Web Services

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Web Services
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Agenda

• Introduction
• Technology Overview
• Example Scenario
• Summary
• QA

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Introduction
4
Questions

• What is a web service?
• Why should I use web services?
• How can I use web services?

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Web Services - from different perspectives

• From a business perspective web services is all
  about integration, integrating application
  functionality within an organization or
  integrating application between business
  partners.
• From a technical perspective a web service is a
  collection of one or more related operations that
  are accessible over a network and are described
  by a service description.

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What is a Web Service

• A definition
• A Web service is a business process or step
  within a business process that is made available
  over a network to internal and/or external
  business partners to achieve some business goal

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Web Services
Protocol
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Web Services - What everyone wants

• An easy way to integrate trading partners
• A flexible solution that works in a multi-vendor
  environment
• Easier ways of describing and exchanging
  information
• The ability to operate in multiple verticals and
  to support emerging standards

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Technology Overview
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Major types of Web Services

• Remote Procedure Call (RPC)-oriented
• Sends data formatted as arguments to a procedure
  or object invocation
• Like CORBA, COM, or EJB
• Returns a result directly (synchronous)
• Document-oriented
• Sends data formatted as a business document such
  as a purchase order
• Like MQ Series, MSMQ or JMS
• Typically initiates a process flow (asynchronous)

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RPC-Oriented Web Service
Web Service Interface
Request
Response
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Document-Oriented Web Service
Web Service Interface
Bulk Order
Database
Email acknowledgment
Step 2
Step 3
Invoice
Step 4
Business Process Flow
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Service Oriented Architecture
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Service Oriented Architecture

• Roles
• Service Requestor - use service brokers to
  discover Web services, then invoke those services
  to create applications.
• Service Provider - provides services and maintain
  a registry that makes those services available.
• Service Broker - matches service providers with
  service requestors.
• Operations
• Publish - involves advertising services to a
  registry (publishing) or removing those entries
  (un-publishing). The service provider contacts
  the service broker to publish or un-publish a
  service.
• Find - is performed by service requestors and
  service brokers together. The service requestors
  describe the kinds of services they're looking
  for, and the service brokers deliver the results
  that best match the request.
• Bind - takes place between the service requestor
  and the service provider. The two parties
  negotiate as appropriate so the requestor can
  access and invoke services of the provider.

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Web Services Technologies

• XML (eXtensible Markup Language)
• The root technology for web services, provides a
  common language.
• Version 1.0
• SOAP (Simple Object Access Protocol)
• The XML based communication protocol
• Version 1.2 (latest working draft July 2002)
• WSDL ( Web Services Description Language)
• The web service description API
• Version 1.2 (latest working draft July 2002)
• UDDI (Universal Description, Discovery, and
  Integration)
• The publishing and discovery API for Web Services
• Version 2 implemented today by IBM, Microsoft
  and Software AG

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SOAP

• A lightweight, flexible XML protocol for
• Whole document exchange
• RPC-style interaction
• SOAP is usually http based
• SOAP is completely extensible (transactions,
  security, asynchronous messaging, etc.)
• SOAP can be mapped to other transports

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SOAP Details
Unit of communication
Envelope
Attributes or qualities of the communication
Header
Block Block
Body
Message itself Procedure call parameters or
document
Block Block
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WSDL

• A specific type of XML schema for Web Services
• Roughly equal to IDL
• Defines
• Data Types
• Data exchanged (messages)
• Operations
• Mapping to protocols (http, MIME)
• Services

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WSDL

• Defines services as collections of endpoints or
  ports
• Defines the abstract interfaces of services, and
  the bindings available to access those services
• combines notions of what a service is, and how to
  get to it
• Handles both document-oriented and
  method-oriented services
• Stored in repository or registry

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WSDL Details - Abstract
PortTypes
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WSDL Details - Concrete
Service
Port
Port
Port
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UDDI

• White pages
• address, contact information, business names
• Yellow pages
• categorize the business
• Green pages
• technical info about exposed services, especially
  service definitions

