WSDL Components

WSDL is an XML file which contains following sections.

• service
• binding
• porttype
• message
• type

Service:

The service element in the WSDL defines the name of the service. Here I used the Employee service. Usually the service name is constructed from the implementation class + “service”. In our case implementation class name is EmployeeServiceImpl. The “service” is appended at the end of the implementation class and the name of our service becomes EmployeeServiceImplService. It also defines the end-point url or web service location which is http://localhost:8080/Employee/employee. The service tag also defines the port name EmployeeServiceImplPort and the binding tns:EmployeeServiceImplPortBinding. 

Binding:

This element defines how the web service accesses the values. The transport=http://schemas.xmlsoap.org/soap/http tells the web service is accessed via http. It also specifies we are using the Document style web service.

Porttype:

Porttype defines the service operations available for the web service. In the Employee service we have two operations.

• addEmployee
• getEmployees

Consider a normal java method which has one optional return type and zero or more input arguments.

Similarly our web service operation also has one input and one output message.

Operation	Messages	Complex Type	Parameter/Return type
addEmployee	tns:addEmployee	addEmployee	{empId,empName,{deptId,deptName}}
	tns:addEmployeeResponse	addEmployeeResponse	Won’t return anything
getEmployees	tns:getEmployees	getEmployees	No Parameters
	tns:getEmployeesResponse	getEmployeesResponse	Employee array

Message:

Is one input and one output message is mandatory? Because normal java method may not return any output and may not accept any input. Similarly it may accept more than one input as argument. So how can we define one input and one output message? 

Types:

Types section has the answer for the questions raised in the messages section. It has attribute schemaLocation which defines the messages in details. Paste this information in a separate url and you will find a page http://localhost:8080/Employee/employee?xsd=1.

Types referring a namespace http://service.sri.com which is reversal of the package structure com.sri.service. Each message was defined in terms of primary attribute. For instance addEmployee method accepts one input argument Employee. Employee has two primary datatype attributes and one user defined Department. All are defined in the complexType section in terms of primary attribute.

getEmployees operation may return zero or more employees. To denote it in the getEmployeeResponse, we have attributes minOccurs=0 and maxOccurs=unbound. 

For the addEmployee operation we need to pass one employee object. What if we pass the NULL to this method? Because of this, addEmployee operation defined minOccurs=0. We may pass employee object or we may not pass anything.

In case of RPC style web service the messages were defined in WSDL itself instead of a separate schema. Only the user defined data types were moved to another schema location.