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What is WSDL , Use of WSDL in java Web Services



WSDL (Web Services Description Language) is an XML file that describes a web service and all its operations,input and output messages as a collection of access endpoints. WSDL defines a web service in an abstract way with separate definitions and terminology.By using WSDL, Our application can able to connect and use a web service.

 

 

The main elements in the WSDL file as follows :

WSDL in java Web Services

WSDL in java Web ServicesThe  * mark represents , that element my appear one or more than one.

 

WSDL in java Web Services<definitions> : It is the root element for the WSDL document.It acts as a container for the service with global namespaces declarations.
Namespace :XML namespaces are a mechanism that ensures that there are no name conflicts (or ambiguity) when combining XML documents or referencing an XML element.
Ex: xmlns:soap=”http://schemas.xmlsoap.org/wsdl/soap/”
xmlns : Reserved word to declare a namespace
soap : Is the prefix with the namespace “http://schemas.xmlsoap.org/wsdl/soap/”
http://schemas.xmlsoap.org/wsdl/soap/ : XML location

 

WSDL in java Web Services<import> :This element imports the namespace of another file, similar to the java import statement.It includes all elements for the given namespace are included at the location of the <import> element in the used document.

 

 <types> : This element acts as a container for defining the data types.It provides information about any complex data types used in the WSDL document. When simple types are used the document does not need to have a types section. It has a sub element <schema>.

 

  <message>: It is An abstract definition of the data being communicated ,  it reference the types defined in the <types> section (schemaLocation).The <message> element is uniquely identified by it’s name attribute.It has a sub element <part>.

 

 <portType> : It is An abstract set of operations supported by one or more endpoints. It has a sub element <operation> is an abstract definition of an action (like java method definition) supported by a web service.

<operation> has two sub elements <input> and <output>.

<input>  defines the input message. <output> defines the  output message. Both <input> and <output> elements reference <message> elements defined in the same WSDL document or an imported one.

 

 <binding> : Describes how the operation is invoked by specifying concrete protocol and data format specifications for the operations and messages.The name attribute defines a unique identifier for this binding.

The value of the  type attribute must be the name of one of the <portType> elements contained within the same WSDL document or in an imported one.

 

 <service> : This element is useful to identify the service.By using the service name , we can get the port to use all operations that are available in the web services.

<service> has two sub elements <documentation> and <port>.

<documentation> is an optional element that describes the web service.

Another element <port>,it has one sub element <soap:address> which identifies the URL  (location) of the web service.




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