What is WSDL in Web Services
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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
- 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
- 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
|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
- 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.
I want to pass a complex object to my web service……what do I need to do
- The <types> 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
The <binding> element defines the message format and protocol details for each port.
- name – can be anything
- Type – points to port
- Style – rpc or document
- Transport – soap protocol to use
- Defines each operation the the service exposes
- The <binding> 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 <soap:binding>, 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:
- You can specify multiple bindings for a single portType.
The <services> 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:
<port name=”PortName” binding=”BindingRef“>
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.
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