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Web Services. Erdogan Dogdu CSC 4360/6360 Computer Science Department Georgia State University (Adapted from Mark Sapossnek (Boston Uni.) presentation). Learning Objectives. Understand the coming Web Services revolution Fundamentals of Web Services Be able to create and debug a Web Service

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Web Services


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    1. Web Services Erdogan DogduCSC 4360/6360 Computer Science Department Georgia State University (Adapted from Mark Sapossnek (Boston Uni.) presentation)

    2. Learning Objectives • Understand the coming Web Services revolution • Fundamentals of Web Services • Be able to create and debug a Web Service • Using the .NET Framework SDK • Using Visual Studio.NET • Using Sun Microsystem’s Java Web Services Development Pack (JWSDP)

    3. Agenda • Web Services Overview • Underlying Technologies • Developing a Web Service • Consuming Web Services • Miscellaneous • .NET My Services • Demo using Sun’s JWSDP

    4. Web Services OverviewBusiness Today • CEO challenges • Revamp customer service • Overhaul supply chain • Speed up the decision process • CIO challenges • Reorient IT architecture • Connect with a limitless number of external constituents • Extend processes to external constituents

    5. Web Services OverviewInternet Business Processes Span Companies

    6. Web Services Overview Technology Fabric Must Span Companies Too

    7. Web Services Overview Drivers • Companies, suppliers, partners, and customers must be able to work together • Faster than ever before • Over the Internet • Or risk “death by isolation” • Leverage Internet cost structure

    8. Web Services Overview Possible Solutions • Distributed computing • Web sites (portals) • Web Services

    9. Web Services Overview Distributed Computing • Client/server model • Doesn‘t scale • Not secure • Distributed object model • Components: packaging and interoperability • Remoting: remote method invocation • COM, CORBA, Java RMI and EJB • Not Internet-friendly • Interoperability issues: poor/non-existent standards • Tightly coupled: still doesn‘t scale

    10. Web Services Overview Distributed Computing • 3-tier Application Architecture • Great way to build scalable Web applications • But such applications are silos • Integration is an afterthought • They can be integrated behind the firewall • Even that can be a problem • They do not provide a way to integrate across the firewall (i.e. over the Internet)

    11. Web Services Overview Portals Ads Mail Other Svcs Calendar Weather Finance News

    12. Web Services OverviewPortal Limitations • No standard way to expose functionality • Integration is expensive and error-prone • Hard to outsource • Not designed to be used outside original scope • The problem? • HTML is designed for presentation to people • Can’t repurpose it in a general, reliable way • Don’t even think about screen scraping

    13. Web Services OverviewWhat Is a Web Service? • The solution? Web Services! • A Web Service exposes functionality to a consumer • Over the Internet or intranet • A programmable URL • Functions you can call over the Internet • Based on Web standards • HTTP, XML, SOAP, WSDL, UDDI, with more to come • Can be implemented in any language on any platform • Black boxes • Component-like, reusable

    14. Web Services OverviewWhat Is a Web Service? • A Web Service combines the best features of distributed computing and portals and eliminates the worst • Provides a mechanism for invoking methods remotely • Uses Web standards (e.g. HTTP, XML) to do so

    15. Web Services OverviewWhat Is a Web Service? • Web Services allow you to interconnect: • Different companies • Many/any devices • Applications • Different clients • Not just browsers • Distribution and integration of application logic • Enable the programmable Web • Not just the purely interactive Web • Web Services are loosely coupled

    16. Web Services OverviewWhat is a Web Service? • New paradigm for Internet development • Deliver applications as services • Richer, customer-driven experience • Continuous delivery of value/bits • Third-generation Internet

    17. HTML, XML HTML, XML HTML HTML Generation 1Static HTML Generation 2Web Applications Generation 3Web Services Web Services OverviewEvolution of the Web

    18. Web Services Overview Benefits • Everyone • Leverage existing infrastructure • “Build or buy” development decisions • Minimize development time/costs • Enterprises • Integration imperative • Dynamic, easy B2B relationships • New Web-based businesses • Greater personalization • New services/new revenue streams • Be “everywhere” vs. single destination

    19. Web Services Overview Possibilities • Scenario: Planning a trip • Go to Expedia site (or Travelocity, or …) • Log in. • Find the flights you want • Don’t have to reenter seat/meal/airline/frequent flyer/… info • System can find lowest price fare by looking at your calendar(s) • Purchase tickets w/o entering credit card # • Flight info automatically added to your calendar and your spouse’s calendar • Book rental car/hotel w/your preferences; added to calendar • On day of trip get notified of flight status via email/toast/pager/cell phone

