1.
WebSockets in Java
From n00b to pro
22 Dec 2013, JavaDay, Pance Cavkovski

2.
Theory
- WebSocket is a protocol providing full-duplex
communications over a single TCP
connection.
- Standardized by IETF as RFC 6455
- Designed to be implemented in web browsers
and web servers
- HTTP Upgrade request for initiating
connection
* Contents from Wikipedia: http://en.wikipedia.org/wiki/Web_sockets
GET /mychat HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: x3JJHMbDL1EzLkh9GBhXDw==
Sec-WebSocket-Protocol: chat
Sec-WebSocket-Version: 13
Origin: http://example.com
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept:
HSmrc0sMlYUkAGmm5OPpG2HaGWk=
Sec-WebSocket-Protocol: chat
Netcetera | 2

3.
Sample application
https://github.com/hsilomedus/web-sockets-samples
Netcetera | 3

4.
public static void main(String[] args)
JavaWebSocket (web-socket-samples/javawebsockets)
public class Main extends WebSocketServer {
public Main() {
super(new InetSocketAddress(8887));
}
@Override
public void onOpen(WebSocket conn,
ClientHandshake handshake) {
//Handle new connection here
conn.send(“{”connected”: true}”);
}
@Override
public void onMessage(WebSocket conn,
String message) {
//Handle client received message here
}
* https://github.com/TooTallNate/Java-WebSocket
@Override
public void onClose(WebSocket conn, int code,
String reason, boolean remote) {
//Handle closing connection here
}
@Override
public void onError(WebSocket conn,
Exception exc) {
//Handle error during transport here
}
public static void main(String[] args) {
Main server = new Main();
server.start();
}
}
Netcetera | 4

5.
Client
JavaScript WebSocket API
var socket = new WebSocket(“ws://localhost:8887”);
socket.onopen = function() {
//event handler when the connection has been established
socket.send(nickname);
};
socket.onmessage = function(message) {
//event handler when data has been received from the server
alert(message.data);
};
socket.onclose = function() {
//event handler when the socket has been properly closed
}
socket.onerror = function() {
//event handler when an error has occurred during communication
}
Netcetera | 5

6.
Java EE 7: JSR 356 + Java7
Tomcat (>7.0.43) (web-socket-samples/eesockets)
@ServerEndpoint(“/chat”)
public class EESocketChatEndpoint {
@OnOpen
public void onOpen(Session session) {
//Handle new connection here
session.getBasicRemote()
.sendText(“{”connected”: true}”);
}
@OnMessage
public void onMessage(String message) {
//Handle client received message here
}
@OnClose
public void onClose(Session session,
CloseReason reason) {
//Handle closing connection here
}
@OnError
public void onError(Session session,
Throwable throwable) {
//Handle error during transport here
}
}
* JSR 356, Java API for WebSocket: http://www.oracle.com/technetwork/articles/java/jsr356-1937161.html (javax.websocket.*)
Netcetera | 6

7.
Client
Pretty much the same JavaScript WebSocket API
var socket = new WebSocket(”ws://” + document.domain + “:8080/eesockets/chat”);
socket.onopen = function() {
//event handler when the connection has been established
socket.send(nickname);
};
socket.onmessage = function(message) {
//event handler when data has been received from the server
alert(message.data);
};
socket.onclose = function() {
//event handler when the socket has been properly closed
}
socket.onerror = function() {
//event handler when an error has occurred during communication
}
Netcetera | 7

8.
Spring4
Static dispatcher servlet config
public class DispatcherServletInitializer extends
AbstractAnnotationConfigDispatcherServletInitializer{
@Override
protected Class<?>[] getRootConfigClasses() { return null; }
@Override
protected Class<?>[] getServletConfigClasses() {
return new Class<?>[] {WebConfig.class};
}
@Override
protected String[] getServletMappings() { return new String[]{“/”}; }
@Override
protected void customizeRegistration(Dynamic registration) {
registration.setInitParameter(“dispatchOptionsRequest”, “true”);
}
}
Netcetera | 8

9.
Spring4
Static context config
@Configuration
@EnableWebMvc
@EnableWebSocket
@ComponentScan(basePackages={“mk.hsilomedus.springsockets.service”})
public class WebConfig extends WebMvcConfigurerAdapter implements WebSocketConfigurer {
public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
registry.addHandler(chatWenSocketHandler(), “/chat”).withSockJS();
}
@Bean
public WebSocketHandler chatWebSocketHandler() {
return new PerConnectionWebSocketHandler(ChatWebSocketHandler.class);
}
@Override
public void configureDefaultServletHandling(DefaultServerHandlerConfigurer configurer) {
configurer.enable();
}
Netcetera | 9
}

10.
Spring4
WebSocketHandler (web-socket-samples/springsockets)
public class ChatWebSocketHandler extends
TextWebSocketHandler {
@Override
public void afterConnectionEstablished(
WebSocketSession session) {
//Handle new connection here
session.sendMessage(
“{”connected”: true}”);
}
@Override
public void handleTextMessage(
WebSocketSession session,
TextMessage message) {
//Handle message.getPayload() here
}
* http://blog.gopivotal.com/products/websocket-architecture-in-spring-4-0
@Override
public void afterConnectionClosed(
WebSocketSession session,
CloseStatus status) {
//Handle closing connection here
}
@Override
public void handleTransportError(
WebSocketSession session,
Throwable exception) {
//Handle error during transport here
}
}
Netcetera | 10

11.
Client
SockJS
//I can now fallback to longpoll and do IE9!!!
var socket = new SockJS(”http://” + document.domain + “:8080/springsockets/chat”);
socket.onopen = function() {
//event handler when the connection has been established
socket.send(nickname);
};
socket.onmessage = function(message) {
//event handler when data has been received from the server
alert(message.data);
};
socket.onclose = function() {
//event handler when the socket has been properly closed
}
socket.onerror = function() {
//event handler when an error has occurred during communication
}
Netcetera | 11

12.
socket.close();
Thanks for your attention
- The whole source code is available on github:
https://github.com/hsilomedus/web-sockets-samples
- /javawebsockets – with the JavaWebSocket library
- /eesockets – with Tomcat 7.0.47
- /springsockets – with Spring4 RC2 and Tomcat 7.0.47
- All three are eclipse projects running on Java7
- Questions?
- https://twitter.com/hsilomedus, http://hsilomedus.me/
Netcetera | 12