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Web Services

Explore the concept of Service-Oriented Architecture (SOA) and how Web services provide a solution for integrating different systems and programming languages. Learn about the technologies behind Web services, such as XML, SOAP, WSDL, and UDDI, and discover their benefits for integration, access, flexibility, and application assembly. Use tools like WebSphere Studio Wizards to easily create and use Web services.

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Web Services

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  1. Web Services Distributed Systems

  2. Service Oriented Architecture • Service-Oriented Architecture (SOA) expresses a software architectural concept that defines the use of services to support the requirements of software users

  3. Service Oriented Architecture Service Provider Service Requestor Internet Legacy System Service Broker

  4. Requirements for a SOA • Interoperability between different systems and programming languages • Clear and unambiguous description language • Retrieval of the service • Security

  5. Web Services: DefinitionW3C • A Web service is a software system • Identified by a URL, whose public interfaces and bindings are defined and described using XML. • Its definition can be discovered by other software systems • These systems may then interact with the Web service • using XML based messages conveyed by Internet protocols • Web Services implement a Service Oriented Architecture

  6. Web Services • Web services are an emerging technology that offer a solution for providing a common collaborative architecture. • Web services provide functional building blocks which are not tied to any particular programming language or hardware platform. • They are accessible over standard Internet protocols.

  7. The Evolution • Online systems replace Batch systems • Graphical User Interfaces replace “green” screens • Networked systems replace standalone systems • Internet based systems replace LAN based systems • Future ??? • Web Services replace simple Internet and LAN based systems

  8. Technologies • XML (eXtensible Markup Language) • markup language that underlies most of the specifications used for Web services.   • SOAP (Simple Object Access Protocol) • (Simple Object Access Protocol), similar to JDBC, is a network, transport, and programming language and platform neutral protocol that allows a client to call a remote service. The message format is XML. • WSDL (Web services description language) • An XML-based interface and implementation description language. The service provider uses a WSDL document in order to specify the operations a Web service provides.  • UDDI (universal description, discovery, and integration) • Both a client-side API and a SOAP-based server implementation that can be used to store and retrieve information on service providers and Web services.

  9. How it works • A Web Service is a URL-addressable software resource that performs functions (or a function). • Web Services communicate using standard protocol known as SOAP (Simple Object Access Protocol). • A Web Service is located by its listing in a Universal Discovery, Description and Integration (UDDI) directory.

  10. Technologies

  11. What are Web Services good for? Integration • In a lot of organizations, the data and logic of one application are basically useless to other applications. • When an application and its data are isolated from other applications, we often say that they are in “silos.” • Web Services are better at sharing data and functions. • The result is that the “silos” come down, and previously isolated systems can talk to each other.

  12. What are they good for? Access • Web Services are especially good at providing access through different interfaces. • A Web Service can have a dedicated client application, but it can also be readily accessed through browsers, wireless devices, voice-activated interfaces, and so on. • Adding new access methods is much simpler than with a traditional application.

  13. What are they good for? Flexibility • One of the more important innovations in Web Services is “machine-to-machine communications.” • This means that a Web Service can ask another Web Service to do something, and that Web Service can ask another Web Service to do something, and so on. • In the future, many Web Services will really just be aggregations of other Web Services.

  14. What are they good for? Application Assembly • Future applications will be assembled from a diverse group of web services, aggregating functionality. • Reusability is extended to the execution level, versus reusability from just the design and construction level.

  15. SOAP • Simple Object Access Protocol • SOAP is an open protocol specification defining a uniform way of performing RPCs using HTTP as the underlying communications protocol with XML for the data serialization.

  16. WSDL (“Web Service Description Language”) XML-based Submitted to W3C for standardization Terraserver example http:terraserver.microsoft.com/default.aspx How Is a Service Described?

  17. How Do I Find Web Services? • UDDI project by Microsoft, IBM, and others. Take a look at //uddi.org • Websites • //www.xmethods.net • //www.salcentral.com

  18. XMethods

  19. Currency Exchange

  20. Using the Currency Exchange Web Service Currency Exchange WS RV Application Internet

  21. WebSphere Studio Wizards • Wizards make it easy for you to create and use Web Services • Wizard to create a Web Service from a JavaBean • Generates WSDL document • Creates all required software components • Create a Test client • Wizard to create a Web Service Client • Use the WSDL document as input

  22. Generate a Web Service Client

  23. Web Service Client

  24. Web Service Client

  25. Testing Input.jsp Method.jsp Result.jsp

  26. conversion.html

  27. conversion.html <IFRAME src="Input.jsp?method=getRate"name="inputs" scrolling="no" frameborder="0" height="250"></IFRAME> <IFRAME src="Result.jsp" name="result" scrolling="no" frameborder="0"></IFRAME>

  28. conversion.html

  29. Currency conversion

  30. Lab Exercises • Create Web Services client • Integrate Web Service into the RV application

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