Webservices
- 1. Web Services: Web Services can convert your application into a Web-application, which can publish its function or message to the rest of the world. The basic Web Services platform is XML + HTTP. Web Services can convert your applications into Web- applications. Web Services are published, found, and used through the Web. What You Should Already Know Before you continue, you should have a basic understanding of the following: HTML XML 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 Web services can be used by other applications XML is the basis for Web services How Does it Work? 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.
- 2. Web services platform elements: SOAP (Simple Object Access Protocol) UDDI (Universal Description, Discovery and Integration) WSDL (Web Services Description Language) Web Services have Two Types of Uses Reusable application-components. There are things applications need very often. So why make these over and over again? Web services can offer application-components like: currency conversion, weather reports, or even language translation as services. Connect existing software. Web services can help to solve the interoperability problem by giving different applications a way to link their data. With Web services you can exchange data between different applications and different platforms. Web Services have three basic platform elements: SOAP, WSDL and UDDI. Web Services have three basic platform elements: SOAP, WSDL and UDDI. What is SOAP? SOAP is an XML-based protocol to let applications exchange information over HTTP. Or more simple: SOAP is a protocol for accessing a Web Service. SOAP stands for Simple Object Access Protocol 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 SOAP is simple and extensible SOAP allows you to get around firewalls SOAP is a W3C standard Read more about SOAP on our Home page.
- 3. What is WSDL? WSDL is an XML-based language for locating and describing Web services. WSDL stands for Web Services Description Language WSDL is based on XML WSDL is used to describe Web services WSDL is used to locate Web services WSDL is a W3C standard Read more about WSDL on our Home page. What is UDDI? UDDI is a directory service where companies can register and search for Web services. UDDI stands for Universal Description, Discovery and Integration 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 Read more about UDDI in our WSDL Tutorial. Any application can have a Web Service component. Web Services can be created regardless of programming language. Web Services Summary This tutorial has taught you how to convert your applications into web-applications. You have learned how to use XML to send messages between applications. You have also learned how to export a function (create a web service) from your application. Now You Know Web Services, What's Next? The next step is to learn about WSDL and SOAP. WSDL WSDL is an XML-based language for describing Web services and how to access them.
- 4. WSDL describes a web service, along with the message format and protocol details for the web service. If you want to learn more about WSDL, please visit our WSDL tutorial. SOAP SOAP is a simple XML-based protocol that allows applications to exchange information over HTTP. Or more simply: SOAP is a protocol for accessing a web service. If you want to learn more about SOAP, please visit our SOAP tutorial. WSDL (Web Services Description Language) is an XML-based language for describing Web services and how to access them WSDL is an XML-based language for describing Web services and how to access them. What You Should Already Know Before you continue you should have a basic understanding of the following: XML XML Namespaces XML Schema If you want to study these subjects first, find the tutorials on our Home page. What is WSDL? WSDL stands for Web Services Description Language WSDL is written in XML WSDL is an XML document WSDL is used to describe Web services WSDL is also used to locate Web services WSDL is a W3C recommendation WSDL Describes Web Services WSDL stands for Web Services Description Language. 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. WSDL document is just a simple XML document.
- 5. It contains set of definitions to describe a web service. The WSDL Document Structure A WSDL document describes a web service using these major elements: Element Defines <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 service The main structure of a WSDL document looks like this: <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> A WSDL document can also contain other elements, like extension elements, and a service element that makes it possible to group together the definitions of several web services in one single WSDL document. 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. WSDL Messages
- 6. The <message> element defines the data elements of an operation. Each message can consist of one or more parts. The parts can be compared to the parameters of a function call in a traditional programming language. WSDL Types The <types> element defines the data types that are used by the web service. For maximum platform neutrality, WSDL uses XML Schema syntax to define data types. WSDL Bindings The <binding> element defines the message format and protocol details for each port. WSDL Example This is a simplified fraction of a WSDL document: <message name="getTermRequest"> <part name="term" type="xs:string"/> </message> <message name="getTermResponse"> <part name="value" type="xs:string"/> </message> <portType name="glossaryTerms"> <operation name="getTerm"> <input message="getTermRequest"/> <output message="getTermResponse"/> </operation> </portType> In this example the <portType> element defines "glossaryTerms" as the name of a port, and "getTerm" as the name of an operation. The "getTerm" operation has an input message called "getTermRequest" and an output message called "getTermResponse". The <message> elements define the parts of each message and the associated data types. Compared to traditional programming, glossaryTerms is a function library, "getTerm" is a function with "getTermRequest" as the input parameter, and getTermResponse as the return parameter.
