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WebService

WebService. Outline. Overview of Web Services SOAP (messaging) WSDL (service description) UDDI (registry). What are Web Services ?. Web services are modular web applications that provide data and services to other applications over the web

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WebService

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  1. WebService

  2. Outline • Overview of Web Services • SOAP (messaging) • WSDL (service description) • UDDI (registry)

  3. What are Web Services ? • Web services are modular web applications that provide data and services to other applications over the web • Web services apply web technologies such as HTTP and XML to the concepts of distributed computing technologies such as CORBA and DCOM RATS Oct 2002 CS@UGA

  4. Web Services: Some Definitions • A Web Service is a URL-addressable software resource that performs functions (or a function). • "Web services are a new breed of Web application. They are self-contained, self-describing, modular applications that can be published, located, and invoked across the Web. Web services perform functions, which can be anything from simple requests to complicated business processes. … Once a Web service is deployed, other applications (and other Web services) can discover and invoke the deployed service.” IBM web service tutorial

  5. "server" "naming service" "client" Web Service Architecture Service provider bind (SOAP) publish (WSDL) Service requestor Service broker find (UDDI)

  6. How Web Services work? • Web services are standards-based software components that can be accessed over the Internet. Step 1: Service providers (producer) maintain/publish information about their services in a registry Step 2: Service requesters (consumer) search registries for services Step 3: Once found, a service can be invoked based on open Internet standards irrespective of differences in platforms, programming model, programming languages between consumer and producer RATS Oct 2002 CS@UGA

  7. Web Services Standards With the following technologies, it is possible to build standards-based systems that are truly interoperable. • UDDI: Universal Description, Discovery and Integration. • UDDI registry stores descriptions about companies and the services they offer in a common XML format. (for web services publishing and discovery) • WSDL: Web Services Description Language (new: DAML-S) • WSDL is an XML-based format for specifying the interface to a web service. (for web services description) • SOAP: Simple Object Access Protocol • SOAP is the XML-based protocol for sending requests and responses to and from web services. (for web services invocation) RATS Oct 2002 CS@UGA

  8. Simple Web Service Invocation Service Requestor courtesy:http://www.cs.uga.edu/~sent/thesis/Final.ppt Remote Web Service Repository (Web Sites) 2 Manual Web Service Lookup HTTP GET 3 WSDL File Write Client Code 1 Remote Web service 4 SOAP Request Invoke Web Service Publish Web Service 5 SOAP Response RATS Oct 2002 CS@UGA

  9. Web Services Implementation Web Service Provider (endpoint) • Application Server (web service-enabled) • provides implementation of services and exposes it through WSDL/SOAP • implementation in Java, as EJB, as .NET (C#) etc. • SOAP server • implements the SOAP protocol • HTTP server • standard Web server • SOAP client • implements the SOAP protocol on the client site HTTP server SOAP server application server Requestor (SOAP client) SOAP messages (http transport)

  10. WSDL* Structure Service • Service • collection of endpoints • endpoints= port + binding • Port type set of operations supported by endpoints • Operations abstract description of action supported by service • Binding maps abstract specification to specific protocol • Ports network address/URI that implements service • Message typed definition of data communicated * Used in conjunction with UDDI registry and can be compared with IDL courtesy: http://www.llnl.gov/CASC/workshops/components_2001/viewgraphs/FranciscoCurbera.ppt Port (e.g. http://host/svc) Port Binding (e.g. SOAP) Binding Abstract interface portType operation(s) inMesage outMessage RATS Oct 2002 CS@UGA

  11. WSDL File Provides explicit representation of available protocols while in OMG model, protocol is fixed at the time ORB infrastructure is deployed. Protocol specification is not visible to application or developer Abstract Description Concrete Description RATS Oct 2002 CS@UGA

  12. SOAP: Simple Object Access Protocol • XML based lightweight protocol for the exchange of information in a decentralized, distributed environment • What's so special about SOAP ? • platform independent • gets over firewall issues • Why do we need it ? • today's applications communicate using RPC using HTTP. But HTTP is not designed for this.  introduces security and compatibility issues  firewalls typically block • How ? • XML based messages (simple text and nothing else) RATS Oct 2002 CS@UGA

  13. SOAP: • SOAP defines a framework for message structure and a message-processing model • Does not define application semantics • Enables trans-operating system RPCs • Used over HTTP, SMTP, FTP, MQSeries, Jabber, JMS etc <?xml version="1.0" encoding="UTF-8" ?> <env:Envelope xmlns:env="http://www.w3.org/2001/09/soap-envelope"> <env:Header> <n:alertcontrol xmlns:n="http://example.org/alertcontrol"> <n:priority>1</n:priority> <n:expires>2001-06-22T14:00:00-05:00</n:expires> </n:alertcontrol> </env:Header> <env:Body> <m:alert xmlns:m="http://example.org/alert"> <m:msg>Pick up Mary at school at 2pm</m:msg> </m:alert> </env:Body> </env:Envelope> courtesy: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnsoapspec/html/soapspecindex.asp RATS Oct 2002 CS@UGA

  14. UDDI • A shared public registry implementation based on a set of public specifications • Specification for registry also defines a SOAP-based web service for locating WSDL-formatted protocol descriptions of web services • Two types of information are registered within UDDI. The first is the set of abstract service protocols, called tModels (technical models), which are used to describe the behavior of a web service. The second type of information in UDDI is the service implementation, currently referred to as a businessEntity. These entries refer to multiple tModels and provide descriptions about their behavior and specifications. RATS Oct 2002 CS@UGA

  15. Contoh

  16. WSDL • Ditunjukkandigambardibawahini • Cobaamatidenganklas Java sebelumnya

  17. WSDL

  18. SOAP • Ditunjukakndalamgambardibawahini • Cobaamatidenganmeninjau file WSDL di slide sebelumnya

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