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Web Services and Blackboard Bob Alcorn Blackboard, Inc.

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Presentation on theme: "Web Services and Blackboard Bob Alcorn Blackboard, Inc."— Presentation transcript:

1 Web Services and Blackboard Bob Alcorn Blackboard, Inc.

2 And now a word from our lawyers… Any statements in this presentation about future expectations, plans and prospects for Blackboard and other statements containing the words "believes," "anticipates," "plans," "expects," "will," and similar expressions, constitute forward-looking statements within the meaning of The Private Securities Litigation Reform Act of Actual results may differ materially from those indicated by such forward-looking statements as a result of various important factors, including the factors discussed in the "Risk Factors" section of our most recent 10-K filed with the SEC. In addition, the forward-looking statements included in this press release represent the Company's views as of April 11, The Company anticipates that subsequent events and developments will cause the Company's views to change. However, while the Company may elect to update these forward-looking statements at some point in the future, the Company specifically disclaims any obligation to do so. These forward-looking statements should not be relied upon as representing the Company's views as of any date subsequent to April 11, Blackboard, in its sole discretion, may delay or cancel the release of any product or functionality described in this presentation.

3 Overview Web Services Overview –High-level, not a detailed tutorial Relationship to Blackboard Building Blocks Consuming Web Services Creating Web Services

4 Audience Familiarity with Java Servlet programming Familiarity with HTTP Experience with Blackboard Building Blocks

5 Overview – Web Services Collection of inter-related technologies –SOAP. The basic protocol semantics. …definition of the XML-based information which can be used for exchanging structured and typed information between peers in a decentralized, distributed environment. –XML Schema. Type system for SOAP. –UDDI. Service discovery. –WSDL. Service description. In a nutshell, XML encoded method calls over HTTP

6 Web Services and Blackboard Building Blocks Perfect fit for heterogeneous computing… –Client to server, Server to server –Easy to understand and analyze –Well-supported Blackboard ® application can be either consumer or producer –Ideal model for standalone programs

7 Web Services and Blackboard Building Blocks Consumer –Add call out capability to your extensions Producer –Expose your methods via Web Services

8 Web Services and Blackboard Building Blocks Freely available Java-based toolkits –Axis (formerly IBM soap4j) –Sun Web Services Developer Kit –Other vendor solutions… Maps perfectly to deployment model –Toolkits designed for deployment in web apps

9 Web Services and Blackboard Building Blocks Blackboard Building Block deployment model has some unique advantages –Different extensions can implement their own Web Services… identical names –Axis can exist in multiple webapps, even with different versions

10 Challenges in Existing Architecture Session Management –Assumes stateful, browser-oriented clients –Cookie redirect Authentication –SOAP standards mute on credentials –Authentication APIs not generalized enough… –Authentication APIs not specific enough…

11 Web Services – Technical Issues API Granularity –Calls are expensive, incorporating the overhead of XML serialization Network (HTTP) communication XML de-serialization …and back again

12 Doing it Today… Blackboard Learning System App Pack 1 and higher incorporate.NET/CLR code for both API layer data access and Web Services (via.asmx) –Gain the benefits of CLR, ease of development with.NET tools Extensions can also package Java-based Web Services tool of choice –Local to web application –E.g., Apache Axis

13 Using Web Services Deploy to Blackboard Get Some WSDL Provided by the Web Service Generate Stubs E.g., wsdl2java Write code Using Stubs The code you write Package Webapp The standard B2 packaging

14 Configuration Standard Blackboard Building Block configuration –bb-manifest.xml –web.xml Requires outgoing socket connection permission

15 Configuration – Gotcha! client-config.wsdd must be readable by the extension (e.g., WEB-INF) –Set property first!

16 Configuration – Gotcha! You must declare additional permissions –RuntimePermission, accessDeclaredMembers –PropertyPermission, javax.wsdl.factory.WSDLFactory, write –RuntimePermission, getClassLoader –RuntimePermission, createClassLoader

17 Example Find a service to consume –MERLOT Web Search Service Use WSDL to generate Java stub classes –Wsdl2java – Takes a.wsdl file (or URL) and generates stub classes –Can be invoked via an Ant task…

18 Generating Stubs For typed invocation –Makes it easy to work within your language of choice; data mapped to language objects –Dynamic invocation also supported by most toolkits Axis – IBM wsdl4j –Ant task

19 Generating Stubs – Ant Task

20 Generating Stubs – Ant Task

21 Example – Permissions

22 Example – Using the Stubs String queryTerms = request.getParameter("queryTerms"); //get config file String fileName = getServletContext().getRealPath( "/WEB-INF/client- config.wsdd" ); AxisProperties.setProperty( EngineConfigurationFactoryDefault.OPTION_CLIENT_CONFIG_FILE, fileName ); GoogleSearchServiceLocator locator = new GoogleSearchServiceLocator(); GoogleSearchPort googleSearch = locator.getGoogleSearchPort(); GoogleSearchResult result = googleSearch.doGoogleSearch(... ); elements = result.getResultElements(); request.setAttribute( Constants.RESULTS_KEY, Arrays.asList( elements ) );...

