About Web Services Definition Language (WSDL)

Web Services Definition Language (WSDL):

• WSDL-Service Description:

Service Description carries information about the service such as the input or output parameter, the location of the service, port type, binding information, and so on.

• Web Services Definition Language

– http://www.w3.org/TR/wsdl/

• An XML-based language for describing Web Services

– what the service does (description)

– how to use it (method signatures)

– where to find the service

• It does not depend on the underlying protocol

• WSDL is an XML grammar for describing a web service as a collection of access endpoints.

• Capable of exchanging messages in a procedure or document-oriented fashion.

• A WSDL document is a recipe used to automate the details involved in application-to-application communication.

Anatomy of a WSDL Document

The following code shows the major elements that may appear in a WSDL document.

An asterisk (*) next to an element indicates that more than one of these elements may appear.

< definitions>

<import>*<types><schema></schema>*</types>

<message>*<part></part>*</message>

<PortType>*

<operation>*<input></input><output></output><fault></fault>*

</operation>

</PortType>

<binding>*<operation>*<input></input><output></output>

</operation>

</binding>

<service>*<port></port>*</service>

< /definitions >

WSDL Elements

• Types – will give namespace and schema location.

• Message - Request/response messages.

• Operation - Name of operation.

• Port Type – Actual WebService.

• Binding – Binds on particular port.

• Port - URL of WS on which it is running.

• Service – web Service.

<definitions> Element

The <definitions> element in a WSDL document acts as a

container for the service description.

It provides a place to do global declarations of namespaces

that are intended to be visible throughout the rest of the

document.

< definitions targetNamespace="urn:3950" xmlns="http://schemas.xmlsoap.org/wsdl/"

xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/ “ xmlns:tns="urn:3950">

<import> Element

The <import> element serves a purpose similar to the #include directive in the C/C++ programming language.After the <definitions> element, we see an <import> element:

< definitions targetNamespace="urn:3950" xmlns="http://schemas.xmlsoap.org/wsdl/"

xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"

xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/“ xmlns:tns="urn:3950">

< import namespace="http://asf.gils.net/xer" location="http://asf.gils.net/xer/ez.xsd"/>

<types> Element

• The <types> element in a WSDL document acts as a container for defining the data types used in <message> elements.

• <message> elements define the format of messages interchanged between a client and a web service.

• The <types> element has zero or more <schema> sub elements.

<message> Element

• The <message> element is used to model the data exchanged as part of a web service.

• <message> elements reference the types defined in the <types> section.

• A message consists of one or more <part> subelements.

• A <part> subelement identifies the individual pieces of data that are part of this data message and the datatypes that the pieces adhere to.

<portType> Element

• The <portType> element specifies a subset of operations supported for an endpoint of a web service.

• In a sense, a <portType> element provides a unique identifier to a group of actions that can be executed at a single endpoint

<binding> Element

A <binding> element is a concrete protocol and data format specification for a <portType>element.

It is where you would use one of the standard binding extensions-HTTP, SOAP, or MIME-or create one of your own.

<service> Element

The <service> element typically appears at the end of a WSDL document and identifies a web service.

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

< wsdl:definitions targetNamespace="http://emp" mlns:apachesoap="http://xml.apache.org/xml-soap" xmlns:impl="http://emp" xmlns:intf="http://emp" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/" xmlns:wsdlsoap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:xsd="http://www.w3.org/2001/XMLSchema">

< !--WSDL created by Apache Axis version: 1.4 Built on Apr 22, 2006 (06:55:48 PDT)-->

<wsdl:types>

<schema elementFormDefault="qualified" targetNamespace="http://emp" xmlns="http://www.w3.org/2001/XMLSchema">

<element name="getName">

<complexType>

<sequence>

<element name="sName" type="xsd:string"/>

</sequence>

</complexType>

</element>

<element name="getNameResponse">

<complexType>

<sequence>

<element name="getNameReturn" type="xsd:string"/>

</sequence>

</complexType>

</element> </schema> </wsdl:types>

<wsdl:message name="getNameResponse">

<wsdl:part element="impl:getNameResponse" name="parameters"/>

</wsdl:message>

<wsdl:message name="getNameRequest">

<wsdl:part element="impl:getName" name="parameters"/>

</wsdl:message>

<wsdl:portType name="employee">

<wsdl:operation name="getName">

<wsdl:input message="impl:getNameRequest" name="getNameRequest"/>

<wsdl:output message="impl:getNameResponse" name="getNameResponse"/>

</wsdl:operation>

</wsdl:portType>

<wsdl:binding name="employeeSoapBinding" type="impl:employee">

<wsdlsoap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http"/>

<wsdl:operation name="getName">

<wsdlsoap:operation soapAction=""/>

<wsdl:input name="getNameRequest">

<wsdlsoap:body use="literal"/>

</wsdl:input>

<wsdl:output name="getNameResponse">

<wsdlsoap:body use="literal"/>

</wsdl:output>

</wsdl:operation>

</wsdl:binding>

<wsdl:service name="employeeService">

<wsdl:port binding="impl:employeeSoapBinding" name="employee">

<wsdlsoap:address location="http://localhost:8080/employee/services/employee"/>

</wsdl:port>

</wsdl:service>

</wsdl:definitions>

Web Service Request/ Response