REST, dojo, Comet

Carol McDonald, Java Architect

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About the Speaker

• Carol cDonald: > Java Architect at Sun Microsystems> Before Sun, worked on software development of:

●Application to manage car Loans for Toyota (>10 million loans)

●Pharmaceutical Intranet apps (Roche Switzerland) ●Telecom Network Mgmt (Digital France) ●X.400 Email Server (IBM Germany)

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Agenda

• REST and JAX-RS• Dojo • Comet

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Example RESTful Catalog

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RESTful Slideshow using JAX-RS and comet

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REST and JAX-RSREST and JAX-RS

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REpresentational State Transfer

Client State1 Client State2

REST Web ServiceGet http://www.parts-depot.com/parts

Response XML data =REpresentational State

Transfer

● The URL identifies the resource● GET the page from the server● html page is transferred to the browser

– REpresentational State transfer● You click on a hyperlink in page (hypermedia), the process is repeated● The page (application state) is stored on the client (browser)

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REST Tenets

• Resources (nouns)> Identified by a URI, For example:

●http://petstore/catalog/items/

• Methods (verbs) to manipulate the nouns> Small fixed set:

●GET=Read, PUT=Update, POST=Create, Delete

• Representation of the Resource > data and state transferred between client and server> XML, JSON...

• Use verbs to exchange application state and representation

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HTTP ExampleRequestGET /catalog/items HTTP/1.1Host: petstore.comAccept: application/xml

ResponseHTTP/1.1 200 OKDate: Tue, 08 May 2007 16:41:58 GMTServer: Apache/1.3.6Content-Type: application/xml; charset=UTF-8

<?xml version="1.0"?><items xmlns="…"> <item>…</item> …</items>

Method Resource

Representation

Statetransfer

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JAX-RS: Clear mapping to REST concepts

• High level, Declarative> Uses @ annotation in POJOs

• Resources: what are the URIs?@Path("/items/{id}")

• Methods: what are the HTTP methods?@GETpublic XXX find()

• Representations: what are the formats?@Consumes("application/xml")@Produces("application/json")

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Example RESTful Catalog

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Example RESTful Catalog Service

CatalogDatabase

TestClient

dojoClient

Web container(GlassFish™)

+REST API

Browser(Firefox)

Resource Classes

Convertor Classes

Entity Classes

HTTP

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URIs and Methods:

● /items– GET - list all items– POST – add item to catalog

/items/{id}> GET - get an item representation> PUT - update an item> DELETE – remove an item

Item Catalog Example

http://www.infoq.com/articles/rest-introduction

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POJO

@Path("/items/")public class ItemsResource {

@Produces("application/json") @GET public ItemsConverter get() { ... }

...}

responds to the URI http://host/catalog/items/

responds with JSON

responds to HTTP GET method

resource

Representation

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Methods @Path(“/items”)class ItemsResource { @GET Items get() { ... } @POST Response create(Item) { ... }}

class ItemResource { @GET Item get(...) { ... } @PUT void update(...) { ... } @DELETE void delete(...) { ... }} Java method name is not significant

The @HTTP method is the method

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RESTful Catalog

DB

Registration Application

JAX-RS class

Dojo clientJAXB class

Entity Class

ItemsConverter

Item

ItemsResource

● Dojo client, JAX-RS, JAXB, JPA

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Entity Classes• Use JPA to map/retrieve data from the database as

entities• expose entities as RESTful resources

> entity = resource identified by URL

public class Item {

int id; String name; String descr; String url;

}

@Entity

@Id

ItemID NAME DESC URL

http://host/catalog/items/123

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Converter Classes

• JAXB to convert the domain objects (JPA entities) into XML and/or JSON.