23 Checklist Axis libraries client-config.wsdd Stub generator/stubs Client class with configuration to bootstrap properties Manifest with correct permissions

24 .NET APIs and Web Services CLR APIs introduced in Blackboard Academic Suite version used to expose basic Web Services, via ASP.NET Methods correspond to loaders/persisters in APIs Windows only

25 Using.NET API Web Services Example using Java Generate stubs –http://server/BlackboardWebServices/ AnnouncementWebService.asmx?wsdl Implement authentication –Currently only supports Blackboard authentication –Credentials passed via SOAP header

26 Using.NET Web Services BbAnnouncementWSSoapStub webService = (BbAnnouncementWSSoapStub) newBbAnnouncementWSLocator().getBbAnnouncementWSSoap(); String passHash = webService.getMD5Hash( PASSWORD ); SOAPHeaderElement authHeader = new SOAPHeaderElement( null, "BbAuthentication" ); authHeader.addChildElement( "bbUser" ).addTextNode( "administrator" ); authHeader.addChildElement( "bbPassword" ).addTextNode( passHash ); authHeader.addChildElement( "bbAuthenticationType" ); webService.setHeader( authHeader ); Announcement[] list = webService.loadByCourseId( courseId ).getAnnouncement();

27 Generating Web Services Decide on the methods you want to support –Chunky is better; return a lot of data in few calls Create Java classes that implement the interface

28 Web Service Class public class CourseManager { public CourseWrapper[] getCourseList( String userName ) { //… work goes here }

29 Axis Tasks Implement Class Configure Axis deployment descriptor (server-config.wsdd) –Defines service name –Point to web service class and set parameters for which methods are the web service methods Implement handlers –Objects that perform Blackboard-specific processing. E.g., setContext()

30 Configuring Axis Must specify server-config.wsdd –Again, this is because the protocol doesnt handle SecurityException Add handlers for Blackboard-specific requirements –Authentication, Session, Context –But… no common Servlet/JSP entry point

31 server-config.wsdd Declaring the service…

32 Custom Axis Handlers Chain of Responsibility design pattern Can be configured per service, or globally within the webapp ServletFilter can be used instead of handler

33 Example – server-config.wsdd

34 Example – Custom Handler public class ContextSetHandler extends BasicHandler { public void invoke( MessageContext msgCtx ) throws AxisFault { try { ContextManager ctxMgr = (ContextManager)BbServiceManager.lookupService(ContextManager.class); HttpServletRequest request = (HttpServletRequest)msgCtx.getProperty( HTTPConstants.MC_HTTP_SERVLETREQUEST ); ctxMgr.setContext( request ); } catch (Exception e) { //... }

35 Configuration – Gotcha WSDLFactory and permissions –Create bootstrap servlet to init system property; factory locator does not recover from file system security Reflection permissions –Axis uses reflection extensively to auto- map the Java class to WSDL and negotiate the end point

36 Using the Web Service WSDL URL: –http://server/webapps/bb-service- bb_bb60/services/ServiceName?wsdl Use as input to wsdl2java

37 Checklist Class to implement web service Class to provide handler functionality Axis libraries server-config.wsdd Configuration/Bootstrap servlet Manifest with correct permissions

38 Great. Now What? Well, this is where truly heterogeneous programming comes in… Sample Java Client Sample.NET Client

39 Sample Java Client WSDL URI Wsdl2java (Ant) Stubs + your code javac Your program

40 Sample Java Client package blackboard.client; public class SampleClient { public static void main( String[] args ) { try { CourseManagerServiceLocator locator = new CourseManagerServiceLocator(); CourseManager service = locator.getCourseManager(); CourseWrapper[] list = service.getCourseList(... ); for ( int i = 0; i < list.length; i++ ) { System.out.println( list[i].getCourseId() ); } } catch( Exception e ) { } } }

41 Sample.NET Client WSDL URIWsdl.exe Stubs + your code Csc.exe Your program

42 Sample.NET Client using System; namespace Blackboard.Client { public class ServiceClient { public static void Main( string[] args ) { try { CourseManagerService service = new CourseManagerService(); CourseWrapper[] list = service.getCourseList(... ); System.Console.WriteLine( list.Length + " courses found." ); foreach (CourseWrapper course in list ) { System.Console.WriteLine( course.courseId ); } } catch( Exception e ) {} } } }

43 Conclusion Web Services are available today –In different flavors, even Some pitfalls Promises an entirely new class of application for Blackboard

44 Thank You!


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