular application● Spec still being defined● Security vulnerabilities in previous implementation



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Why use WebSockets?



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● Chat applications● Instagram-like applications(social streams)● Financial tickers● Multiplayer games

Implementing WebSockets





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1. Create an endpoint class(programmatic or annotated)2. Override/annotate the lifecycle methods(depending on how you create the endpoint)3. Add your business logic4. Deploy!



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Creating the endpoint class

public class MyWebSocketEndoint extends Endpoint {

@Override

public void onOpen(final Session session, EndpointConfig config) {

session.addMessageHandler(new MessageHandler.Whole<String>() {

@Override

public void onMessage(String msg) {

try {

session.getBasicRemote().sendText(msg);

} catch (IOException e) { ... }

}

});

}

}



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MessageHandler methods to override:

onMessage



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ServerEndpointConfig.Builder.create(MySocketEndpoint.class,

"/mywebsocket").build();



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Creating the endpoint class

@ServerEndpoint("/mywebsocket")

public class MyWebSocketEndpoint {

@OnMessage

public void onMessage(Session session, String message) {

try {

//to do some work


}

}



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Possible Annotations:

@OnOpen@OnMessage@OnError@OnClose



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Sending a response to a single client



@OnMessage


RemoteEndpoint remote = session.getBasicRemote();

try {

remote.sendText(message);


}

}



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Sending a response to all connected clients



@OnMessage


try {

for (Session sess : session.getOpenSessions()) {

if (sess.isOpen())

sess.getBasicRemote().sendText(message);

}


}

}



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In Spring 4...



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@Controllerpublic class MyWebSocketController { @RequestMapping(value=”/mywebsocket”, method=POST) public void overHttp(String text) { // ... } @MessageMapping("/mywebsocket") public void overStomp(String text) { // ... }}

http://blog.gopivotal.com/products/websocket-architecture-in-spring-4-0http://assets.spring.io/wp/WebSocketBlogPost.html

http://blog.gopivotal.com/products/websocket-architecture-in-spring-4-0

http://blog.gopivotal.com/products/websocket-architecture-in-spring-4-0

http://assets.spring.io/wp/WebSocketBlogPost.html

http://assets.spring.io/wp/WebSocketBlogPost.html



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References:

https://www.openshift.com/blogs/how-to-build-java-websocket-applications-using-the-jsr-356-api

http://docs.oracle.com/javaee/7/tutorial/doc/websocket.htm







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Image Attribution:

client-server communication diagrams: http://stackoverflow.com/questions/11077857/what-are-long-polling-websockets-server-sent-events-sse-and-comet

http://stackoverflow.com/questions/11077857/what-are-long-polling-websockets-server-sent-events-sse-and-comet



Thank You



intro to websockets (in java)

Technology

java jonathan freeman

javaoverviewjonathan

client client

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client new client request

cons server

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