webservices.ppt for website designing ppt
- 1. Web Services and SOA CS 237
- 2. Web Services - Definition from W3C “ A Web service is a software system identified by a URI, 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 in a manner prescribed by its definition, using XML based messages conveyed by internet protocols.”
- 3. Service Oriented Architectures Technologies capable of: •Exchanging messages •Describing Web services •Publishing and discovering Web service descriptions Component Role Operation service requestor retrieves a service description A service publishes its description One-way, conversational, many-to-many
- 4. Web Services – Architectural Extensions – Incorporates additional features and functionality by extending technologies and components defined within the basic architecture, such as: • Asynchronous messaging • Attachment – typical usage : associating binary data with SOAP messages. • Caching • Message exchange pattern (MEP) - Describes a generalized pattern of message exchange between two services. e.g. : one-way, request/response, publish/subscribe, and broadcast. • Reliable message - implementation of Reliable Messaging one MEP is a series of requests between two nodes with an acknowledgement SOAP Module. • Message confidentiality – Can transmit the message via SSL or TLS, or have a SOAP Module provides for encryption and decryption. • Message integrity – Can have a SOAP Module use digital signature. • Session
- 5. The Complete Web Services "Stack" More mature technologie s
- 6. The Wire Stack •Transport: HTTP is the de facto, other may be supported. •Packaging: SOAP is the de facto standard for XML messaging. •Extensions : Additional information attached to web services messages.
- 7. The Description Stack It is actually a stack of description documents defined using XML Schema. Satisfied by WSDL minimum service description necessary to support interoperable Web services. facts, or assertions, and rules that apply to a particular Web service Input/ Output rendering Not fully specified
- 8. The Discovery Stack Service can be published using a variety of mechanisms: Direct publish: description sent directly to requestor; WSIL : HTTP GET retrieves descriptions from URL; Universal Description, Discovery and Integration (UDDI) registries: a Web-based distributed directory. Service requestors can retrieve a service description at design time (search by interface) or runtime (by communication and QoS) from a Web page (URL), a service description repository, a simple service registry or a UDDI registry. Discovery depends on how services are published; WSIL : de-centralized service discovery method
- 9. The technology so far The WS technology is completely based on XML. Therefore, both the data format and the interaction protocols are XML-based: customized XML -> data format SOAP -> communication protocol WSDL -> the Interface definition language WSIL/UDDI -> standards for services discovery The lowest-level layers (the transport layer) should exploit some existing Internet protocols, like HTTP or SMTP
- 10. What is XML XML is a simple tag-based language for describing information in a structured way. Basic elements: Tags Attributes Text <xhtml:table><xhtml:tr> <xhtml:td width="40%">LastName</xhtml:td> <xhtml:td width="60%">Allen</xhtml:td> </xhtml:tr></xhtml:table> StartTag Text EndTag Attributes LastName Allen
- 11. How to work on XML The tree-like structure of XML makes developers life hard. In practice there is not a standard way for editing and analyzing, but the best method depends on your need. Just choose among: SAX -> callback-based parser DOM -> tree representation XSLT -> “XML to XML” conversion XPATH -> queries XML Binding -> transparent conversion to objects
- 12. Simple Object Access Protocol SOAP is a technology to support the exchange of XML-coded messages over a transport protocol, such as HTTP and SMTP. (wire stack) HTTP server Skeleton Server HTTP client Stub Client XML XML POST… HTTP 1.1 200 OK SOAP SOAP HTTP SOAP XML Protocols Folding SOAP basic mechanism
- 13. Simple Object Access Protocol A SOAP runtime engine basically adds a XML envelope to an existing XML document SOAP Envelope XML Document <soap:Envelope> <soap:Header> <axis:SessionKey> SDHH37TYEW7R7 </axis:SessionKey> </soap:Header> <soap:Body> <GetPrice> <Item>Apples</Item> </GetPrice> </soap:Body> </soap:Envelope> SOAP Body SOAP Header Communicatio n Info Example Document Container Session, Authentication, Routing, Security
- 14. SOAP Encoding Dealing directly with XML messages is not easy. Therefore, SOAP provides a “RPC emulation” technology The result: developers work with web services like with traditional RPC (e.g. CORBA,DCOM,DCE) The “RPC emulation” is named SOAP encoding. Fundamentally it is a set of rules to map a procedure invocation to a XML document.