DB

JAX-RS class

Dojo clientJAXB class

Entity Class

ItemsConverter

Item

ItemsResource

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ItemConverter JAXB annotated @XmlRootElement(name = "item")public class ItemConverter { private Item entity; private URI uri;

@XmlAttribute public URI getUri() { return uri; } @XmlElement public Long getId() { return (expandLevel > 0) ? entity.getId() : null; } ... }

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XML

<item uri="http://localhost/Web/resources/items/1/"> <description> black cat is nice</description> <id>1</id> <imagethumburl>/images/anth.jpg</imagethumburl> <name>not Friendly Cat</name> <price>307.10</price> <productid>feline01</productid> </item>

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JSON

{ "@uri":"http://host/catalog/resources/items/1/", "name":"Friendly Cat", "description":"This black and white colored cat is super friendly.", "id":"1", "imageurl":"http://localhost:8080/CatalogService/images/anthony.jpg" }

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ItemsConverter JAXB annotated @XmlRootElement(name = "items")public class ItemsConverter { private Collection<ItemConverter> items; private URI uri;

@XmlAttribute public URI getUri() { return uri; } @XmlElement public Collection<ItemConverter> getItem() { ... return items; }}

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XML<?xml version="1.0" encoding="UTF-8"?> <items uri="http://localhost/Web/resources/items/"> <item uri="http://localhost/Web/resources/items/1/"> <description> black cat is nice</description> <id>1</id> <imagethumburl>/images/anth.jpg</imagethumburl> <name>not Friendly Cat</name> <price>307.10</price> <productid>feline01</productid> </item> <item . . . </item> </items>

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JSON

{ "@uri":"http://host/catalog/resources/items/", "item":[ {"@uri":"http://host/catalog/resources/items/1/", "name":"Friendly Cat", "description":"This black and white colored cat is super friendly.", "id":"1", "imageurl":"http://localhost:8080/CatalogService/images/anthony.jpg"}, {"@uri":"http://host/catalog/resources/items/2/", "name":"Fluffy Cat", "description":"A great pet for a hair stylist! "id":"2", "imageurl":"http://localhost:8080/CatalogService/images/bailey.jpg"} ] }

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Resource Classes> Items Resource retrieves updates a collection of Item entities> /items – URI for a list of Items> Item resource retrieves or updates one Item entity> /item/1 – URI for item 1

DB

JAX-RS class

Dojo clientJAXB class

Entity Class

ItemsConverter

Item

ItemsResource

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Get Items @Path("/items/")public class ItemsResource { @Context protected UriInfo uriInfo; @GET @Produces("application/json") public ItemsConverter get(){ return new ItemsConverter( getEntities(), uriInfo.getAbsolutePath()); }

Performs JPAQuery, returns listof entities

JAXB class

responds with JSON

responds to the URI http://host/catalog/items/

responds to HTTP GET

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Get Item@Path("/items/")public class ItemsResource {

@Path("{id}/") public ItemResource getItemResource(@PathParam("id") Long id) { return new ItemResource(id, context); }}

public class ItemResource { @GET @Produces("application/json") public ItemConverter get() { return new ItemConverter(getEntity(), context.getAbsolutePath(), expandLevel); }

JAXB class

http://host/catalog/items/123

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Dojo Client SideDojo Client SideJavaScript LibraryJavaScript Library

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What is the Dojo Toolkit?

• Open Source set of JavaScript libraries• Simplifies javascript • support

> SitePen, IBM, Sun, JotSpot, Renkoo, AOL TurboAjax, OpenLaszlo, Nexaweb, Bea Systems

• http://dojotoolkit.com/• Server side technology independent,

source: dojotoolkit.org

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Dojo 3 main parts: Dojo

> Browser normalization, package loading, DOM access and manipulation, Firebug Lite debugging, events, data access, Drag and drop, Asynchronous remote calls, JSON encoding/decoding

dijit > Interface widgets, Advanced UI

controls,Template driven

dojoX> Inventive innovative: graphics, offline, widgets like

grid spreadsheat,

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LoadingLoading ddojo ojo

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Use Dojo from Content Distribution Network :

•download nothing and simply pull Dojo from a CDN near you:

AOL: <SCRIPT TYPE="text/javascript" SRC="http://o.aolcdn.com/dojo/1.2.0/dojo/dojo.xd.js"></SCRIPT>

Google: <SCRIPT TYPE="text/javascript" SRC=”http://ajax.googleapis.com/ajax/libs/dojo/1.2.0/dojo/dojo.xd.js"></SCRIPT>

script element is responsible for loading the base Dojo script

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Use Dojo from your Web Server :

• Download from http://dojotoolkit.org/downloads• Unzip the file, rename top folder to src <script type="text/javascript" djConfig="parseOnLoad: true" src="js/dojo/dojo.js" > </script>

script element is responsible for loading the base Dojo script

The package system handles the loading of all other dependencies and modules once dojo.js has been loaded into the page

