introduction to the java api for websocket (jsr 356)

Introduction to the Java API for WebSocket (JSR 356)Reza RahmanJava EE/GlassFish EvangelistReza.Rahman@Oracle.com@reza_rahman

Agenda

WebSocket 101

JSR 356: Java API for WebSocket

WebSocket

HTTP/TCP based, bi-directional, full-duplex messaging Originally proposed as part of HTML5 IETF-defined Protocol: RFC 6455 W3C defined JavaScript API

Establish a connection

Client

Handshake Request

Handshake Response

Server

Handshake Request

GET /chat HTTP/1.1Host: server.example.comUpgrade: websocketConnection: UpgradeSec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==Origin: http://example.comSec-WebSocket-Protocol: chat, superchatSec-WebSocket-Version: 13

Handshake Response

HTTP/1.1 101 Switching ProtocolsUpgrade: websocketConnection: UpgradeSec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=Sec-WebSocket-Protocol: chat

Establishing a Connection

ServerClient

Handshake Request

Handshake Response

Connected !

WebSocket Lifecycle

ServerClient

Connected !

open open

message

messagemessage

Disconnected

Browser Support

Java API for WebSocket

Create WebSocket Endpoints– Interface-driven (Endpoint)

– Annotation-driven (@ServerEndpoint)

Client and server APIs Part of Java EE 7 SPI for extensions and data frames

Basic API Tour

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. } } }); }}

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) { ... } }}

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);

Sending the Message

Whole string *RemoteEndpoint.Basic

sendText(String message)

Binary data *RemoteEndpoint.Basic

sendBinary(ByteBuffer message)

String fragmentsRemoteEndpoint.Basic

sendText(String part, boolean last)

Binary data fragmentsRemoteEndpoint.Basic

sendBinary(ByteBuffer part, boolean last)

Blocking stream of text

RemoteEndpoint.Basic

Writer getSendWriter())

Blocking stream of binary data

RemoteEndpoint.Basic

OutputStream getSendStream()

Custom objectRemoteEndpoint.Basic

sendObject(Object customObject)

* Additional flavors: by completion, by future

Receiving the Message

Whole stringMessageHandler.Whole<String>

onMessage(String message)

Binary dataMessageHandler.Whole<ByteBuffer>

onMessage(ByteBuffer message)

String fragmentsMessageHandler.Partial<String>

onMessage(String part, boolean last)

Binary data fragments

MessageHandler.Partial<ByteBuffer>

onMessage(ByteBuffer part, boolean last)

Blocking streamof text

MessageHandler.Whole<Reader>

onMessage(Reader r)

Blocking streamof binary data

MessageHandler.Whole<InputSteam>

onMessage(InputStream r)

Custom objectof type T

MessageHandler.Whole<T>

onMessage(T customObject)

POJO + Annotations

Hello World Annotations

@ServerEndpoint("/hello")public class HelloBean {

@OnMessage public String sayHello(String name) { return "Hello " + name; }}

WebSocket Annotations

Annotation Level Purpose

@ServerEndpoint ClassTurns a POJO into a WebSocket Server Endpoint

@ClientEndpoint ClassTurns 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

@PathParamMethod

ParameterFlags a matched path segment of a URI-template

@OnError Method Intercepts errors during a conversation

@ServerEndpoint Attributes

valueRelative URI or URI template

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

configurator Custom configuration

decoders List of message decoder classnames

encoders List of message encoder classnames

subprotocols List of the names of the supported subprotocols

Custom Payloads

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

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(); }}

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) { ... }}

Chat Sample

@Singleton @ServerEndpoint("/chat")

public class ChatServer {

private Set<Session> peers = new HashSet();

@OnOpen public void onOpen(Session peer) { peers.add(peer); }

@OnClose public void onClose(Session peer) { peers.remove(peer); } ...

Chat Sample (Continued)

@OnMessage

public void message(String message) {

for (Session peer : peers) { peer.getBasicRemote().sendText(message); } }}

URI Template Matching

@ServerEndpoint("/orders/{order-id}")public class MyEndpoint { @OnMessage public void processOrder( @PathParam("order-id") String orderId) { ... }}

@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

Java WebSocket Demo

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

https://github.com/m-reza-rahman/whiteboard

Try it Out!

http://dlc.sun.com.edgesuite.net/glassfish/4.0.1/promoted/

Java WebSocket Implementations

Tomcat

GlassFish

Summary

Bi-directional full-duplex communication on the web– Chat, online multiplayer games, collaboration, real time monitoring

Java API for WebSocket standardized as part of Java EE 7– Interface-driven– Annotation-driven

Client and server APIs Supported by major server-side Java platforms

Learning More

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

– GlassFish: http://glassfish.org

Dig Deeper– Java EE Tutorial:

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

– Java EE 7 Hands-on-Lab: https://glassfish.java.net/hol/

– Cargo Tracker Java EE Blue Prints Project: https://java.net/projects/cargotracker/

introduction to the java api for websocket (jsr 356)

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