1
WebSocket & JSON Java APIs Hackday
By Somay Nakhal @SomayNakhal
David Illsley @davidillsley
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://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");
9
JSR 356 Java API for WebSocket
10
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
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
@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
13
Some Code!
@WebSocketEndpoint("/hello-world")public class HelloWorld {
@WebSocketMessagepublic String sayHello(String name) {
return "Hello " + name;}
}
14
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);
}
}
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
"The Software shall be used for Good, not Evil."
From: http://www.json.org/license.html
19
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)
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."
http://jcp.org/en/jsr/detail?id=353
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."
http://jcp.org/en/jsr/detail?id=353
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", "212 555-1234") .writeEnd() .writeStartObject() .write("type", "fax") .write("number", "646 555-4567") .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": "212 555-1234"}, {"type": "fax", "number": "646 555-4567"} ] }
(JavaDoc - JsonGenerator) http://bit.ly/11CwMde
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", "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
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/VzGWEr
28
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.
29
Top Related