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Use bundled Dojo with Netbeans project:

• Create a Netbeans project. Add Netbeans bundled dojo library to project:

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Or Use downloaded Dojo with Netbeans project:(if you want a different version)

• Download from http://dojotoolkit.org/downloads• Unzip the file, rename top folder to js• Create a Netbeans project. Copy js folder into

the web folder of your Netbeans project :

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Run File themeTester.html

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Try out dojo dijit widgets

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Setting up dojo javascript in the page

<head> <style type="text/css"> @import "js/dojo/resources/dojo.css";"; </style> <script type="text/javascript" src="js/dojo/dojo.js" djConfig="parseOnLoad: true" isDebug: true > </script></head>

Use firebug lite for debugging

Load the dojo style sheet

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Logging console.log("log button clicked");console.debug("debug button clicked");console.info("info button clicked");console.warn("warn button clicked");console.error("error button clicked");

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Dijit = Dijit = ddojo Widgetojo Widget

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dijit is a UI widget system layered on top of dojo

The dojo Widget Library

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What is a dojo Widget?

• Is a UI element such as a button, text box, scroll bar, calendar, tree etc> Easy to use> Event handlers can be registered on widget> handle browser incompatibilities

• HTML+CSS bound by JavaScript

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Creating a Button Widget<head> <style type="text/css"> @import "js/dijit/themes/tundra/tundra.css"; @import "js/dojo/resources/dojo.css"; </style> <script type="text/javascript" djConfig="parseOnLoad: true" src="js/dojo/dojo.js" ></script> <script type="text/javascript"> dojo.require("dijit.form.Button"); </script></head><body class="tundra">

<button dojoType="dijit.form.Button" onclick="call_function"> Log Button</button>

Load the Dijit style sheet

Class of widgets matches style Load form button module

For declarative widgets

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Form Widgets• CheckBox, RadioButton,ComboBox,

CurrencyTextBox, DateTextBox, NumberTextBox, Slider, ValidationTextBox, Textarea

• Attributes: disabled: Boolean• Methods:

> focus Set the focus on this widget > getValue get the value of the widget. > setValue set the value of the widget. > reset resets the widget to it's initial value > undo restore the value to the last value

• Extension Points: onChange: callback function

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Example dijit.form.DateTextBox

<script>dojo.require("dijit.form.DateTextBox");

</script><body><input type="text" name="date1"

value="2005-12-30"dojoType="dijit.form.DateTextBox"required="true" />

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Dijit Layout

• Accordion Container,Content Pane, Layout Container, Split Container, Stack Container, Tab Container

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Dijit Command Control

• Button, ComboButton, DropDownButton, Menu, Toolbar

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Dojo Event systemDojo Event system

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dojo.event.connect(srcObj,"srcFunc", targetFunc);

function myFunction() { alert("dojo.connect handler");

}

var link = dojo.byId("mylink");

dojo.event.connect(link, "onclick", myFunction);

<a href="#" id="mylink">Click Me</a>

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XMLHttpRequest (XHR):XMLHttpRequest (XHR):dojo.xhrDelete(), dojo.xhrDelete(), dojo.xhrGet(), dojo.xhrGet(), dojo.xhrPost(),  dojo.xhrPost(),  dojo.xhrPut()dojo.xhrPut()

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Traditional Web AJAX

within a browser, there is AJAX engine

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RESTful Pet Catalog Web Service

A d d r e s s ab le

R e s o u r c es

W e b C o n t a in e r

Server

Client

http://petstore/catalog/resources/items/

HTTP GET

{"url":"http://store/catalog/item1",{"url":"http://store/catalog/item2"}

Response JSON slide urls

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Dojo Client

• Use dojo.xhrGet to make HTTP method call to catalog service to get JSON items data:

{"items": {"@uri":"http://host/catalog/resources/items/", "item":[ {"@uri":"http://host/catalog/resources/items/1/", "name":"Friendly Cat", "description":"This black and white colored cat is super friendly.", "id":"1", "imageurl":"http://localhost:8080/CatalogService/images/anthony.jpg"}, {"@uri":"http://host/catalog/resources/items/2/", "name":"Fluffy Cat", "description":"A great pet for a hair stylist! "id":"2", "imageurl":"http://localhost:8080/CatalogService/images/bailey.jpg"} ] } }

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Getting Items from the RESTful Service

loadSlides: function (){ var targetURL = "resources/items/"; dojo.xhrGet({ url: targetURL, handleAs: "json", load: room.handleResponse, error: room.handleError }); },

handleResponse: function (responseObject, ioArgs){ if(!responseObject.item ){ return ; } ...

