using web services in your gadget/widget

Using Web Services in your Gadget

Alan Lewis – eBay Technical Evangelist

NGW024

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Hi

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I lost my voice earlier this morning

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:-(

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I have some cool stuff to show you though

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:-)

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So, I’ll give it a try

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Here goes…

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Huh? What’s this presentation about???

• Web Services

– You may have heard of them

– Yes, they are actually useful

– No, you don’t have to use SOAP

– Lots of services are out there for you to use (finally)

• Gadgets

– Or Widgets

– Or Plugins

– Or Panels

– Definition: “mini-applications that let you perform common tasks and provide you with fast access to information”

– Translation: They do cool stuff

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Why Should I Care?

• Gadgets are cool

• Web services offer lots of reusable data and functionality

• MIXing them up (nice plug) in your gadget saves you headaches

• Alternative to doing it this way – server side coding

– Need to scale your server to handle traffic from gadget

– Different skill set required

– Eww!!!

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So, what sorts of web services are out there?

• I’m so glad you asked… here is a totally random example:

eBay Web Services!!!

• Please permit me a short detour to summarize

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eBay Web Service Features

• Search

• Listing Items

• Transaction/Order Management

• My eBay

• eBay Stores

• Feedback Management

• Watch List

• Bidding (with signed agreement)

• In short, almost everything you can do on the site

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Different Flavors of eBay Web Services

• SOAP

• XML (HTTP POST) – Both support the same feature set (all calls)

– Calls go over HTTPS

• REST (HTTP GET)– supports GetSearchResults call

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Sample Call Request

XML API:

<?xml version="1.0" encoding="utf-8"?>

<GetSearchResultsRequest xmlns="urn:ebay:apis:eBLBaseComponents">

<RequesterCredentials>

<eBayAuthToken>ABC123</eBayAuthToken>

</RequesterCredentials>

<Query>iPod Nano</Query>

</GetSearchResultsRequest>  

REST API

http://rest.api.ebay.com/restapi?CallName=GetSearchResults&RequestToken=ABC123=&RequestUserId=alanlewis0&Query=iPod%20Nano&Schema=1

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Sample Call Response

XML API and REST API (same response)

<?xml version="1.0" encoding="utf-8"?>

<GetSearchResultsRequest xmlns="urn:ebay:apis:eBLBaseComponents">

…

<Item>

<ItemID>4036874357</ItemID>

…   

<SellingStatus>

<BidCount>31</BidCount>

<CurrentPrice currencyID="USD">80.0</CurrentPrice>

</SellingStatus>

<Site>US</Site>

<Title>Used Apple iPod Nano MP3 Player Good Condition</Title>

…

</Item>

…

</GetSearchResultsRequest>  

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And Now…

Demo

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Live.com

• Supports RSS feeds and Gadgets

• Gadgets are implemented in javascript + CSS

• Still alpha feel – emerging feature set and very buggy at times (especially with CSS support)

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Design Philosophy

• Gadgets call for a fresh design approach

• Sort of like code for mobile devices– Limited screen real-estate

– Limited functionality/APIs

• Except not– Still coding for the browser– multiple windows/tabs, cross-browser issues

– Asynchronous interaction, more bandwidth

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Challenge 1: Security Restrictions

• Calls can’t go across domains– If the gadget was served up from www.mydomain.com, can’t call api.ebay.com

• Live.com solution to this: proxy!– Supports XML data (except XHTML) and RSS feeds

– Currently only supports HTTP GET (contrary to docs – support for POST will be added in the future)

– Can’t proxy HTTPS yet, so only option for eBay is REST API

var r = Web.Network.createRequest( Web.Network.Type.XML,

searchQuery,

{proxy:"generic"},

eBaySearchCallback);

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Challenge 2: Namespaces

• IE javascript engine can’t handle XML data in default namespaces

• Solution: Use ugly RegEx hack to remove namespace:

var rootText = response.responseText;

var re = /xmlns="urn:ebay:apis:eBLBaseComponents"/g;

rootText = rootText.replace(re, "");

var responseWithoutNamespaces;

if (window.ActiveXObject) {

responseWithoutNamespaces = new ActiveXObject("Microsoft.XMLDOM");

responseWithoutNamespaces.async="false";

responseWithoutNamespaces.loadXML(rootText);

}

else {

responseWithoutNamespaces = document.implementation.createDocument("","",null);

responseWithoutNamespaces.loadXML(rootText);

}

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And now…

• ANNOUNCING:

• The gadget is open sourced

• Commercial software-friendly open source license: CDDL

• Yeah!

• http://searchgadget.codebase.ebay.com

• Lets go check it out…

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Now More Code

• Here is the code, in-depth

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Other Web Services

• Lots to choose from: www.programmableweb.com

• REST is very popular, but has limitations

• RSS feeds are web services too

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Building Commercial Apps

• One issue to keep in mind is many Web services out there force non-commercial use

• Shameless plug: that’s not the case with eBay Web services

• One way to make money with your Gadget is to use an affiliate program like eBay’s:http://developer.ebay.com/affiliates

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Other Gadget/Widget Platforms

• Vista Sidebar

– Bundled with Vista, but limited capabilities (thusfar)

• Yahoo! Widget Engine (Konfabulator)

– Multi-platform support, integration with Desktop still clumsy

• Apple Dashboard

– Best desktop integration, but only for OSX

• Google Desktop – (Sidebar)

– Information-rich widgets, but harder to build, bundled with a product IT departments hate

• Google Personalized Home Page

– Sorta like live.com – less functionality but better visibility

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Learn More Stuff

• More on eBay Web Services: http://developer.ebay.comIts totally free!

• eBay Developers Conference, baby!June 10-12, Mandalay Bay, Las Vegas

• Live.com eBay Gadget available in the Gallery:microsoftgadgets.com

• Open sourced at: http://searchgadget.codebase.ebay.com

• Sanaz Ahari’s presentation immediately following this one, in C/D