What is WSDL in Web Services

WSDL Enters….

A WSDL document is just a simple XML document.

It contains set of definitions to describe a web service.

WSDL document fulfills all the above requirements

• Requirement 1 – Where is the service hosted    
• Requirement 2 – What protocol to use to talk to the service             
• Requirement 3 – What are the operations             
• Requirement 4 – What are the parameters             
• Requirement 5 – What is the datatype of the messages

Introducing WSDL

• WSDL stands for Web Services Description Language
• WSDL is written in XML
• WSDL is used to describe Web services
• WSDL is also used to locate Web services
• WSDL is a W3C recommendation

WSDL Document Structure

WSDL Ports

• The 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 element can be compared to a function library (or a module, or a class) in a traditional programming language

Operation Types

Type                                     Definition
One-way                              The operation can receive a message but will not return a response
Request-response               The operation can receive a request and will return a response
Solicit-response                   The operation can send a request and will wait for a response
Notification                           The operation can send a message but will not wait for a response

One-way operation type        

 The operation can receive a message but will not return a response

Request-response operation type

The operation can receive a request and will return a response

Now, a web service operation can take only one parameter.  But I want to pass multiple parameters……what do I need to do

WSDL Messages

• The 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.

I want to pass a complex object to my web service……what do I need to do

WSDL Types

• The element defines the data type that are used by the web service.
• For maximum platform neutrality, WSDL uses XML Schema syntax to define data types.

I want my web service to be accessible to a HTTP client, as well as to a RMI client and a SOAP client……what do I need to do

WSDL Bindings

The element defines the message format and protocol details for each port.

Binding

• name – can be anything
• Type – points to port

Soap:binding

• Style – rpc or document
• Transport – soap protocol to use

Operation

• Defines each operation the the service exposes

WSDL Bindings

• The element provides specific details on how a portType operation will actually be transmitted over the wire.
• The bindings can be made available via multiple transports, including HTTP GET, HTTP POST, or SOAP.
• The bindings provide concrete information on what protocol is being used to transfer portType operations.
• For SOAP protocol, the binding is , and the transport is SOAP messages on top of HTTP protocol.
• WSDL 1.1 includes built-in extensions for SOAP 1.1. This enables you to specify SOAPspecific details, including SOAP headers, SOAP encoding styles, and the SOAPAction HTTP header. The SOAP extension elements include:
• soap:binding
• soap:operation
• soap:body
• You can specify multiple bindings for a single portType.

WSDL Services

The element connects the binding to an actual URL where the service is available.

A service element describes a Web service as a collection of port elements. A port element defines a specific network address for a binding. The sample below shows the basic outline of a service that supplies an address for a SOAP binding:

The ServiceName sets the name of the service. The PortName sets the name of the specific address. The BindingRef refers to the name of a binding element. The BindingRef must be namespace qualified if the targetNamespace for the WSDL definitions element is not the same as the default namespace.

Example