},

call url

Callback function

Response Data format

On error function

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Example RESTful Catalog

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Dojo client index.html

<button dojoType="dijit.form.Button" onclick="next"> Next</button>

<div id="grid" dojoType="dojox.Grid" model="model" structure="layout" autoWidth="true" >

http://weblogs.java.net/blog/caroljmcdonald/archive/2008/08/a_restful_pet_c.html

Grid widget model=data to display in grid

structure=layout for Grid

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Dojo client.js formatImage = function(value) { if (!value) return '&nbsp;'; return "<img src='" + value + "'/>"; };// Data Grid layout// A grid view is a group of columnsvar view1 = { cells: [ [ {name: 'Name', field: "name"}, {name: 'Description', field: "description"}, {name: 'Photo',field: "imagethumburl",

formatter: formatImage, }, {name: 'Price',field: "price"} ] ]};// a grid layout is an array of views.var layout = [ view1 ];// the model= collection of objects to be displayed in the gridmodel = new dojox.grid.data.Objects(null,null);

model=data to display in grid

layout for Grid

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Dojo client.js // make request to the items web servicefunction loadTable(page){ start = page * batchSize; var targetURL = "resources/items/?start="+

encodeURIComponent(start); dojo.xhrGet({ url: targetURL, handleAs: "json", load: handleResponse, error: handleError });}// Process the response from the items web servicefunction handleResponse(responseObject, ioArgs){ // set the model object with the returned items list model.setData(responseObject.items.item); }function next() { page =page + 1; loadTable(page);}

Performs HTTPGET on url catalog/items

Callback puts response data in dojo model

for grid table

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COMETCOMET

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Comet:

Server

Client 1 Client 2

the server pushes data to the client over a long-lived HTTP connection

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Ajax Push and HTTP keep-alive

Comet:

• server pushes data to the client over a previously opened connection

HTTP/1.1 Keep-Alive or Persistent Connection:

• keeps connection open until an explicit 'close connection' message or timeout Long Poll: Send a request to the server,

request waits for an event, then response sent

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Ajax PushHTTP example

GET /slideshow/resources/slides

Accept: */*

Connection: keep-alive

Host: localhost:8080

Handshake

HTTP/1.1 200 OKContent-Type: application/json-comment-filteredServer: GlassFish/v3

/*[{"id":"0","minimumVersion":0.9,"supportedConnectionTypes":["long-polling","callback-polling"],"successful":true,"advice":{"reconnect":"retry","interval":0},"channel":"/meta/handshake","clientId":"3b37f0aae53ab2f1","ext":{"json-comment-filtered":true},"version":1.0}]*/

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Blocking http request =server catastrophe

GET /updates HTTP/1.1Connection: keep-alive

GET /updates HTTP/1.1Connection: keep-alive

GET /updates HTTP/1.1Connection: keep-alive

GET /updates HTTP/1.1Connection: keep-alive

GET /updates HTTP/1.1Connection: keep-alive

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GlassFish Grizzly CometNIO:

• non-blocking sockets

ARP Asynchronous Request Processing:

• Doesn't block a thread per http request

• availability of threads gives scalability

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Introduction to Grizzly Comet

• Grizzly Comet is a framework that ship with GlassFish v1|2|3, and can also be embedded into any application using the Grizzly Embed interface (no fish involved).

• The Grizzly Comet Framework includes a set of components that can be used for building Comet based application:> Grizzly Comet, Continuation, Grizzlet, Messages Bus,

Bayeux support

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Server-side Ajax Push: Who supports whatThe asynchronicity matrix.

XWebLogic

Container Asynchronous IO

Suspendible Request/Response

Delivery Guarantee

Jetty XTomcat X XGlassFish X X XResin X

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The Bayeux Protocol

• http://svn.xantus.org/shortbus/trunk/bayeux/bayeux.html

• Bayeux is a JSON-based protocol for clients to register interest in events and for servers to deliver them in a more timely fashion than Ajax-based polling allows.

