Presentation on theme: "Understand Web Services"— Presentation transcript:
1 Understand Web Services LESSON 4.4Software Development FundamentalsUnderstand Web Services
2 Lesson Overview Students will understand Web services. In this lesson, you will learn about:Web services consumed by client applicationsAccessing Web services from a client applicationSOAP and WSDL
3 Guiding QuestionsHow are Web services accessed and consumed by client applications?What is SOAP?What is WSDL?
4 ActivatorHow would you communicate with someone who did not speak your language?How is this similar to how applications interact with Web services?(Answers will vary, but should resemble the following.) Find a common method and meaning of communication. You may have your own languages, but you can agree on using certain signs and gestures and their meaning.To interact with a Web service, you have to figure out how and what you will communicate (WSDL) and then actually communicate it using these tools (SOAP).
5 Review TermsSOAP—acronym for Simple Object Access Protocol, a simple, XML-based protocol for exchanging structured and type information on the WebWSDL—acronym for Web Services Description Language, an Extensible Markup Language (XML) format that allows for better interoperability among Web services and development tools
6 Web ServicesExtend the World Wide Web infrastructure to provide a means for software to connect to other applicationsAllow applications to access Web services via Web protocols and data formats such as Hypertext Transfer Protocol (HTTP), XML, and SOAPNo need to worry about how each Web service is implementedCombine the best aspects of component-based development and the WebA cornerstone of the Microsoft .NET Framework programming model6
7 What is a Web service?Used when a program wants to interact with another program through the Internet.A program is required to process the communication.The program might change its implementation from one language to another, but the functionality of the Web service stays the same.The Web service is the abstract functionality.The software and hardware is the concrete implementation.The move to service-oriented communication has changed software development. Viewing services as a distinct software abstraction is fundamental to service-oriented architecture (SOA), an approach that many organizations are putting in place today. Whether implemented using SOAP or in some other way, applications that interact through services are becoming the norm.7
8 What do Web services do?Provide reusable operations for other applicationsCan serve as a component of another applicationExamples: weather reports, currency conversionProvide interoperability between different platforms by giving applications a way to communicate8
9 How does a Web service work? A company (the requester) wants to use the Web service of another company (the provider) .Before they can pass information to each other, the requester and provider must agree on both the meaning and method of the information exchange.The method of exchange is documented in an interface described in a machine-processable format such as WSDL.Outside systems interact with the Web service in a manner prescribed by WSDL using SOAP.9
10 WSDLIt is written in XML and is used to locate a Web service and describe its functions.It defines the information formats, data types, transport protocols, and transport serialization formats.Source of table:ElementMeaning<types>The data types used by the Web service<message>The messages used by the Web service<portType>The operations performed by the Web service<binding>The communication protocols used by the Web service10
11 SOAPA generalized XML messaging framework for exchanging structures and type information on the Web (over HTTP).It contains no application or transport semantics, which makes it highly modular and extensible.To access a Web service, you use SOAP.It basically is a message-sending format that is language- and platform-independent to make it flexible and extensible. To access a Web service, you use SOAP. To clean your hands, you use soap.While SOAP is a protocol for exchanging messages, REST is an architectural style for building client-server applications. Students should review REST as another approach to implementing Web services.11
12 SOAP (continued)A SOAP message is an XML document containing the elements in the table.ElementMeaning<soap:Envelope>Identifies the XML document as a SOAP message<soap:Header>Header information<soap:Body>Call and response information<soap:Fault>Errors and status information12
13 Lesson ReviewA company wants to provide a Web service that allows outside applications to access sports statistics. Draw a diagram showing the interaction of WSDL and SOAP in the context of this Web service. Include labels for the requester and the provider, and use arrows to illustrate the flow of information.WSDL tells people what a Web service has to offer and how to locate it, while SOAP tells people how to communicate with it. A sample answer can be seen on the next slide.The Web service provider will provide a WSDL file to the requester so that the requester can format data properly when sending a request, as well as parse the data that is returned. If more information is required to perform this assessment, students should do additional research.An alternative assignment could be to show how a server might use a Web service to get information and then incorporate it into a Web site, which is then sent to a browser.
14 Requester refers to WSDL Web ServiceProviderRequesterSOAPAnswer to the lesson review question on the previous slide.Requester refers to WSDLWSDL