- 15. SOAP Encoding The rules: method name -> first level element in the SOAP Body arguments identifiers -> second level elements arguments values -> third level elements arguments types -> attribute xsi:type ClockService.getTime(location="USA"); <soap:Body> <getTime> <location xsi:type="xsd:string">USA</path> </getTime> </soap:Body> Service Request
- 16. Web Service Description Language WSDL is a standard format to describe a Web Service (description stack) A WSDL document is composed by two sections: An abstract interface section -> like in traditional IDL, it defines the signatures of procedures (RPC-style) or messages (document-style) A deployment section -> it defines the service location and the supported transport protocols Fundamentally a client uses the WSDL to create the stub or to dinamically decode messages.
- 17. Web Service Introspection Language WSIL and UDDI are the standard way to search Web Services. (Discovery stack) WSIL is the decentralized approach. Fundamentally a WSIL document contains a directory of the Web Services deployed on a server. It is anologous to the index.html document for web pages. In the future, specific crawlers will browse the Internet looking for WSIL documents, like Google does today for web pages.
- 18. Web Service Introspection Language <inspection> <abstract>Acme Industries Public Web Services</abstract> <service> <name>Store Finder Service</name> <abstract> A service to perform a geographical search of Acme stores. </abstract> <description location="http://example.org/services/storefinder.wsdl"/> </service> <link location="http://example.org/services/ecommerce.wsil"/> </inspection> Service name Service location and description Link to an other WSIL page
- 19. UDDI UDDI is a complimentary approach for searching based on a centralized repository. The repository is an “electronic yellow pages” for firms that offer web services online. Besides the names of services and their WSDL descriptors, firms can add a description of their business, phone numbers, addresses... UDDI repositories are offered by many agencies - e.g. IBM, Microsoft and HP.
- 20. References J2EE: A platform of choice for Web Services. http://www.sun.it/eventi/codecamps_2002/pdf/j2ee_a_platfor m_of_choice_for_web_services.pdf XML in J2EE Platform. http://www.sun.it/eventi/codecamps_2002/pdf/xml_in_j2ee_p latform.pdf A Busy Developers Guide to WSDL 1.1 http://radio.weblogs.com/0101679/stories/2002/02/15/aBusy DevelopersGuideToWsdl11.html A Busy Developer's Guide to SOAP 1.1 . http://www.soapware.org/bdg A Young Person's Guide to The Simple Object Access Protocol. http://msdn.microsoft.com/msdnmag/issues/0300/soap/soap. asp An XML Overview Towards Understanding SOAP. http://msdn.microsoft.com/library/en-us/dnwebsrv/html/xmlo verchap2.asp
- 21. References Deploying Web Services on Java 2, Enterprise Edition. http://developer.java.sun.com/developer/technicalArticles/We bServices/wsj2ee/ The Python Web services developer. http://www- 106.ibm.com/developerworks/webservices/library/ws- pyth1.html Understanding WSDL in a UDDI registry. http://www- 106.ibm.com/developerworks/webservices/library/ws-wsdl/ Dot-com builder overview of WSDL. http://dcb.sun.com/practices/webservices/overviews/overview _wsdl.jsp Getting Started with JAX-RPC. http://developer.java.sun.com/developer/technicalArticles/We bServices/getstartjaxrpc/ Introduction to WSDL. http://www.devxpert.com/tutors/wsdl/wsdl.asp
- 22. References Integrating SOAP into ebXML. http://www.itworld.com/AppDev/1472/ITW010404ebXML/ Top ten FAQs for Web Services. http://www.oreillynet.com/pub/a/webservices/2002/02/12/web servicefaqs.html Web Services Introduction. http://www.perfectxml.com/WebSvc1.asp SOAP archives. http://www.soap.org/archive.iphtml SOAP Introduction. http://www.w3schools.com/soap/soap_intro.asp Web Services Description Language (WSDL) Explained. http://msdn.microsoft.com/library/en-us/dnwebsrv/html/wsdle xplained.asp WSDL Interop Adventures. http://www.byte.com/documents/s=7031/byt1015007393289/ 0304_udell.html Java Web Services Tutorial. http://java.sun.com/webservices/docs/1.0/tutorial/doc/JavaWS TutorialTOC.html
Editor's Notes
- #2: Our definition of the term "Web services" does not presuppose the use of SOAP as a packaging format or a processing model. Nor does it presuppose the use of WSDL as a service description language. There are, and will be in the future, plenty of Web services that use raw HTTP as a data transfer protocol and some mutually agreed-upon XML format as the message content. The Web Services *reference architecture* does, however, assume that the higher levels of the Web services protocol stack are built on the foundation of SOAP and WSDL.
