Following is the WSDL file that is provided to demonstrate a simple WSDL program.
Assuming the service provides a single publicly available function, called sayHelloWorld. This function expects a single string parameter and returns a single string greeting. For example if you pass the parameter world then service function sayHelloWorld returns the greeting, "Hello, world!! Dinesh on Java".
Web Service Name : HelloWorldService
This WSDL example contains:
- SOAP Protocol
- Document Literal Binding
- No optional SOAP Header included in WSDL
- SOAP Body
Content of HelloWorldService.wsdl file
<definitions name="HelloWorldService"
targetNamespace="http://www.dineshonjava.com/wsdl/HelloWorldService.wsdl"
xmlns="http://schemas.xmlsoap.org/wsdl/"
xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns:tns="http://www.dineshonjava.com/wsdl/HelloWorldService.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="HelloWorld_PortType">
<operation name="sayHelloWorld">
<input message="tns:SayHelloRequest"/>
<output message="tns:SayHelloResponse"/>
</operation>
</portType>
<binding name="HelloWorld_Binding" type="tns:HelloWorld_PortType">
<soap:binding style="rpc"
transport="http://schemas.xmlsoap.org/soap/http"/>
<operation name="sayHelloWorld">
<soap:operation soapAction="sayHelloWorld"/>
<input>
<soap:body
encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"
namespace="urn:examples:helloworldservice"
use="encoded"/>
</input>
<output>
<soap:body
encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"
namespace="urn:dineshonjava:helloworldservice"
use="encoded"/>
</output>
</operation>
</binding>
<service name="HelloWorld_Service">
<documentation>WSDL File for HelloWorldService</documentation>
<port binding="tns:HelloWorld_Binding" name="HelloWorld_Port">
<soap:address
location="http://www.dineshonjava.com/SayHelloWorld/">
</port>
</service>
</definitions>

Analysis of the Example
1. Definition : HelloWorldService
2. Type : Using built-in data types and they are defined in XMLSchema.
3. Message :
- sayHelloRequest : firstName parameter
- sayHelloresponse: greeting return value
4. Port Type: sayHelloWorld operation that consists of a request and response service.
5. Binding: Direction to use the SOAP HTTP transport protocol.
6. Service: Service available at http://www.dineshonjava.com/SayHelloWorld/.
7. Port: Associates the binding with the URI http://www.dineshonjava.com/SayHelloWorld/ where the running service can be accessed.
WSDL Ports
The <portType> element is the most important WSDL element.
It describes a web service, the operations that can be performed, and the messages that are involved.
The <portType> element can be compared to a function library (or a module, or a class) in a traditional programming language.
WSDL Messages
The <message> element defines the data elements of an operation.
Each message can consist of one or more parts. The parts can be compared to the parameters of a function call in a traditional programming language.
WSDL Types
The <types> element defines the data types that are used by the web service.
For maximum platform neutrality, WSDL uses XML Schema syntax to define data types.
WSDL Bindings
The <binding> element defines the data format and protocol for each port type.
References
Wikipedia for WSDL