Building Java HTML5/WebSocket Applications with JSR 356

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Building Java
HTML5/WebSocket
Applications with JSR 356
Reza Rahman
Java EE/GlassFish Evangelist
Reza.Rahman@Oracle.com
@reza_rahman

Program Agenda

 WebSocket Primer

 JSR 356: Java API for WebSocket
 Demo

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Interactive Web Sites
 HTTP is half-duplex
 Flavors of Server Push
– Polling
– Long Polling

– Comet/Ajax

 Complex, Inefficient, Wasteful

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WebSocket to the Rescue
 TCP based, bi-directional, full-duplex messaging
 Originally proposed as part of HTML5
 IETF-defined Protocol: RFC 6455
 W3C defined JavaScript API

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What’s the basic idea ?
 Establish connection (Single TCP connection)
 Send messages in both direction (Bi-directional)
 Send message independent of each other (Full Duplex)
 End connection

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Establish a connection

Handshake Request

Client

Server
Handshake Response

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Handshake Request
GET /chat HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
Origin: http://example.com
Sec-WebSocket-Protocol: chat, superchat
Sec-WebSocket-Version: 13

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Handshake Response
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
Sec-WebSocket-Protocol: chat

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Establishing a Connection

Handshake Request

Client

Server
Handshake Response

Connected !

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WebSocket Lifecycle
Connected !

open

open

message

Client

message

error
message

Server
message

close

Disconnected

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WebSocket API
www.w3.org/TR/websockets/

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Java WebSocket Implementations
Java-WebSocket
Grizzly

WebSocket SDK

Apache Tomcat 7

Webbit

GlassFish

Atmosphere

Autobahn

websockets4j

WeberKnecht

GNU WebSocket4J

Jetty

Netty

JBoss

TorqueBox

Caucho Resin

SwaggerSocket

jWebSocket

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Kaazing WebSocket Gateway

jWamp


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Browser Support

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JSR 356: Java API for Web Socket
 Specification
– http://jcp.org/en/jsr/detail?id=356
– http://java.net/projects/websocket-spec
– Included in Java EE 7

 Reference Implementation
– http://java.net/projects/tyrus

– Bundled with Glassfish 4

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Java API for WebSocket Features
 Create WebSocket Endpoints
– Interface-driven (Endpoint)
– Annotation-driven (@ServerEndpoint)

 Client and server APIs
 SPI for extensions and data frames

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Basic API Tour

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Hello World Server
public class HelloServer extends Endpoint {
@Override
public void onOpen(Session session,
EndpointConfig configuration) {
session.addMessageHandler(
new MessageHandler.Whole<String>() {
public void onMessage(String name) {
try {
session.getBasicRemote().sendText(“Hello “ + name);
} catch (IOException ioe) {
// Handle failure.
}
}
});
}
}

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Hello World Client
public class HelloClient extends Endpoint {
@Override
public void onOpen(Session session,
EndpointConfig configuration) {
try {
session.getBasicRemote().sendText("Hello you!");
} catch (IOException ioe) {
. . .
}
}
}

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Client Server Configuration
ServerContainer serverContainer =
(ServerContainer) servletContext.getAttribute(
“javax.websocket.server.ServerContainer”);
ServerEndpointConfig serverConfiguration =
ServerEndpointConfig.Builder.create(
HelloServer.class, "/hello").build();
serverContainer.addEndpoint(serverConfiguration);
...
URI clientURI = new URI("ws://myserver.com/websockets/hello");
WebSocketContainer container =
ContainerProvider.getWebSocketContainer();
ClientEndpointConfig clientConfiguration =
ClientEndpointConfig.Builder.create().build();
container.connectToServer(HelloClient.class,
clientConfiguration, clientURI);

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Main API Classes: javax.websocket.*
 Endpoint: Intercepts WebSocket lifecycle events
 MessageHandler: Handles all incoming messages for an Endpoint
 RemoteEndpoint: Represents the ‘other end’ of this conversation
 Session: Represents the active conversation

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Public

Object Model
Message
Handler

Remote
Endpoint

Message
Handler

Remote
Endpoint

Client

Internet

Session

Message
Handler

Remote
Endpoint

Session

Client

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WebSocket
Endpoint

Session

Client

Sending the Message
Whole string *

RemoteEndpoint.Basic

sendText(String message)

Binary data *


sendBinary(ByteBuffer message)

String fragments


sendText(String part, boolean last)

Binary data fragments


sendBinary(ByteBuffer part, boolean last)