- #3: Components The Service: Whereas a web service is an interface described by a service description, its implementation is the service. A service is a software module deployed on network accessible platforms provided by the service provider. It exists to be invoked by or to interact with a service requestor. It may also function as a requestor, using other web services in its implementation. The Service Description: The service description contains the details of the interface and implementation of the service. This includes its data types, operations, binding information, and network location. It could also include categorization and other meta data to facilitate discovery and utilization by requestors. The complete description may be realized as a set of XML description documents. The service description may be published to a requestor directly or to a discovery agency. Publish: In order to be accessible, a service needs to publish its description such that the requestor can subsequently find it. Where it is published can vary depending upon the requirements of the application (see Service Publication Stack discussion for more details) Find: In the find operation, the service requestor retrieves a service description directly or queries the registry for the type of service required (see Service Discovery for more details). The find operation may be involved in two different lifecycle phases for the service requestor: at design time in order to retrieve the service's interface description for program development, and at runtime in order to retrieve the service's binding and location description for invocation. Interact: Eventually, a service needs to be invoked. In the interact operation the service requestor invokes or initiates an interaction with the service at runtime using the binding details in the service description to locate, contact, and invoke the service. Examples of the interaction include: single message one way, broadcast from requester to many services, a multi message conversation, or a business process. Any of these types of interactions can be synchronous or asynchronous.
- #5: Independent stacks assembled into a single stack where each additional layer builds upon the capabilities provided by those below it. The vertical towers represent the variety of over arching concerns that must be addressed at every level of each of the stacks.
- #6: Transport : Because of its ubiquity, HTTP is the de facto standard network protocol for Internet-available web services. Other Internet protocols may be supported including SMTP and FTP. Packaging : Packaging, represents the technologies that may be used to package information being exchanged. XML has been broadly adopted as the basis for Web service message packaging protocols and SOAP is currently the de facto standard for XML messaging. Extensions : Provides a framework that allows additional information to be attached to Web service messages representing a variety of additional concerns; such as context, routing, policy, etc. SOAP defines a mechanism to incorporate orthogonal extensions (also known as features) to the message in the form of headers and encoding rules.
- #7: WSDL is an XML document format for describing Web services as a set of endpoints operating on messages containing either document-oriented or procedure-oriented (RPC) messages. The operations and messages are described abstractly, and then bound to a concrete network protocol and message format to define an endpoint. Related concrete endpoints may be combined into services. Interface Description maps to the Abstract interface in WSDL, explained later. Implementation Description maps to the Deployment section in WSDL, explained later. Policy would be used to describe or point to documents describing the owning business, associated products, keywords, taxonomies for the service, security policies, quality of service attributes, etc. Policy may be used by the over-arching concerns: security, quality of service, and management; as well as higher layers of the description stack. The composition and orchestration layers describe how service-to-service communications, collaborations, and flows are performed.