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

EGEE is a project funded by the European Union under contract IST-2003-508833

WSDL Web Service Description

Language

www.eu-egee.org

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Objectives

The role of WSDLThe structure of a WSDL document

typesmessageportTypebindingservice

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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 service’s exposed interface

It is what a client sees of your service

WSDL includes information aboutThe data types it usesParameters it requires and returnsGroupings of functionalityThe protocol to be used to access the serviceThe location or address of the service

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WSDL StructureA WSDL document is an XML document

<?xml version="1.0" encoding="UTF-8"?><definitions> <types>

<!– define the types here using XML Schema </types> <message>

<!– XML messages the web service uses are defined here </message> <portType>

<!– define the input and output parameters here - </portType> <binding>

<!– define the network protocol here </binding> <service>

<!– location of the service </service></definitions>

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Referencing between sections

<?xml version="1.0" encoding="UTF-8"?><definitions> <types>

<!– define the data types here using XML Schema </types> <message>

<!– The message will refer to the types defined above </message> <portType>

<!– The operations refer to the messages defined above - </portType> <binding>

<!– A binding refers to a portType defined above </binding> <service>

<!– The service refers to a particular binding defined above </service></definitions>

Each section refers to elements defined in other sections

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Simplified definitions

Each defines things referenced by other sections

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<import> element

<definitionstargetNamespace=“urn:3950”xmlns= “http://schema.xmlsoap.org/wsdl/”xmlns:xsd= “http://www.w3c.org/2001/XMLSchema”xmlns:soap= “http://schemas.xmlsoap.org/wsdl/soap/”xmlnssoapenc= “http://schemas.xmlsoap.org/soap/emcoding/”xmlns:tns= “urn:3950”>

<import namespace= “http://nesc.ac.uk” location= “http://nesc.ac.uk/ez.xsd”/>

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 Namespaceshttp://www.w3.org/2000/10/XMLSchema http://www.w3c.org/2001/XML-Schema-instance

WSDL Namespaceshttp://schemas.xmlsoap.org/wsdl/soap/http://schemas.xmlsoap.org/wsdl/

SOAP Namespaceshttp://schemas.xmlsoap.org/soap/encodinghttp://schemas.xmlsoap.org/soap/envelope

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The <types>

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

<types> <schema targetNamespace="http://example.com/stockquote.xsd" xmlns="http://www.w3.org/2000/10/XMLSchema"> <element name="TradePriceRequest"> <complexType> <all><element name="tickerSymbol" type="string"/></all> </complexType> </element> <element name="TradePrice"> <complexType> <all><element name="price" type="float"/></all> </complexType> </element> </schema> </types>

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The <message>

The <message> element is used to define the messages that will be exchanged between the client and the serviceThese message elements contain <part> elements, which will be using types defined in the types element

All the parts are namespace qualified

<message name="GetLastTradePriceInput"> <part name="body" element="xsd1:TradePriceRequest"/> </message>

<message name="GetLastTradePriceOutput"> <part name="body" element="xsd1:TradePrice"/></message>

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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

void myMethod (parameter:type)

Empty message

Parameter:type

1. Message in

2. Message out

In non-messaging languages this is hidden

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The <portType>

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 <portType> and <operation> elements

A portType is analogous to a classAn operation is analogous to a method in that class

<portType name="StockQuotePortType"> <operation name="GetLastTradePrice"> <input message="tns:GetLastTradePriceInput"/> <output message="tns:GetLastTradePriceOutput"/> </operation></portType>

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Types of <operation>There are four distinct types of operationSynchronous

Request-response - The service receives a message and sends a replySolicit-response - The service sends a message and receives a reply message

AsynchronousOne-way - The service receives a messageNotification - 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 <input><output>

Solicit-response <output><input>

One-way <input> only

Notification <output> only

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The <binding> element

This element is used to define the mechanism that the client will actually use to interact with the web serviceThere are three possibilities1. SOAP2. HTTP3. MIMEThe most common choice is currently SOAPThe binding element defines the protocol specific information for the portTypes previously defined

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The binding tag<binding name=“ez3950SOAPBinding” type=“tns:ez3950PortTypes”>

The <binding> tag indicates that we will map a <Port Type> to a protocol

<soap:binding style=“rpc” transport=“http://schemas.xmlsoap.org/soap/http/”>

Indicates we will be using the SOAP binding extensions to map the operations.

The alternative to “rpc” is “document”.

( to use GET/POST use <http:binding…> to use MIME use <mime:binding…..> )

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<binding> Example

Below is an example of a binding element for SOAP

<binding name="StockQuoteSoapBinding“ type="tns:StockQuotePortType"> <soap:binding style="document“ transport="http://schemas.xmlsoap.org/soap/http"/> <operation name="GetLastTradePrice"> <soap:operation soapAction="http://example.com/GetLastTradePrice"/>

<input> <soap:body use="literal"/></input><output> <soap:body use="literal"/></output>

</operation></binding>

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<service>

The final component of a WSDL file is the <service> elementThe <service> element defines <port> elements that specify where requests should be sent

The <soap:address> subelement identifies the URL of the service

The precise content of <port> elements will be dependent upon the mechanism, i.e. SOAP, HTTP or MIME

<service name="StockQuoteService"> <port name="StockQuotePort" binding="tns:StockQuoteBinding"> <soap:address location="http://example.com/stockquote"/> </port></service>

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Overview of HelloService

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<?xml version="1.0" encoding="UTF-8"?> <definitions name="HelloService" targetNamespace="http://www.ecerami.com/wsdl/HelloService.wsdl" xmlns="http://schemas.xmlsoap.org/wsdl/" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:tns="http://www.ecerami.com/wsdl/HelloService.wsdl" xmlns:xsd="http://www.w3.org/2001/XMLSchema">  

<message name="SayHelloRequest"> <part name="firstName" type="xsd:string"/>

</message> <message name="SayHelloResponse">

<part name="greeting" type="xsd:string"/> </message>   <portType name="Hello_PortType">

<operation name="sayHello"> <input message="tns:SayHelloRequest"/> <output message="tns:SayHelloResponse"/>

</operation> </portType>  

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<binding name="Hello_Binding" type="tns:Hello_PortType"> <soap:binding style="rpc"

transport="http://schemas.xmlsoap.org/soap/http"/> <operation name="sayHello">

<soap:operation soapAction="sayHello"/> <input>

<soap:body encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"

namespace="urn:examples:helloservice" use="encoded"/> </input> <output>

<soap:body encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"

namespace="urn:examples:helloservice" use="encoded"/> </output>

</operation> </binding>

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<service name="Hello_Service"> <documentation>WSDL File for

HelloService</documentation> <port binding="tns:Hello_Binding" name="Hello_Port"> <soap:address

location="http://localhost:8080/soap/servlet/rpcrouter"/></port>

</service> </definitions>