- 7. A WSDL port describes the interfaces (legal operations) exposed by a web service. WSDL Ports The <portType> element is the most important WSDL element. It defines a web service, the operations that can be performed, and the messages that are involved. The port defines the connection point to a web service. It can be compared to a function library (or a module, or a class) in a traditional programming language. Each operation can be compared to a function in a traditional programming language. Operation Types The request-response type is the most common operation type, but WSDL defines four types: Type Definition One-way The operation can receive a message but will not return a response Request-response The operation can receive a request and will return a response Solicit-response The operation can send a request and will wait for a response Notification The operation can send a message but will not wait for a response One-Way Operation A one-way operation example: <message name="newTermValues"> <part name="term" type="xs:string"/> <part name="value" type="xs:string"/> </message> <portType name="glossaryTerms"> <operation name="setTerm"> <input name="newTerm" message="newTermValues"/> </operation> </portType > In the example above, the port "glossaryTerms" defines a one-way operation called "setTerm". The "setTerm" operation allows input of new glossary terms messages using a "newTermValues" message with the input parameters "term" and "value". However, no output is defined for the operation. Request-Response Operation
- 8. A request-response operation example: <message name="getTermRequest"> <part name="term" type="xs:string"/> </message> <message name="getTermResponse"> <part name="value" type="xs:string"/> </message> <portType name="glossaryTerms"> <operation name="getTerm"> <input message="getTermRequest"/> <output message="getTermResponse"/> </operation> </portType> In the example above, the port "glossaryTerms" defines a request-response operation called "getTerm". The "getTerm" operation requires an input message called "getTermRequest" with a parameter called "term", and will return an output message called "getTermResponse" with a parameter ca lled "value". 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, in this case the "glossaryTerms" port. 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". Universal Description, Discovery and Integration (UDDI) is a directory service where businesses can register and search for Web services. What is UDDI
- 9. UDDI is a platform-independent framework for describing services, discovering businesses, and integrating business services by using the Internet. UDDI stands for Universal Description, Discovery and Integration 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 What is UDDI Based On? UDDI uses World Wide Web Consortium (W3C) and Internet Engineering Task Force (IETF) Internet standards such as XML, HTTP, and DNS protocols. UDDI uses WSDL to describe interfaces to web services Additionally, cross platform programming features are addressed by adopting SOAP, known as XML Protocol messaging specifications found at the W3C Web site. UDDI Benefits Any industry or businesses of all sizes can benefit from UDDI. Before UDDI, there was no Internet standard for businesses to reach their customers and partners with information about their products and services. Nor was there a method of how to integrate into each other's systems and processes. Problems the UDDI specification can help to solve: Making it possible to discover the right business from the millions currently online Defining how to enable commerce once the preferred business is discovered Reaching new customers and increasing access to current customers Expanding offerings and extending market reach Solving customer-driven need to remove barriers to allow for rapid participation in the global Internet economy Describing services and business processes programmatically in a single, open, and secure environment How can UDDI be Used If the industry published an UDDI standard for flight rate checking and reservation, airlines could register their services into an UDDI directory. Travel agencies could then search the UDDI directory to find the airline's reservation interface. When the interface is found, the travel agency can communicate with the service immediately because it uses a well-defined reservation interface. Who is Supporting UDDI? UDDI is a cross-industry effort driven by all major platform and software providers like Dell, Fujitsu, HP, Hitachi, IBM, Intel, Microsoft, Oracle, SAP, and Sun, as well as a large community of marketplace operators, and e-business leaders. Over 220 companies are members of the UDDI community.
- 10. SOAP Tutorial SOAP is a simple XML-based protocol to let applications exchange information over HTTP. In our SOAP tutorial, you will learn what SOAP is, and how it uses XML to exchange information between applications. SOAP is a simple XML-based protocolto let applications exchange information over HTTP. Or more simply: SOAP is a protocolfor accessing a Web Service. What You Should Already Know Before you study SOAP you should have a basic understanding of XML and XML Namespaces. If you want to study these subjects first, please read our XML Tutorial. What is SOAP? SOAP stands for Simple Object Access Protocol SOAP is a communication protocol SOAP is for communication between applications SOAP is a format for sending messages SOAP communicates via Internet SOAP is platform independent SOAP is language independent SOAP is based on XML SOAP is simple and extensible SOAP allows you to get around firewalls SOAP is a W3C recommendation 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 Syntax Rules Here are some important syntax rules:
- 11. A SOAP message MUST be encoded using XML A SOAP message MUST use the SOAP Envelope namespace A SOAP message MUST use the SOAP Encoding namespace A SOAP message must NOT contain a DTD reference A SOAP message must NOT contain XML Processing Instructions The SOAP Envelope element is the root element of a SOAP message. The SOAP Envelope Element The required SOAP Envelope element is the root element of a SOAP message. This element defines the XML document as a SOAP message. Example <?xml version="1.0"?> <soap:Envelope xmlns:soap="http://www.w3.org/2001/12/soap-envelope" soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding"> ... Message information goes here ... </soap:Envelope>