1 WebSocket & JSON Java APIs Hackday By Somay David

2 Hackday ?  Adapt A JSR programme  Explore new APIs  JSR 353 JSON Processing API  JSR 356 WebSockets API  Provide feedback

3 WebSocket and Java

4  Interactive web application  HTTP is half-duplex  Polling  Long Polling  Comet/Ajax  Complex, Inefficient, Wasteful

5 Enter WebSocket Protocol  TCP based, bi-directional, full-duplex messaging  Part of HTML5  IETF-defined Protocol: RFC 6455  W3C defined JavaScript API  Uses HTTP upgrade handshake  Supports HTTP proxies, filtering, authentication and intermediaries

6 How does it work?  Establish connection (Single TCP connection)  Send messages in both direction (Bi-directional)  Send messages independent of each other (Full Duplex)  End connection

7 Browser Support caniuse.com

8 WebSocket API (JavaScript) var websocket = new WebSocket("ws:// websocket.onopen = function(evt) { onOpen(evt) }; websocket.onclose = function(evt) { onClose(evt) }; websocket.onmessage = function(evt) { onMessage(evt) }; websocket.onerror = function(evt) { onError(evt) }; } function onMessage(evt) { alert( evt.data); } function onError(evt) { alert( evt.data); } websocket.send("client to server");

9 JSR 356 Java API for WebSocket

10  Client and Server WebSocket protocol APIs in Java  Integration with Java EE Web container  Reference Implementation:  –  – Bundled in latest Glassfish 4 builds JSR 356 Java API for WebSocket

11 Terminology  Endpoint: Client or server  Connection: Network connection between two endpoints  Peer: Other endpoint of the connection  Session: represents a sequence of websocket interactions between and end point and a peer

12 Annotations –Class level annotation for websocket server endpoint –Class level annotation for websocket client endpoint –Method level annotation signifies a method to be called whenever a new client connects to this endpoint –Method level annotation signifies a method to be called whenever a new client is about to disconnects from this endpoint –Method level annotation signifies a method to be called whenever an incoming message is received

13 Some public class HelloWorld public String sayHello(String name) { return "Hello " + name; }

14 More public class HelloWorld { private Set peers = public void onOpen (Session peer) { peers.add(peer); } private void sendMessageToPeer(String message, Session peer) { peer.getRemote().sendString(s); }

15 JSON and Java

16 In the beginning... There was XML... and the DOM... and SAX... Then, after much gnashing of teeth, there was JSON { "message" : "Hello World!" } More at json.org and wikipedia

17 tumbleweed...

18 Not Quite From: "The Software shall be used for Good, not Evil."

19 And many more... org.json.me. org.json.me Jackson JSON Processor. Jackson JSON Processor Json-lib. Json-lib JSON Tools. JSON Tools Stringtree. Stringtree SOJO. SOJO Jettison. Jettison json-taglib. json-taglib XStream. XStream Flexjson. Flexjson JON tools. JON tools Argo. Argo jsonij. jsonij fastjson. fastjson mjson. mjson jjson. jjson json-simple. json-simple json-io. json-io JsonMarshaller. JsonMarshaller google-gson. google-gson Json-smart. Json-smart FOSS Nova JSON. FOSS Nova JSON (list from json.org)

20 Fast-forward to December 2011 JSR 353: JavaTM API for JSON Processing "JSON(JavaScript Object Notation) is a lightweight data-interchange format. Many popular web services use JSON format for invoking and returning the data. Currently Java applications use different implementation libraries to produce/consume JSON from the web services. Hence, there is a need to standardize a Java API for JSON so that applications that use JSON need not bundle the implementation libraries but use the API. Applications will be smaller in size and portable."

21 Goals/Non Goals "The goal of this specification is to develop such APIs to: * Produce and consume JSON text in a streaming fashion(similar to StAX API for XML) * Build a Java object model for JSON text using API classes(similar to DOM API for XML) Non-goals of this specification include: * Binding of JSON text to Java objects and vice versa." "This JSR is targeted for Java SE 6 or higher and Java EE 7 or higher platforms."

22 Fast-forward to February 2013 Pretty much done Just finished the formal public review phase Looking for final feedback from JUGs... and to get the word out about what's coming

23 Some code... JsonGenerator generator = Json.createGenerator(System.out) // or generator = Json.createGenerator(servletResponse.getWriter()) generator.writeStartObject().write("firstName", "John").write("lastName", "Smith").write("age", 25).writeStartObject("address").write("streetAddress", "21 2nd Street").write("city", "New York").write("state", "NY").write("postalCode", "10021").writeEnd().writeStartArray("phoneNumber").writeStartObject().write("type", "home").write("number", " ").writeEnd().writeStartObject().write("type", "fax").write("number", " ").writeEnd().writeEnd().writeEnd(); generator.close();

24 Produces { "firstName": "John", "lastName": "Smith", "age": 25, "address" : { "streetAddress": "21 2nd Street", "city": "New York", "state": "NY", "postalCode": "10021" }, "phoneNumber": [ {"type": "home", "number": " "}, {"type": "fax", "number": " "} ] } (JavaDoc - JsonGenerator)

25 Or to build an object model... JsonObject value = Json.createObjectBuilder().add("firstName", "John").add("lastName", "Smith").add("age", 25).add("address", Json.createObjectBuilder().add("streetAddress", "21 2nd Street").add("city", "New York").add("state", "NY").add("postalCode", "10021")).add("phoneNumber", Json.createArrayBuilder().add(Json.createObjectBuilder().add("type", "home").add("number", " ")).add(Json.createObjectBuilder().add("type", "fax").add("number", " "))).build(); // or from a stream.. JsonObject value2 = Json.createReader(inputStream).readObject(); (JavaDoc - JsonObject) bit.ly/11CwMdebit.ly/11CwMde

26 And to read things from it... int age = value2.getIntValue("age", 18); JsonObject address = value2.getValue("address", JsonObject.class); String city = "London"; if(address != null){ city = address.getStringValue("city", "London"); } JsonArray phoneNumbers = value2.getValue("phoneNumber", JsonArray.class); if(phoneNumbers != null){ for(JsonValue val: value2){ if(val instanceof JsonObject){ JsonObject jo = (JsonObject)val; System.out.println(jo.getStringValue("number","Number Missing"); }

27 And a low-level event API Event event = parser.next(); // START_OBJECT event = parser.next(); // KEY_NAME event = parser.next(); // VALUE_STRING parser.getString(); // "John" (JavaDoc - JsonParser) bit.ly/VzGWErbit.ly/VzGWEr

28 JSON Hacks/Workshop Latest version of the library not in Glassfish yet, so a small standalone maven project Includes tests for some uncompleted code operating on stored JSON.. see the README for more.

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