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UDDI

• Repository of business data for the Web
• SOAP APIs for inquiries and publishing
• Contains search and contact information for
  businesses
• Includes references to WSDLs and other Web
  service descriptions
• Work in progress

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UDDI Details
Businesses populate the registry with
descriptions of the services they support
1.
UDDI Business Registry
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Basic Model
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Emerging Web Services Technologies

• Security
• XML Signature and XML Encryption
• SAML (Security Assertion Markup Language) used
  for authentication, authorization and SSO (single
  sign-on)
• WS-Security framework for SOAP security
  interchange
• XKMS (XML Key Management Services) - to be used
  with PKI
• Transactions
• BTP (Business Transaction Protocol)
• Service Level
• WSEL (Web Service Endpoint Language)
• Business Process/Workflow
• XLANG
• WSFL (Web Services Flow Language)

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Web Services Advantages

• Relies on ubiquitous web infrastructure
• Everyone is connected to the Net
• Uses commodity software
• High levels of abstraction
• Maps to any existing technology or platform
• Service-oriented architecture
• Broad industry support
• IBM, Microsoft, Software AG, Sun, Bea,

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Example Scenario
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Scenario
ABC Company
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Scenario

• ABC Company is a supplier of components.
• ABC Company would like to expose one of it
  business processes to its partners, specifically
  they would like to allow their business partners
  to check their inventory before placing an order.
• ABC Company decides to deploy a Java component to
  it application server and then expose it as web
  service.

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Steps

• Building a Web Service
• Accessing a Web Service
• Using a Web Service

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Building Web Services
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Building Web Services

• 1. A Web service provider builds an artifact
  (e.g. a Java bean) that contains the business
  logic and code to access the required back-end
  systems.
• 2. The bean representing the Web service is
  packaged as a archive file for deployment to the
  Application Server.
• 3. The archive file is deployed to the
  application server so the SOAP server servlet can
  find the class and the methods in response to
  incoming SOAP messages requesting this service.
• 4. Once the artifact has been developed that
  represents the logic of the Web service, the
  developer can create a WSDL description of the
  service.
• 5. The description of the Web service is then
  published to the UDDI registry so others can find
  this service.

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Accessing Web Services
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Accessing Web Services

• 1. The application developer begins working on a
  new application.
• 2. The developer can search a UDDI registry for
  an existing Web service that could be used in the
  Web application.
• 3. The developer locates the required Web service
  and downloads a WSDL describing how to bind and
  interact with the Web service.
• 4. The developer generates a client proxy from
  the WSDL.
• 5. The developer codes the calls to the client
  proxy methods in the application.

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Using a Web Service
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Using a Web Services

• 1. The service requestors application uses the
  proxy client to request information.
• 2. The client proxy will serialize the method to
  be invoked on the remote server and the method's
  parameters. Then it will post an HTTP request
  with the SOAP message. When the HTTP request
  arrives at the application server of the service
  provider, the application server forwards it to
  the SOAP servlet.
• 3. The SOAP servlet de-serializes the method and
  its parameters, instantiates the artifact, and
  invokes on it the Web service method that
  contains the Web service functionality.
• 4. The back-end access to a legacy system occurs.
• 5. The results are returned.
• 6. The SOAP servlet returns the results to the
  service requesters client proxy. The proxy
  client de-serializes the results from the SOAP
  message.
• 7. The client proxy returns the results to the
  service requestor's application.

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Summary

• Web services expose existing business processes
  or steps.
• Web services take advantage of the ubiquitous web
  infrastructure.
• Web services are based on open standard backed by
  major players in various industries.

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Resources

• http//www.w3.org/XML/
• http//www.w3.org/2002/ws/
• http//www.w3.org/TR/SOAP/
• http//www.w3.org/TR/wsdl
• http//www.oasis-open.org/
• http//www.uddi.org/
• http//www.ws-i.org/
• http//www.xmethods.org/

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Questions Answers