    20. Web Services OverviewApplication Model Partner Web Service Other Web Services Partner Web Service Internet + XML End Users YourCompany.com Application Business Logic Tier Data Access and Storage Tier Other Applications

    21. Web Services OverviewSample Web Services • E-commerce: order books, office supplies, other products • Track packages: UPS, FedEx • Weather • Maps • Telephone redirection, customizable rules and messages

    22. Agenda • Web Services Overview • Underlying Technologies • Developing a Web Service • Consuming Web Services • Miscellaneous • .NET My Services

    23. Underlying TechnologiesXML Is the Glue XML HTML TCP/IP Technology Connecting Applications Connectivity Presentation FTP, E-mail, Gopher Innovation Web Pages Connect the Web Web Services Browse the Web Program the Web

    24. Underlying TechnologiesWeb Services Stack (Standards) Directory: Publish & Find Services: UDDI Description: Formal Service Descriptions: WSDL Wire Format: Service Interactions: SOAP Universal Data Format: XML Ubiquitous Communications: Internet Simple, Open, Broad Industry Support

    25. Underlying TechnologiesWeb Services Stack • Discovery • Directory allows potential clients to locate relevant Web Services • UDDI • A Description language defines the format of methods provided by a Web Service • WSDL

    26. Underlying TechnologiesWeb Services Stack UDDI Directory http://www.uddi.org UDDI or other directory service Locate a Service Link to Discovery Document (XML) Web Service Client WSDL Description http://www.ibuyspy.com/ibuyspycs/InstantOrder.asmx?wsdl Request Service Description Web Service Return Service Description (XML) SOAP Wire Format Request Service Return Service Response (XML)

    27. Underlying TechnologiesWeb Service Wire Format • The Web Service Wire Format specifies how specific messages are exchanged • HTTP-GET • HTTP-POST • SOAP • HTTP-GET and HTTP-POST use a minimal HTTP interface to invoke Web Services • Limited support for data types • SOAP provides a robust HTTP/XML interface • Extensive support for data types

    28. XML OverviewXML Basics • XML is designed to represent and transfer structured data • In HTML: <p>Jan 15, 2000 </p> • In XML: <OrderDate>Jan 15, 2000</OrderDate> • XML does not display or transform data • XML separates data from formatting and transforming • HTML and XML are both derived from SGML • In different ways

    29. XML OverviewXML Syntax • XML is composed of tags and attributes • Tags can be nested • Representing entities, entity properties, and entity hierarchy <ROOT> <Orders OrderID="10643" CustomerID="ALFKI" EmployeeID="6" OrderDate="1997-08-25T00:00:00" RequiredDate="1997-09-22T00:00:00" ShippedDate="1997-09-02T00:00:00" /></ROOT>

    30. XML OverviewXML Schemas • XML schemas describe the structure of an XML document • XML schemas describe the tag and attribute specifications • Simple and compound data types • XML schemas also describe constraints on the contained text • XML schemas and the DTD are mutually exclusive

    31. SOAP Overview • A lightweight protocol for exchanging information in a distributed, heterogeneous environment • It enables cross-platform interoperability • Interoperable • OS, object model, programming language neutral • Hardware independent • Protocol independent • Works over existing Internet infrastructure

    32. SOAP Overview • Guiding principle: “Invent no new technology” • Builds on key Internet standards • SOAP ≈ HTTP + XML • SOAP 1.2, W3C working draft • Tutorial:http://www.w3.org/TR/2002/WD-soap12-part0-20020626/ • The SOAP specification defines: • The SOAP message format • How to send messages • How to receive responses • Data encoding

    33. SOAP SOAP Is Not… • Objects-by-reference • Message-oriented • Complicated • Doesn’t try to solve every problem in distributed computing • Can be easily implemented

    34. SOAPThe HTTP Aspect • SOAP requests are HTTP POST requests POST /WebCalculator/Calculator.asmx HTTP/1.1 Content-Type: text/xml SOAPAction: “http://tempuri.org/Add” Content-Length: 386 <?xml version=“1.0”?> <soap:Envelope ...> ... </soap:Envelope>

    35. SOAPMessage Structure The complete SOAP message SOAP Message Protocol binding headers Headers <Envelope> encloses payload SOAP Envelope <Header> encloses headers SOAP Header Individual headers Headers <Body> contains SOAP message name SOAP Body Message Name & Data XML-encoded SOAP message name & data

    36. SOAPSOAP Message Format • An XML document using the SOAP schema: <?xml version=“1.0”?> <soap:Envelope ...> <soap:Header ...> ... </soap:Header> <soap:Body> <Add xmlns=“http://tempuri.org/”> <n1>12</n1> <n2>10</n2> </Add> </soap:Body> </soap:Envelope>

