Web Services (adapted from Erdogan Dogdu's presentation)

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Web Services(adapted from Erdogan Dogdu's
presentation)

• Leonidas Fegaras

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What are Web Services?

• Services available via the Web
• Mostly for application-to-application
  communication
• Enables business-to-business transactions
• Examples
• stock quote service
• weather service
• map service
• Web search service
• Based on XML
• SOAP Simple Object Access Protocol
• WSDL Web Service Description Language
• UDDI Universal Description, Discovery, and
  Integration

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SOAP

• A lightweight protocol for exchanging information
  in a distributed, heterogeneous environment
• Enables cross-platform interoperability
• programming language neutral
• hardware independent
• protocol independent
• Works over existing Internet infrastructure
• Builds on XML standards
• Defines
• message format
• data encoding
• headers for sending messages receiving responses

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WSDL Web Services Description Language

• XML schema for describing Web Services
• Service interface definition
• abstract semantics for Web Service
• Service implementation definition
• concrete end points and network addresses where
  Web Service can be invoked
• Used primarily (although not exclusively) to
  describe SOAP services
• Describes four critical pieces of data
• Interface information describing all publicly
  available functions
• Data type information for all message requests
  and message responses
• Binding information about the transport protocol
  to be used
• Address information for locating the specified
  service

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Main Structure

• ltdefinition namespace http/ gt
• lttypegt xschema types lt/typegt
• ltmessagegt lt/messagegt
• ltportgt a set of operations lt/portgt
• ltbindinggt communication protocols lt/bindinggt
• ltservicegt a list of binding and ports lt/servicegt
• ltdefinitiongt

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WSDL Parts

• lttypesgt define types used in message declaration
• XML Schema must be supported by any vendor of
  WSDL conformant products
• The ltmessagegt element defines the data elements
  of an operation
• each message may consist of one or more parts
• similar to the parameters of a function call in a
  traditional programming language
• The ltportTypegt defines a web service, the
  operations that can be performed, and the
  messages that are involved
• defines the connection point to a web service, an
  instance of ltportTypegt.
• similar to a function library in a traditional
  programming language
• each operation can be compared to a function in a
  traditional programming language

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Example HelloService.wsdl

• lt?xml version"1.0" encoding"UTF-8"?gt
• ltdefinitions name"HelloService"
• targetNamespace"http//www.ecerami.com/wsdl/He
  lloService.wsdl"
• xmlns"http//schemas.xmlsoap.org/wsdl/"
• xmlnssoap"http//schemas.xmlsoap.org/wsdl/soa
  p/"
• xmlnstns"http//www.ecerami.com/wsdl/HelloSer
  vice.wsdl"
• xmlnsxsd"http//www.w3.org/2001/XMLSchema"gt
• ltmessage name"SayHelloRequest"gt
• ltpart name"firstName" type"xsdstring"/gt
• lt/messagegt
• ltmessage name"SayHelloResponse"gt
• ltpart name"greeting" type"xsdstring"/gt
• lt/messagegt
• ltportType name"Hello_PortType"gt
• ltoperation name"sayHello"gt
• ltinput message"tnsSayHelloRequest"/gt
• ltoutput message"tnsSayHelloResponse"/gt
• lt/operationgt
• lt/portTypegt

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Example (cont.)

• ltbinding name"Hello_Binding" type"tnsHello_Port
  Type"gt
• ltsoapbinding style"rpc"
• transport"http//schemas.xmlsoap.org/soa
  p/http"/gt
• ltoperation name"sayHello"gt
• ltsoapoperation soapAction"sayHello"/gt
• ltinputgt
• ltsoapbody
• encodingStyle"http//schemas.xmlso
  ap.org/soap/encoding/"
• namespace"urnexampleshelloservic
  e"
• use"encoded"/gt
• lt/inputgt
• ltoutputgt
• ltsoapbody
• encodingStyle"http//schemas.xmlso
  ap.org/soap/encoding/"
• namespace"urnexampleshelloservic
  e"
• use"encoded"/gt
• lt/outputgt
• lt/operationgt
• lt/bindinggt

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Example (cont.)

• ltservice name"Hello_Service"gt
• ltdocumentationgtWSDL File for
  HelloServicelt/documentationgt
• ltport binding"tnsHello_Binding"
  name"Hello_Port"gt
• ltsoapaddress
• location"http//localhost8080/soap/s
  ervlet/rpcrouter"/gt
• lt/portgt
• lt/servicegt
• lt/definitionsgt

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WSDL Invocation Tools

• You can use any SOAP method to call HelloService
• Using the GLUE tool
• invoke URL method arg1 arg2 arg3...
• To invoke the HelloService with GLUE
• place the HelloService.wsdl file within a
  publicly available directory
• issue the command
• invoke http//localhost8080/wsdl/HelloService.wsd
  l sayHello World
• GLUE will
• download the specified WSDL file
• invoke the sayHello method
• pass World as a parameter
• Server response
• result Hello, World!

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UDDI

• UDDI Universal Description, Discovery, and
  Integration
• Industry initiative to address discovery
• a registration database for Web Services
• Specifications
• schema for service providers and descriptions
• API for publishing and searching
• developed on industry standards (XML, HTTP,
  TCP/IP, SOAP)
• applies to both XML and non-XML services
• Implementation
• public and private instances of specification

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Providers, Services and Bindings

• Providers
• Examples Accounting Department, Corporate
  Application Server
• Name, Description, Contact Information
• Categorization and Identification Information
• Services
• Examples Purchase Order services, Payroll
  services
• Name, Description(s)
• Categorization Information
• Bindings
• Description(s), access points, parameters
• Examples Access Point (http//...) for Web
  Service

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Features

• Neutral in terms of protocols
• as a registry, it can contain pointers to
  anything
• Can search by business, service, Web Service,
  binding
• Usage of Globally Unique Identifiers (GUIDs)
• Specification allows public and private nodes
• Delineation between interface and implementation

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tModel

• lttModelgt represents meta-data and interfaces

lttModel xmlns"urnuddi-orgapi"
tModelKey"UUIDAAAAAAAA-AAAA-AAAA-AAAA-AAAAAAAAAA
AA"gt ltnamegtmicrosoft-comcreditchecklt/namegt
ltdescription xmllang"en"gtCheck credit
limitslt/descriptiongt ltoverviewDocgt
ltoverviewURLgthttp//schema.com/creditcheck.wsdl
lt/overviewURLgt lt/overviewDocgt
ltcategoryBaggt ltkeyedReference
tModelKey"UUIDCD153257-086A-4237-B336-6BDCBDCC66
34" keyName"Consumer credit gathering or
reporting services" keyValue"84.14.16.01.0
0"/gt ltkeyedReference
tModelKey"UUIDC1ACF26D-9672-4404-9D70-39B756E62A
B4" keyName"types" keyValue"wsdlSpec"/gt
lt/categoryBaggt lt/tModelgt
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bindingTemplate

• A bindingTemplate represents data and
  implementation details

ltbindingTemplate serviceKey"33c3d124-e967-4ab1-8f
51-d93d95fac91a" bindingKey"48f2bc6b-a6de-4be8-9f
2b-2342aeafaaac"gt ltaccessPoint
URLType"http"gt http//localhost/HelloWorld/Serv
ice1.asmx lt/accessPointgt lttModelInstanceDetail
sgt lttModelInstanceInfo tModelKey"uuid64c7
56d1-3374-4e00-ae83-ee12e38fae63/gt
lt/tModelInstanceDetailsgt lt/bindingTemplategt