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Web Services

Web Services. Darshan R. Kapadia Gregor von Laszewski. What are Web Services?. A Web service (also Web Service ) is defined by the W3C as "a software system designed to support interoperable machine-to-machine interaction over a network".

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Web Services

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  1. Web Services Darshan R. Kapadia Gregor von Laszewski http://grid.rit.edu

  2. What are Web Services? • A Web service (also Web Service) is defined by the W3C as "a software system designed to support interoperable machine-to-machine interaction over a network". • Web Services can convert your application into a Web-application, which can publish its function or message to the rest of the world. http://en.wikipedia.org/wiki/Web_service http://grid.rit.edu

  3. What are Web Services? • Web services are application components • Web services communicate using open protocols • Web services are self-contained and self-describing • Web services can be discovered using UDDI(Universal Description, Discovery and Integration) • Web services can be used by other applications • XML is the basis for Web services http://grid.rit.edu

  4. Interoperability has Highest Priority!! • When all major platforms could access the Web using Web browsers, different platforms could interact. For these platforms to work together, Web-applications were developed. • Web-applications are simple applications that run on the web. These are built around the Web browser standards and can be used by any browser on any platform. • By using Web services, your application can publish its function or message to the rest of the world. • Web services use XML to code and to decode data, and SOAP to transport it (using open protocols). http://grid.rit.edu

  5. Elements of Web Services • The basic Web services platform is XML + HTTP. • XML provides a language which can be used between different platforms and programming languages and still express complex messages and functions. • The HTTP protocol is the most used Internet protocol. • Web services platform elements: • SOAP (Simple Object Access Protocol) • UDDI (Universal Description, Discovery and Integration) • WSDL (Web Services Description Language) http://grid.rit.edu

  6. What is SOAP? SOAP stands for Simple Object Access Protocol SOAP is an XML-based protocol to let applications exchange information over HTTP. SOAP is a protocol for accessing a Web Service. SOAP is a communication protocol SOAP is a format for sending messages SOAP is designed to communicate via Internet SOAP is platform independent SOAP is language independent SOAP is based on XML

  7. What is WSDL? • WSDL stands for Web Services Description Language • WSDL is an XML-based language for locating and describing Web services. • WSDL is based on XML • WSDL is used to describe Web services • WSDL is used to locate Web services http://grid.rit.edu

  8. What is UDDI? • UDDI stands for Universal Description, Discovery and Integration • UDDI is a directory service where companies can register and search for Web services. • UDDI is a directory for storing information about web services • UDDI is a directory of web service interfaces described by WSDL • UDDI communicates via SOAP • UDDI is built into the Microsoft .NET platform

  9. Example of Web Service

  10. WHY SOAP? • Today's applications communicate using Remote Procedure Calls (RPC) between objects like DCOM and CORBA, but HTTP was not designed for this. RPC represents a compatibility and security problem; firewalls and proxy servers will normally block this kind of traffic. • A better way to communicate between applications is over HTTP, because HTTP is supported by all Internet browsers and servers. SOAP was created to accomplish this. • SOAP provides a way to communicate between applications running on different operating systems, with different technologies and programming languages. http://grid.rit.edu

  11. SOAP Building Blocks • A SOAP message is an ordinary XML document containing the following elements: • An Envelope element that identifies the XML document as a SOAP message • A Header element that contains header information • A Body element that contains call and response information • A Fault element containing errors and status information

  12. Skeleton SOAP Message

  13. The SOAP Envelope Element • The SOAP Envelope element is the root element of a SOAP message. • The required SOAP Envelope element is the root element of a SOAP message. This element defines the XML document as a SOAP message. http://grid.rit.edu

  14. The SOAP Header Element • The SOAP Header element contains header information. • The optional SOAP Header element contains application-specific information (like authentication, payment, etc) about the SOAP message. • If the Header element is present, it must be the first child element of the Envelope element. http://grid.rit.edu

  15. The SOAP Body Element The required SOAP Body element contains the actual SOAP message intended for the ultimate endpoint of the message. <?xml version="1.0"?><soap:Envelopexmlns:soap="http://www.w3.org/2001/12/soap-envelope"soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding"><soap:Body>  <m:GetPrice xmlns:m="http://www.w3schools.com/prices">    <m:Item>Apples</m:Item>  </m:GetPrice></soap:Body></soap:Envelope>

  16. The SOAP Fault Element • The SOAP Fault element hold errors and status information for a SOAP message. • The optional SOAP Fault element is used to indicate error messages. • If a Fault element is present, it must appear as a child element of the Body element. • A Fault element can only appear once in a SOAP message. http://grid.rit.edu

  17. The SOAP Fault Element-Sub Elements Sub Element Description <faultcode> A code for identifying the fault <faultstring> A human readable explanation of the fault <faultfactor> Information about who caused the fault to happen <detail> Holds application specific error information related to the Body element http://grid.rit.edu

  18. Example of SOAP

  19. WSDL • WSDL stands for Web Services Description Language. • WSDL is an XML-based language for describing Web services and how to access them. • WSDL is a document written in XML. The document describes a Web service. It specifies the location of the service and the operations (or methods) the service exposes. http://grid.rit.edu

  20. WSDL Document • <definitions><types>  definition of types........</types><message>  definition of a message....</message><portType>  definition of a port.......</portType><binding>  definition of a binding....</binding></definitions> http://grid.rit.edu

  21. WSDL Ports • The <portType> element is the most important WSDL element. • It describes a web service, the operations that can be performed, and the messages that are involved. • The <portType> element can be compared to a function library (or a module, or a class) in a traditional programming language. http://grid.rit.edu

  22. WSDL Bindings • The <binding> element defines the message format and protocol details for each port. • The binding element has two attributes - name and type. • The name attribute (you can use any name you want) defines the name of the binding, and the type attribute points to the port for the binding. • The soap:binding element has two attributes - style and transport. • The style attribute can be "rpc" or "document". In this case we use document. The transport attribute defines the SOAP protocol to use. In this case we use HTTP. • The operation element defines each operation that the port exposes. • For each operation the corresponding SOAP action has to be defined. You must also specify how the input and output are encoded. In this case we use "literal". http://grid.rit.edu

  23. WSDL Example http://grid.rit.edu

  24. DEMO http://grid.rit.edu

  25. References • www.wikipedia.com • http://www.w3schools.com/ • http://msdn.microsoft.com/en-us/default.aspx http://grid.rit.edu

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