• With Bayeux, you only needs to write the client.

• The goals of the Bayeux spec so far have been to:> make event delivery fast> keep it simple> provide extension points in the protocol

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Bayeux

HTTP Publish Subscribe

protocol for routing JSON-encoded events between clients and servers in a publish-subscribe model

Grizzly provides an implementation of Bayeux

Just configure Glassfishdomain.xmland Web App web.xml

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Bayeux

Multiple Channels

Http

Comet and Reverse Ajax

Cometd clients

JSON Messages are published on specified channels

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Bayeux/CometdJSON Publish/Subscribe

• JSON Messages are published on specified channels

• Channel operations: connect, subscribe, unsubscribe, etc.

• Multiple transports: polling, long-polling, iframe, flash

• Server-side just event bus for client side

[

{

"channel": "/some/name",

"clientId": "83js73jsh29sjd92",

"data": { "myapp" : "specific data", value: 100 } }

]

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Enable Comet in GlassFish V2 Admin Console

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Configure Cometd • Enabling Bayeux in GlassFish

> web.xml<servlet> <servlet-name>Grizzly Cometd Servlet</servlet-name> <servlet-class> com.sun.grizzly.cometd.servlet.CometdServlet</servlet-class> </servlet><servlet-mapping> <servlet-name>Grizzly Cometd Servlet</servlet-name> <url-pattern>/cometd/*</url-pattern></servlet-mapping>

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Cometd

HTTP Requests

dojox.cometd●Dojo-based JavaScript client●Implementation of Bayeux Protocol

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RESTful Web Services and Comethttp://developers.sun.com/appserver/reference/techart/cometslideshow.html

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RESTful Slideshow Web Service

A d d r e s s ab le

R e s o u r c es

W e b C o n t a in e r

Server

Client

http://host/slideshow/resources/slides/

HTTP GET

{"url":"http://host/slideshow/image1.jpg",{"url":"http://host/slideshow/image2.jpg"}

Response JSON slide urls

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Cometd Step1 : Initialize

dojo.require("dojox.cometd");

//Initialize a connection to the given Comet server: the GlassFish Grizzly Bayeux servlet

dojox.cometd.init("serverURL");

Comet Server

Client 1Client 2

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Cometd Step 2: Subscribe

Client 1Client 2

dojox.cometd.subscribe(“topic”, "object", "callbackFunction");

• Subscribes the client to the topic channel

• Any time a message is sent to the topic channel

• the object's callback will be invoked

Comet Server

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Cometd Step 3: Publish

Comet Server

Next sl ide url

dojox.cometd.publish("topic", {slide: url});

a client publishes the next slide url to the topic channel

JSON message

client 1

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Cometd Step 4: Update Clients: CallBack Comet Server

Client 2 Client 3

callBackFunction(slideUrl){ slide.innerHTML ="<img src='" + slideUrl + "'/>"; ... }

●The callback function is called with the published message when a new message is received●This callback function updates the browser content

● html img tag with the slide url from the published message

Update Browser Update

Browser

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Summary

• REST architecture is gaining popularity> Simple, scalable and the infrastructure is already in

place

• JAX-RS (JSR-311) provides a high level declarative programming model> http://jersey.dev.java.net> NetBeans 6.1 , 6.5 has wizards to help

• Dojo makes javascript easier• Dojo cometd with Grizzly makes building comet

apps easy

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RESTful Web Services and Comethttp://developers.sun.com/appserver/reference/techart/cometslideshow.html

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RESTful Web Serviceshttp://netbeans.tv/screencasts/offset/7/

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Example RESTful Cataloghttp://weblogs.java.net/blog/caroljmcdonald/archive/2008/08/a_restful_pet_c.html

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For More Information• Web 2.0 & ajax

> http://developers.sun.com/ajax/• Dojo

> http://dojotoolkit.org/• JAX-RS Reference Implementation

> http://jersey.dev.java.net/

• Glassfish> https://glassfish.dev.java.net/> http://blogs.sun.com/theaquarium/

• Cometd> http://cometdproject.dojotoolkit.org/

• Carol's Blog> http://weblogs.java.net/blog/caroljmcdonald/

●

–

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Carol McDonald Java Architect

http://weblogs.java.net/blog/caroljmcdonald/