Chapter 5. Web Services

1. Chapter 5. Web Services Introduction Web Service Infrastructure 1

2. 1. Introduction B2B Integration Manual Integration Between Companies B2B interactions occur by accessing Web pages, filling Web forms, or via email. Traditional web-enabled applications are primarily focused on presentation and are unable to interact with other applications. The main reason is that they are built using different web technologies, and their access is limited through an Internet browser or by using an application-specific client. warehouse 2

3. Web Service Paradigm Web Service Overview Web service addresses the challenges faced by traditional systems for B2B integration by bringing a set of new features. • Service-Oriented Architecture • Functionality always exposed as services • Loosely coupled • Invoked by programs as well as users • Redesign of middleware protocols • Peer-to-Peer • Between trust domains • Compatibility with Internet • Standardization •Web standards 3

4. Web Service Overview (ctd.) Web services introduce a new paradigm for enabling the exchange of information across the Internet using a wide range of computing platforms, based on the use of open Internet standards and technologies. Web services are self-describing and modular business applications that expose the business logic as services over the Internet through programmable interfaces and using standard Internet protocols. As such they can be defined as “loosely coupled software components delivered over Internet standard technologies”. Based on XML standards, web services can achieve interoperability of applications based on different programming languages and platforms. This facilitates the delivery of business applications as a service accessible to anyone, anytime, at any location, and using any platform. 4

5. 2. Web Service Infrastructure Basic Web Service Infrastructure Using SOAP  SOAP: XML-based Messaging protocol for exchanging information between the service provider and service requester. To approximate, this is just RPC using XML to encode messages (SOAP) and HTTP to transport them. 5

6. Using WSDL Specification XML schema-based specification for describing Web services as a collection of operations and data input/output parameters as messages. Defines the communication model with a binding mechanism to attach any transport protocol, data format, or structure to an abstract message or operation. Note: all WSDL “processing” happens at Development time. 6

7. Using UDDI Registry A mechanism to register and categorize Web services in a registry that users communicate to in order to discover and locate registered services. A query submitted to the UDDI returns the WSDL description of the service interface. The developer can use this description to construct a SOAP client interface that can communicate with the service provider. Again, this is just RPC with a Directory 7

8. Simple Object Access Protocol • Specifies: • message format for one-way communication • specification for SOAP RPC • rules for processing SOAP messages • rules for transport - HTTP and SMTP A SOAP Message -Consists of the following: SOAPEnvelope: specifies two things: an XML namespace and an encoding style. • SOAP header: used to indicate some additional processing at an intermediate node, that is, processing independent of the processing done at the final destination. • SOAP body: contains the main part of the SOAP message, i.e., the part intended for the final recipient of the SOAP message. 8

9. SOAP Message-Example 9

10. SOAP Communications: Document vs. RPC -SOAP allows Web services communications using either RPC-based synchronous or messaging-based asynchronous communication models. 10

11. SOAP over HTTP -A SOAP message is transported through the network using an existing Internet protocol -HTTP is typically used, although other protocols, e.g., SMTP can be used -The specification of which protocol to use is called a binding. -In addition of specifying the transport mechanism, SOAP bindings also describe implicitly the address of the ultimate SOAP message receiver, e.g., the URL in the case of HTTP and “to” address for SMTP 11

12. Simple Implementation of SOAP 12

13. Example: Flow of web service call using J2EE 13

14. WSDL Specifications XML schema-based specification for describing Web services as a collection of operations and data input/output parameters as messages. Consist of: • Abstract part • signatures, operations • like traditional IDL • Concrete part • bindings/services/ ports Concrete Part • Interface Bindings • message encoding & protocol bindings • Ports • interface binding & network address • Services • logical groupings of ports 14

15. A WSDL Service Specification 15

16. Automatic Generation of WSDL 16

17. Universal Description Discovery and Integration A mechanism to register and categorize Web services in a registry that users communicate to in order to discover and locate registered services. Specifically: • Service Registry • for browsing by developers • for dynamic binding • Business registry • original goal: global registry, every business and exported service registered there • now: support interaction between private and public UDDI registries 17

18. Information in UDDI • Business entity • an organization that provides Web services • Business Service • group of Web Services that cooperate in performing some business process • bindingTemplate • technical information needed to use the service • tModel • general container for a specification 18 Stored in the UDDI registry

19. Model Description and Sharing 19