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WebSocket & JSON Java APIs Hackday

By Somay Nakhal @SomayNakhal

David Illsley @davidillsley

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Hackday ?

Adapt A JSR programme Explore new APIs JSR 353 JSON Processing API JSR 356 WebSockets API Provide feedback

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WebSocket and Java

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

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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

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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

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Browser Support

caniuse.com

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WebSocket API (JavaScript)

var websocket = new WebSocket("ws://www.host.com/path"); 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");

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JSR 356 Java API for WebSocket

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Client and Server WebSocket protocol APIs in Java Integration with Java EE Web container Reference Implementation: – http://java.net/projects/tyrus – Bundled in latest Glassfish 4 builds

JSR 356 Java API for WebSocket

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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

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Annotations

@WebSocketEndpoint– Class level annotation for websocket server endpoint

@WebSocketClient – Class level annotation for websocket client endpoint

@WebSocketOpen – Method level annotation signifies a method to be called whenever a new

client connects to this endpoint

@WebSocketClose– Method level annotation signifies a method to be called whenever a new

client is about to disconnects from this endpoint

@WebSocketMessage– Method level annotation signifies a method to be called whenever an

incoming message is received

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Some Code!

@WebSocketEndpoint("/hello-world")public class HelloWorld {

@WebSocketMessagepublic String sayHello(String name) {

return "Hello " + name;}

}

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More Code!

@WebSocketEndpoint("/hello-world")public class HelloWorld {

private Set<Session> peers = Collections.synchronizedSet(…)

@WebSocketOpenpublic void onOpen (Session peer) {

peers.add(peer);}

private void sendMessageToPeer(String message, Session peer) { peer.getRemote().sendString(s);

}

}

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JSON and Java

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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

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tumbleweed...

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Not Quite

"The Software shall be used for Good, not Evil."

From: http://www.json.org/license.html

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And many more...

• org.json.me.

• Jackson JSON Processor.

• Json-lib.

• JSON Tools.

• Stringtree.

• SOJO.

• Jettison.

• json-taglib.

• XStream.

• Flexjson.

• JON tools.

• Argo.

• jsonij.

• fastjson.

• mjson.

• jjson.

• json-simple.

• json-io.

• JsonMarshaller.

• google-gson.

• Json-smart.

• FOSS Nova JSON.

(list from json.org)

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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."

http://jcp.org/en/jsr/detail?id=353

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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."

http://jcp.org/en/jsr/detail?id=353

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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

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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", "212 555-1234") .writeEnd() .writeStartObject() .write("type", "fax") .write("number", "646 555-4567") .writeEnd() .writeEnd() .writeEnd(); generator.close();

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Produces

{ "firstName": "John", "lastName": "Smith", "age": 25, "address" : { "streetAddress": "21 2nd Street", "city": "New York", "state": "NY", "postalCode": "10021" }, "phoneNumber": [ {"type": "home", "number": "212 555-1234"}, {"type": "fax", "number": "646 555-4567"} ] }

(JavaDoc - JsonGenerator) http://bit.ly/11CwMde

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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", "212 555-1234")) .add(Json.createObjectBuilder() .add("type", "fax") .add("number", "646 555-4567"))) .build();

// or from a stream..

JsonObject value2 = Json.createReader(inputStream).readObject();

(JavaDoc - JsonObject) bit.ly/11CwMde

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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");

}

}

}

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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/VzGWEr

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JSON Hacks/Workshop

Latest version of the library not in Glassfish yet, so a small standalone maven project

https://github.com/davidillsley/json-workshop

Includes tests for some uncompleted code operating on stored JSON.. see the README for more.

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