    37. SOAPServer Responses • Server replies with a “result” message: HTTP/1.1 200 OK ... Content-Type:text/xml Content-Length: 391 <?xml version=“1.0”?> <soap:Envelope ...> <soap:Body> <AddResult xmlns=“http://tempuri.org/”> <result>28.6</result> </AddResult> </soap:Body> </soap:Envelope>

    38. SOAPEncoding Complex Data • Data structures are serialized as XML: <soap:Envelope ...> <soap:Body> <GetStockDataResult xmlns=“http://tempuri.org/”> <result> <Description>Plastic Novelties Ltd</Description> <Price>129</Price> <Ticker>PLAS</Ticker> </result> </GetStockDataRseult> </soap:Body> </soap:Envelope>

    39. SOAPSecurity and Features • Builds on HTTP Security • HTTPS • Developers / IT choose which methods to expose explicitly • Does not pass application code • Firewall-friendly • Type safe

    40. Sun Microsystems DevelopMentor Inc. Digital Creations IONA Technologies PLC Jetform ObjectSpace Inc. Rockwell Software Inc. SAP Compaq Microsoft Rogue Wave Software Inc. Scriptics Corp. Secret Labs AB UserLand Software Inc. Zveno Pty. Ltd. IBM Hewlett Packard Intel SOAPIndustry Support

    41. SOAPExample of a SOAP Request POST /StockQuote HTTP/1.1 Host: www.stockquoteserver.com Content-Type: text/xml; charset="utf-8" Content-Length: nnnn SOAPAction: "Some-URI“ <SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" SOAP-ENV: encodingStyle = "http://schemas.xmlsoap.org/soap/encoding/"> <SOAP-ENV:Body> <m:GetLastTradePrice xmlns:m="Some-URI"> <symbol>DIS</symbol> </m:GetLastTradePrice> </SOAP-ENV:Body> </SOAP-ENV:Envelope>

    42. SOAPExample of a SOAP Response HTTP/1.1 200 OK Content-Type: text/xml; charset="utf-8" Content-Length: nnnn <SOAP-ENV:Envelope xmlns:SOAP-ENV= "http://schemas.xmlsoap.org/soap/envelope/" SOAP-ENV: encodingStyle= "http://schemas.xmlsoap.org/soap/encoding/"/> <SOAP-ENV:Body> <m:GetLastTradePriceResponse xmlns:m="Some-URI"> <Price>34.5</Price> </m:GetLastTradePriceResponse> </SOAP-ENV:Body> </SOAP-ENV:Envelope>

    43. SOAPExample of a SOAP Error HTTP/1.1 500 Internal Server Error Content-Type: text/xml; charset="utf-8" Content-Length: nnnn <SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"> <SOAP-ENV:Body> <SOAP-ENV:Fault> <faultcode> SOAP-ENV: MustUnderstand </faultcode> <faultstring>SOAP Must Understand Error </faultstring> </SOAP-ENV:Fault> </SOAP-ENV:Body> </SOAP-ENV:Envelope>

    44. WSDLWeb Services Description Language • XML schema for describing Web Services • Service interface definition • Abstract semantics for Web Service • Service implementation definition • Concrete end points and network addresses where Web Service can be invoked • Clear delineation between abstract and concrete messages

    45. WSDLWSDL Schema Interface Implementation <definitions> <definitions> <import> <import> <types> <service> <message> <port> <portType> <binding>

    46. WSDLWSDL Schema • <definitions> are root node of WSDL • <import> allows other entities for inclusion • <types> are data definitions - xsd • <message> defines parameters of a Web Service function • <portType> defines input and output operations • <binding> specifies how each message is sent over the wire Interface <definitions> <import> <types> <message> <portType> <binding>

    47. WSDLWSDL Schema Implementation • <service> specifies details about the implementation • <port> contains the address itself <definitions> <import> <service> <port>

    48. WSDL WSDL Elements • Open – allows for other namespaces and thus highly extensible • Ability to import other schemas & WSDL • Provides “recipe” for Web Services • Provides both interface and implementation details • Allows for separation of the two

    49. WSDL Example • Demo: MyHello service on db.gsu.edu http://db.gsu.edu:8080/hello-jaxrpc/hello?WSDL

    50. UDDIOverview • UDDI = Universal Description, Discovery, and Integration • Industry Initiative to address discovery • A registration database for Web Services • Specifications • Schema for service providers and descriptions • API for publishing and searching • Developed on industry standards (XML, HTTP, TCP/IP, SOAP) • Applies to both XML and non-XML services • Implementation • Public and private instances of specification