Intro to WebSockets (in Java)

{CJUG}

WebSockets in Java
Jonathan Freeman
@freethejazz
{Open Software Integrators} { www.osintegrators.com} {@osintegrators}

WebSockets in Java

Open Software Integrators
●

Jonathan Freeman
@freethejazz

Founded January 2008 by Andrew C. Oliver
○ Durham, NC

Revenue and staff has at least doubled every year since
2009.
●

New office (2012) in Chicago, IL
○ We're hiring associate to senior level as well as UI Developers
(JQuery, Javascript, HTML, CSS)
○ Up to 50% travel (probably less), salary + bonus, 401k, health,
etc etc
○ Preferred: Java, Tomcat, JBoss, Hibernate, Spring, RDBMS,
JQuery
○ Nice to have: Hadoop, Neo4j, MongoDB, Ruby a/o at least one
Cloud platform


WebSockets in Java

Overview

Jonathan Freeman
@freethejazz

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


{WebSockets in Java}

Client/Server
Communication


WebSockets in Java
Jonathan Freeman
@freethejazz

Basic Web Applications


WebSockets in Java
Jonathan Freeman
@freethejazz


WebSockets in Java
Jonathan Freeman
@freethejazz

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


WebSockets in Java
Jonathan Freeman
@freethejazz

How do we add more interaction
between the client and the server?


WebSockets in Java
Jonathan Freeman
@freethejazz

Variations on the basic model
● AJAX
● Long-Polling
New models
● SSE
● WebSockets


WebSockets in Java
Jonathan Freeman
@freethejazz

AJAX


WebSockets in Java
Jonathan Freeman
@freethejazz

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


WebSockets in Java
Jonathan Freeman
@freethejazz

Long Polling


WebSockets in Java
Jonathan Freeman
@freethejazz

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.


WebSockets in Java
Jonathan Freeman
@freethejazz

Server-Sent Events


WebSockets in Java
Jonathan Freeman
@freethejazz

Pros
●

A real-time communication model from server to client

Cons
●

Communication is only one way



Intro to
WebSockets


WebSockets in Java
Jonathan Freeman
@freethejazz

Pros
●

A real-time communication model

Cons
●
●
●

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


WebSockets in Java
Jonathan Freeman
@freethejazz

Why use WebSockets?


WebSockets in Java
Jonathan Freeman
@freethejazz

●
●
●
●

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



Implementing
WebSockets


WebSockets in Java
Jonathan Freeman
@freethejazz

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 logic
4. Deploy!


WebSockets in Java
Jonathan Freeman
@freethejazz
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) { ... }
}
});
}
}

WebSockets in Java
Jonathan Freeman
@freethejazz

MessageHandler methods to override:
onMessage


WebSockets in Java
Jonathan Freeman
@freethejazz

ServerEndpointConfig.Builder.create(MySocketEndpoint.class,
"/mywebsocket").build();


WebSockets in Java
Jonathan Freeman
@freethejazz
Creating the endpoint class
@ServerEndpoint("/mywebsocket")
public class MyWebSocketEndpoint {
@OnMessage
public void onMessage(Session session, String message) {
try {
//to do some work
}
}


WebSockets in Java
Jonathan Freeman
@freethejazz

Possible Annotations:
@OnOpen
@OnMessage
@OnError
@OnClose


WebSockets in Java
Jonathan Freeman
@freethejazz
Sending a response to a single client
@OnMessage
RemoteEndpoint remote = session.getBasicRemote();
try {
remote.sendText(message);
}
}


WebSockets in Java
Jonathan Freeman
@freethejazz
Sending a response to all connected clients
@OnMessage
try {
for (Session sess : session.getOpenSessions()) {
if (sess.isOpen())
sess.getBasicRemote().sendText(message);
}
}
}


WebSockets in Java
Jonathan Freeman
@freethejazz

In Spring 4...


WebSockets in Java
Jonathan Freeman
@freethejazz

@Controller
public 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-4-0
http://assets.spring.io/wp/WebSocketBlogPost.html


WebSockets in Java
Jonathan Freeman
@freethejazz

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


WebSockets in Java
Jonathan Freeman
@freethejazz
Image Attribution:
client-server communication diagrams: http://stackoverflow.com/questions/11077857/what-are-longpolling-websockets-server-sent-events-sse-and-comet



Thank You


Intro to WebSockets (in Java)

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