Blocking stream of text


Writer getSendWriter())

Blocking stream of binary
data

OutputStream getSendStream()

Custom object

sendObject(Object customObject)


* additional flavors: by completion, by future

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Receiving the Message
Whole string

MessageHandler.Whole<String>

onMessage(String message)

Binary data

MessageHandler.Whole<ByteBuffer>

onMessage(ByteBuffer message)

String fragments

MessageHandler.Partial<String>

onMessage(String part, boolean last)

Binary data fragments

MessageHandler.Partial<ByteBuffer>

onMessage(ByteBuffer part, boolean last)

Blocking stream of text

MessageHandler.Whole<Reader>

onMessage(Reader r)

Blocking stream of
binary data

MessageHandler.Whole<InputSteam> onMessage(InputStream r)

Custom object of type T

MessageHandler.Whole<T>

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onMessage(T customObject)

POJO + Annotations

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Hello World Annotations
@ServerEndpoint("/hello")
public class HelloBean {
@OnMessage
public String sayHello(String name) {
return “Hello “ + name;
}
}

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WebSocket Annotations
Annotation

Level

Purpose

@ServerEndpoint

class

Turns a POJO into a WebSocket Server Endpoint

@ClientEndpoint

class

Turns a POJO into a WebSocket Client Endpoint

@OnOpen

method

Intercepts WebSocket Open events

@OnClose

method

Intercepts WebSocket Close events

@OnMessage

method

Intercepts WebSocket Message events

method
Flags a matched path segment of a URI-template
parameter

@PathParam
@OnError

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method

Public

Intercepts errors during a conversation

@ServerEndpoint attributes

value

configurator

Custom configuration

decoders

list of message decoder classnames

encoders

list of message encoder classnames

subprotocols

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Relative URI or URI template
e.g. “/hello” or “/chat/{subscriber-level}”

list of the names of the supported subprotocols


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Custom Payloads
@ServerEndpoint(
value="/hello",
encoders={MyMessage.class},
decoders={MyMessage.class}
)
public class MyEndpoint {
. . .
}

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Custom Payloads – Text
public class MyMessage

implements Decoder.Text<MyMessage>, Encoder.Text<MyMessage> {
private JsonObject jsonObject;
public MyMessage decode(String s) {
jsonObject = new Json.createReader(

new StringReader(s)).readObject();
return this;
}
public boolean willDecode(String string) {
return true; // Only if can process the payload
}
public String encode(MyMessage myMessage) {
return myMessage.jsonObject.toString();
}
}

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Custom Payloads – Binary
public class MyMessage
implements Decoder.Binary<MyMessage>, Encoder.Binary<MyMessage> {

public MyMessage decode(ByteBuffer bytes) {
. . .
return this;
}
public boolean willDecode(ByteBuffer bytes) {
. . .
return true; // Only if can process the payload
}
public ByteBuffer encode(MyMessage myMessage) {
. . .
}
}

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Chat Sample
@ServerEndpoint("/chat")
public class ChatBean {
Set<Session> peers = Collections.synchronizedSet(…);
@OnOpen
public void onOpen(Session peer) {
peers.add(peer);
}
@OnClose
public void onClose(Session peer) {
peers.remove(peer);
}
...

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Chat Sample (Continued)
. . .
@OnMessage
public void message(String message, Session client) {
for (Session peer : peers) {
peer.getRemote().sendObject(message);
}
}
}

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URI Template Matching
@ServerEndpoint(“/orders/{order-id}”)
public class MyEndpoint {
@OnMessage
public void processOrder(
@PathParam(“order-id”) String orderId) {
...
}
}

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@OnMessage Methods
 A parameter type that can be decoded in incoming message
– String, primitive, Reader, ByteBuffer, byte[], InputStream, or any type for

which there is a decoder
 An optional Session parameter
 Boolean partial flag
 0..n String parameters annotated with @PathParameter

 A return type that can be encoded in outgoing message
– String, primitive, Reader, ByteBuffer, byte[], InputStream, or any type for

which there is an encoder

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Java WebSocket Hello World Demo

https://github.com/m-reza-rahman/hello-websocket

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Try it Out!

http://download.java.net/glassfish/4.0/release/glassfish-4.0.zip

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Resources
 Specification
– JSR: jcp.org/en/jsr/detail?id=356
– Mailing Lists, JIRA, Archive: java.net/projects/websocket-spec

 Reference Implementation
– Tyrus: java.net/projects/tyrus

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Building Java HTML5/WebSocket Applications with JSR 356

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