Web Services and Blackboard

Bob Alcorn

Blackboard, Inc.

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 1995. 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, 2005. 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, 2005. Blackboard, in its sole discretion, may delay or cancel the release of any product or functionality described in this presentation.

Overview

• Web Services Overview– High-level, not a detailed tutorial

• Relationship to Blackboard Building Blocks™

• Consuming Web Services

• Creating Web Services

Audience

• Familiarity with Java Servlet programming

• Familiarity with HTTP

• Experience with Blackboard Building Blocks

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

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

Web Services and Blackboard Building Blocks

• Consumer– Add “call out” capability to your extensions

• Producer– Expose your methods via Web Services

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

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

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…

Web Services – Technical Issues

• API Granularity– Calls are expensive, incorporating the

overhead of• XML serialization• Network (HTTP) communication• XML de-serialization• …and back again

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

Using Web Services

Deploy toBlackboard

Get SomeWSDL

Provided by the Web Service

GenerateStubs

E.g., wsdl2java

Write codeUsing Stubs

The code you write

PackageWebapp

The standard B2 packaging

Configuration

• Standard Blackboard Building Block configuration– bb-manifest.xml– web.xml

• Requires outgoing socket connection permission <permission type=“socket” name=“api.google.com” actions=“connect”/>

Configuration – Gotcha!

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

Configuration – Gotcha!

• You must declare additional permissions– RuntimePermission,

accessDeclaredMembers– PropertyPermission,

javax.wsdl.factory.WSDLFactory, write– RuntimePermission, getClassLoader– RuntimePermission, createClassLoader

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…

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

Generating Stubs – Ant Task

<path id="axis.classpath"> <fileset dir="${axis.home}/lib"> <include name="**/*.jar"/> </fileset> </path> <taskdef resource="axis-tasks.properties"

classpathref="axis.classpath"/>

Generating Stubs – Ant Task

<axis-wsdl2java output="src“verbose="true“url=“${merlot.wsdl}”>

<mapping

namespace="http://www.blackboard.com/ls/webservices/“package="blackboard.client"/>

<mapping namespace="http://localhost/webapps/bb-webservice-bb_bb60/services/CourseManager" package="blackboard.client"/>

</axis-wsdl2java>

Example – Permissions

<permissions> <permission . . . /> <permission . . . />

<permission type="socket" name=“matanzas.merlot.org" actions="connect,resolve"/>

<permission type="runtime" name="accessDeclaredMembers" actions=""/>

<permission type="java.util.PropertyPermission" name="java.protocol.handler.pkgs" actions="write"/>

</permissions>

Example – Using the StubsString queryTerms = request.getParameter("queryTerms");

//get config fileString 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 ) );. . .

Checklist

• Axis libraries

• client-config.wsdd

• Stub generator/stubs

• Client class with configuration to bootstrap properties

• Manifest with correct permissions

.NET APIs and Web Services

• CLR APIs introduced in Blackboard Academic Suite™ version 6.1.5 used to expose basic Web Services, via ASP.NET

• Methods correspond to loaders/persisters in APIs

• Windows only

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

Using .NET Web ServicesBbAnnouncementWSSoapStub 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();

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

Web Service Class

public class CourseManager {

public CourseWrapper[] getCourseList( String userName ) { //… work goes here }

}

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()

Configuring Axis

• Must specify server-config.wsdd– Again, this is because the protocol doesn’t

handle SecurityException

• Add handlers for Blackboard-specific requirements– Authentication, Session, Context– But… no common Servlet/JSP entry point

server-config.wsdd

<service name="CourseManager" provider="java:RPC"><parameter name="allowedMethods" value="*"/><parameter name="className"

value="blackboard.webservice.CourseManager"/></service>

Declaring the service…

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

Example – server-config.wsdd

<transport name="http"> <requestFlow> <!-- . . . --> <handler type=

"java:blackboard.webservice.axis.ContextSetHandler"/> </requestFlow> <responseFlow> <handler type=

"java:blackboard.webservice.axis.ContextReleaseHandler"/>

</responseFlow></transport>

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) { // . . . } }}

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

Using the Web Service

• WSDL URL:– http://server/webapps/bb-service-

bb_bb60/services/ServiceName?wsdl

• Use as input to wsdl2java

Checklist

• Class to implement web service

• Class to provide handler functionality

• Axis libraries

• server-config.wsdd

• Configuration/Bootstrap servlet

• Manifest with correct permissions

Great. Now What?

• Well, this is where truly heterogeneous programming comes in…

• Sample Java Client

• Sample .NET Client

Sample Java Client

WSDL URIWsdl2java

(Ant)

http://localhost/webapps/vid-handle-bbuid/services/YourService?wsdl

Stubs + your code

javac

Your program

Sample Java Clientpackage 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 ) { } }}

Sample .NET Client

WSDL URI Wsdl.exe

http://yourserver/webapps/id-vid-bbuid/services/YourService?wsdl

Stubs + your code

Csc.exe

Your program

Sample .NET Clientusing 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 ) {} } }}

Conclusion

• Web Services are available today– In different flavors, even

• Some pitfalls

• Promises an entirely new class of application for Blackboard

Thank You!