WSDL Web Service Description Language

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WSDL Web Service Description Language
www.eu-egee.org
EGEE is a project funded by the European Union
under contract IST-2003-508833
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Objectives

• The role of WSDL
• The structure of a WSDL document
• types
• message
• portType
• binding
• service

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What is the function of WSDL

• WSDL represents a contract between the consumer
  and provider of a service.
• It should guarantee a service format.

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The function of WSDL

• WSDL describes a services exposed interface
• It is what a client sees of your service
• WSDL includes information about
• The data types it uses
• Parameters it requires and returns
• Groupings of functionality
• The protocol to be used to access the service
• The location or address of the service

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WSDL Structure

• A WSDL document is an XML document

lt?xml version"1.0" encoding"UTF-8"?gtltdefinition
sgt lttypesgt lt! define the types here using
XML Schema ? lt/typesgt ltmessagegt lt! XML
messages the web service uses are defined here ?
lt/messagegt ltportTypegt lt! define the input
and output parameters here -? lt/portTypegt
ltbindinggt lt! define the network protocol here
? lt/bindinggt ltservicegt lt! location of the
service ? lt/servicegtlt/definitionsgt
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Referencing between sections
Each section refers to elements defined in other
sections
lt?xml version"1.0" encoding"UTF-8"?gtltdefinition
sgt lttypesgt lt! define the data types here
using XML Schema ? lt/typesgt ltmessagegt lt!
The message will refer to the types defined above
? lt/messagegt ltportTypegt lt! The operations
refer to the messages defined above -?
lt/portTypegt ltbindinggt lt! A binding refers to
a portType defined above ? lt/bindinggt
ltservicegt lt! The service refers to a particular
binding defined above ? lt/servicegtlt/definition
sgt
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Simplified definitions
Each defines things referenced by other sections
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ltimportgt element

• ltdefinitions
• targetNamespaceurn3950
• xmlns http//schema.xmlsoap.org/wsdl/
• xmlnsxsd http//www.w3c.org/2001/XMLSchema
• xmlnssoap http//schemas.xmlsoap.org/wsdl/soap
  /
• xmlnssoapenc http//schemas.xmlsoap.org/soap/em
  coding/
• xmlnstns urn3950gt
• ltimport namespace http//nesc.ac.uk location
  http//nesc.ac.uk/ez.xsd/gt

Acts like C/C include , or Java import.
Incorporates external namespaces
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Namespaces

• WSDL uses a number of different namespaces
  including
• XML Schema Namespaces
• http//www.w3.org/2000/10/XMLSchema
• http//www.w3c.org/2001/XML-Schema-instance
• WSDL Namespaces
• http//schemas.xmlsoap.org/wsdl/soap/
• http//schemas.xmlsoap.org/wsdl/
• SOAP Namespaces
• http//schemas.xmlsoap.org/soap/encoding
• http//schemas.xmlsoap.org/soap/envelope

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The lttypesgt

• The types element contains XML Schemas defining
  the datatypes that are to be passed to and from
  the web service

lttypesgt ltschema targetNamespace"http//example.c
om/stockquote.xsd" xmlns"http//www.w3.org/2000/
10/XMLSchema"gt ltelement name"TradePriceRequest"
gt ltcomplexTypegt ltallgtltelement
name"tickerSymbol" type"string"/gtlt/allgt
lt/complexTypegt lt/elementgt ltelement
name"TradePrice"gt ltcomplexTypegt
ltallgtltelement name"price" type"float"/gtlt/allgt
lt/complexTypegt lt/elementgt lt/schemagt
lt/typesgt
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The ltmessagegt

• The ltmessagegt element is used to define the
  messages that will be exchanged between the
  client and the service
• These message elements contain ltpartgt elements,
  which will be using types defined in the types
  element
• All the parts are namespace qualified

ltmessage name"GetLastTradePriceInput"gt ltpart
name"body" element"xsd1TradePriceRequest"/gt
lt/messagegt ltmessage name"GetLastTradePriceOutput"
gt ltpart name"body" element"xsd1TradePrice"/gt
lt/messagegt
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Relating messages and operations

• Web services are a messaging system
• For a normal method (operation) there will be
  generally two messages
• A message is required to pass the parameters in.
• A message is required to pass the return value
  out
• Even a void return requires an empty return
  message

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Messaging
Parametertype
1. Message in
void myMethod (parametertype)
2. Message out
Empty message
In non-messaging languages this is hidden
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The ltportTypegt

