18 Copyright © 2005, Oracle. All rights reserved. Distributing Modular Applications: Introduction to Web Services

18-2 Copyright © 2005, Oracle. All rights reserved. Objectives After completing this lesson, you should be able to do the following: Describe the Web services technology Identify the standards used by Web services Identify the benefits of Web services Distinguish between remote procedure call (RPC)- style and document-style Web services Discuss the role of Simple Object Access Protocol (SOAP), Web Services Description Language (WSDL), and Universal Description, Discovery, and Integration (UDDI) in Web services

18-3 Copyright © 2005, Oracle. All rights reserved. What Is a Web Service? External applications HTML XML Web presentation Business logic Web service Databases Application Server HTTP client

18-4 Copyright © 2005, Oracle. All rights reserved. Web Service A Web service is: A software component whose technology is based on a set of standards for building interoperable distributed applications A set of self-describing business functions Service oriented Component based

18-5 Copyright © 2005, Oracle. All rights reserved.

18-6 Copyright © 2005, Oracle. All rights reserved. Service-Oriented Architecture Invoke Service requestor Publish Find Service provider Service registry

18-7 Copyright © 2005, Oracle. All rights reserved. Web Services Constituents Internet for communication XML as universal data format SOAP for XML messaging WSDL for describing the service UDDI for publishing the Web services

18-8 Copyright © 2005, Oracle. All rights reserved.

18-9 Copyright © 2005, Oracle. All rights reserved. Benefits of Web Services Distributed component model with interoperability XML format for representing data. The request and response messages are in the XML format. Programming language independent Easily accessible with standard protocols such as HTTP, HTTPS, SMTP, and FTP Communication through firewalls Existing components can be exposed as Web services to save development time. Different communication styles: –RPC style (synchronous) –Message style (asynchronous)

18-10 Copyright © 2005, Oracle. All rights reserved.

18-11 Copyright © 2005, Oracle. All rights reserved. Web Services Model Web services directory (UDDI) XML interface (WSDL) Web service Find InvokePublish XML interface (WSDL) Client application

18-12 Copyright © 2005, Oracle. All rights reserved. RPC-Style Web Services RPC-style Web services are loosely coupled. SOAP messages model the call and response semantics. This style of communication can be described in WSDL.

18-13 Copyright © 2005, Oracle. All rights reserved. Document-Style Web Services Document-style Web services are loosely coupled. SOAP messages carry arbitrary XML documents. This style of communication can be described in WSDL.

18-14 Copyright © 2005, Oracle. All rights reserved. Oracle Support for Web Services Oracle Application Server 10g is the infrastructure for: Describing Web services Deploying Web services Publishing Web services Invoking Web services Oracle JDeveloper 10g provides tools for: Developing, deploying, publishing, and invoking Web services Modeling, testing, and debugging Web services Browsing UDDI registry to locate Web services Generating stub files to consume Web services

18-15 Copyright © 2005, Oracle. All rights reserved. SOAP: XML Messaging for Web Services Introduces a self-describing data representation format in XML Represents request and response as XML messages Supports both RPC-style and document-style invocation Uses HTTP and other protocols at transport layer Supports data encoding and literal styles SOAP hides details of implementations; works with: –Any programming language –Any operating system –Any hardware platform

18-16 Copyright © 2005, Oracle. All rights reserved. Communication with SOAP Communication by using SOAP protocol includes: Requests to invoke a service Responses from service method Fault from a service SOAP client Request Web server Firewall Response

18-17 Copyright © 2005, Oracle. All rights reserved. SOAP Messages A SOAP message is an XML document that consists of: A mandatory envelope as a top- level element An optional header A mandatory body An optional fault HTTP headers Headers Message name, data, and fault element SOAP envelope SOAP header SOAP body

18-18 Copyright © 2005, Oracle. All rights reserved.

18-19 Copyright © 2005, Oracle. All rights reserved. Web Services Description Language (WSDL) Is a description language to define Web service interfaces and how to invoke them Is an XML Schema for describing Web services: –Service interface definition: Describes what message must be sent and what message is returned –Service implementation definition: Describes to which address the message must be sent Allows both the messages and the operations on the messages to be defined abstractly in XML Answers three key questions about a Web service: –What does a service do? –How is a service accessed? –Where is a service located?

18-20 Copyright © 2005, Oracle. All rights reserved. WSDL <definitions name=Hello... targetNamespace=

18-21 Copyright © 2005, Oracle. All rights reserved.

18-22 Copyright © 2005, Oracle. All rights reserved. UDDI Registry Is an online electronic registry for registering businesses and Web services Is a specification for description and discovery Supports the Publishing and Inquiry APIs to publish and inquire about a Web service

18-23 Copyright © 2005, Oracle. All rights reserved.

18-24 Copyright © 2005, Oracle. All rights reserved. How UDDI Is Used UDDI Business Registry Business portals and marketplaces Business userSoftware developer UDDI Registry Business descriptions Service types

18-25 Copyright © 2005, Oracle. All rights reserved. Searching for a Web Service by Using UDDI Provider info Contact Info Directory of names White pages Yellow pages Search using context such as location, service type. Point to White pages for details. Green pages Information about business model Technical details of provided service Information on business process

18-26 Copyright © 2005, Oracle. All rights reserved. UDDI Specification UDDI Programmers API UDDI Data Structure Specification and XML Schema UDDI Replication Specification and UDDI XML Replication Schema UDDI Operators Specification

18-27 Copyright © 2005, Oracle. All rights reserved. tModel Provides metadata information about a Web service specification Contains references to the specification locations Is used for compliance check

18-28 Copyright © 2005, Oracle. All rights reserved. <tModel tModelKey="uuid: A F-A4B BA78" operator=… authorizedName=…> Airport Weather Web Service to check weather on intl. airports … tModel

18-29 Copyright © 2005, Oracle. All rights reserved.

18-30 Copyright © 2005, Oracle. All rights reserved.

18-31 Copyright © 2005, Oracle. All rights reserved. UDDI Support in Oracle JDeveloper 10g JDeveloper provides a UDDI browser with which you can: Define a connection to a UDDI registry instance Search for services: –Look up tModel by name or category –Locate a service implementing this tModel –Add a business providing this service to the UDDI browser For the located service: –Generate Web service stub/skeleton –View WSDL –View a business that provides the service

18-32 Copyright © 2005, Oracle. All rights reserved. UDDI Browsing with Oracle JDeveloper 10g

18-33 Copyright © 2005, Oracle. All rights reserved. UDDI Publishing and Browsing with Oracle Enterprise Manager Using Oracle Enterprise Manager Application Server Control Console, you can: Browse and register services within the UDDI registry Publish Web services and deploy them to a J2EE container Monitor and administer Web services

18-34 Copyright © 2005, Oracle. All rights reserved. Utilizing External Web Services from JDeveloper

18-35 Copyright © 2005, Oracle. All rights reserved. Summary In this lesson, you should have learned how to: Provide an overview of Web services technology Identify the standards used by Web services Identify the benefits of Web services Locate and invoke Web services by using SOAP, WSDL, and UDDI Distinguish between RPC-style and Document- style Web service

18-36 Copyright © 2005, Oracle. All rights reserved. Practice 18-1: Overview This practice covers revision questions on Web services technology and standards such as SOAP, WSDL, and UDDI.

18-37 Copyright © 2005, Oracle. All rights reserved.

18-38 Copyright © 2005, Oracle. All rights reserved.