WSDL (Web Services Description Language)

WSDL (Web Services Description Language) is an XML-based language for describing Web services and how to access them.

WSDL is used to describe Web services

WSDL is also used to specifies the location of the service and the operations (or methods) the service exposes.

WSDL is written in XML

WSDL is an XML document

The WSDL Document Structure:-

It contains set of definitions to describe a web service.A WSDL document describes a web service using these major elements:

<types>	The data types used by the web service
<message>	The messages used by the web service
<portType>	The operations performed by the web service
<binding>	The communication protocols used by the web service

A WSDL document can also contain other elements, like extension elements, and a service element that makes it possible to group together the definitions of several web services in one single WSDL document.

WSDL Ports:-The <portType> element can be compared to a function library (or a module, or a class) in a traditional programming language.
ex:-
<portType name="EmployeeDetail">
  <operation name="getEmployeeDetail">
    <input message="getEmployeeIDRequest"/>
    <output message="getEmployeeDetailResponse"/>
  </operation>
</portType>

WSDL Messages:-The <message> element defines the data elements of an operation.
ex:-
<message name="getEmployeeIDRequest">
  <part name="ID" type="xs:integer"/>
</message>

<message name="getEmployeeDetailResponse">
  <part name="value" type="xs:string"/>
</message>

WSDL Types:-The <types> element defines the data types that are used by the web service.

WSDL Bindings:-The <binding> element defines the message format and protocol details for each port.
The binding element has two attributes - name and type.The name attribute (you can use any name you want) defines the name of the binding, and the type attribute points to the port for the binding.
<binding type="glossaryTerms" name="b1">
   <soap:binding style="document"
   transport="http://schemas.xmlsoap.org/soap/http" />
   <operation>
     <soap:operation soapAction="http://example.com/getTerm"/>
     <input><soap:body use="literal"/></input>
     <output><soap:body use="literal"/></output>
  </operation>
</binding>
The operation element defines each operation that the port exposes.