• The types and messages have been defined, but
  they have not been defined in terms of where they
  fit in the functionality of the web service
• This is done within ltportTypegt and ltoperationgt
  elements
• A portType is analogous to a class
• An operation is analogous to a method in that
  class

ltportType name"StockQuotePortType"gt
ltoperation name"GetLastTradePrice"gt ltinput
message"tnsGetLastTradePriceInput"/gt
ltoutput message"tnsGetLastTradePriceOutput"/gt
lt/operationgtlt/portTypegt
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Types of ltoperationgt

• There are four distinct types of operation
• Synchronous
• Request-response - The service receives a message
  and sends a reply
• Solicit-response - The service sends a message
  and receives a reply message
• Asynchronous
• One-way - The service receives a message
• Notification - The service sends a message
• All of these can be defined in WSDL

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Defining the type of operation

• Presence and order of input/output elements
  defines the type of operation.
• Request-response ltinputgtltoutputgt
• Solicit-response ltoutputgtltinputgt
• One-way ltinputgt only
• Notification ltoutputgt only

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The ltbindinggt element

• This element is used to define the mechanism that
  the client will actually use to interact with the
  web service
• There are three possibilities
• SOAP
• HTTP
• MIME
• The most common choice is currently SOAP
• The binding element defines the protocol specific
  information for the portTypes previously defined

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The binding tag

• ltbinding nameez3950SOAPBinding
  typetnsez3950PortTypesgt
• The ltbindinggt tag indicates that we will map a
  ltPort Typegt to a protocol
• ltsoapbinding stylerpc transporthttp//schema
  s.xmlsoap.org/soap/http/gt
• Indicates we will be using the SOAP binding
  extensions to map the operations.
• The alternative to rpc is document.
• ( to use GET/POST use lthttpbindinggt
• to use MIME use ltmimebinding..gt )

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ltbindinggt Example

• Below is an example of a binding element for SOAP

ltbinding name"StockQuoteSoapBinding
type"tnsStockQuotePortType"gt ltsoapbinding
style"document transport"http//schemas.xmlsoap
.org/soap/http"/gt ltoperation
name"GetLastTradePrice"gt ltsoapoperation
soapAction"http//example.com/GetLastTradePrice"/
gt ltinputgt ltsoapbody use"literal"/gt lt/inputgt
ltoutputgt ltsoapbody use"literal"/gt lt/output
gt lt/operationgtlt/bindinggt
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ltservicegt

• The final component of a WSDL file is the
  ltservicegt element
• The ltservicegt element defines ltportgt elements
  that specify where requests should be sent
• The ltsoapaddressgt subelement identifies the URL
  of the service
• The precise content of ltportgt elements will be
  dependent upon the mechanism, i.e. SOAP, HTTP or
  MIME

ltservice name"StockQuoteService"gt ltport
name"StockQuotePort" binding"tnsStockQuoteBindi
ng"gt ltsoapaddress location"http//exampl
e.com/stockquote"/gt lt/portgtlt/servicegt
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Overview of HelloService
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lt?xml version"1.0" encoding"UTF-8"?gt
ltdefinitions name"HelloService"
targetNamespace"http//www.ecerami.com/wsdl/Hello
Service.wsdl" xmlns"http//schemas.xmlsoap.org/ws
dl/" xmlnssoap"http//schemas.xmlsoap.org/wsdl/s
oap/" xmlnstns"http//www.ecerami.com/wsdl/Hello
Service.wsdl" xmlnsxsd"http//www.w3.org/2001/XM
LSchema"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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ltbinding name"Hello_Binding" type"tnsHello_Port
Type"gt ltsoapbinding style"rpc"
transport"http//schemas.xmlsoap.org/soap/http"
/gt ltoperation name"sayHello"gt
ltsoapoperation soapAction"sayHello"/gt
ltinputgt ltsoapbody encodingStyle"htt
p//schemas.xmlsoap.org/soap/encoding/"
namespace"urnexampleshelloservice"
use"encoded"/gt lt/inputgt ltoutputgt
ltsoapbody encodingStyle"http//schemas.xm
lsoap.org/soap/encoding/" namespace"urnexam
pleshelloservice" use"encoded"/gt lt/outputgt
lt/operationgt lt/bindinggt
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ltservice name"Hello_Service"gt
ltdocumentationgtWSDL File for
HelloServicelt/documentationgt ltport
binding"tnsHello_Binding" name"Hello_Port"gt
ltsoapaddress location"http//localhost
8080/soap/servlet/rpcrouter"/ gt lt/portgt
lt/servicegt lt/definitionsgt