WSDL: что это?

WSDL (Web Services Description Language) – is a language used for describing web services. It defines the available functions, operations, and messages that can be performed through web services. WSDL is a standard developed by the World Wide Web Consortium (W3C) and is used to describe how clients can interact with and utilize the functionality of web services.

Using WSDL facilitates integration and interaction between different systems based on web services. WSDL provides a formalized specification for a web service, which includes information about available functions, input and output parameters, data types, and communication protocols that can be used to interact with the web service.

A WSDL file describes the structure of a web service and its methods from the consumer's perspective. It contains information about each available method, including its name, input and output parameters, data types, addresses at which web services are accessible, and more. A WSDL file can be represented in XML format and can be accessed via a URL that determines the location and availability of the web service.

Let's consider an example of XML code that describes a simple web service using WSDL:

<definitions name="MyWebService"
  targetNamespace="http://www.example.com/mywebservice"
  xmlns="http://schemas.xmlsoap.org/wsdl/"
  xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
  xmlns:tns="http://www.example.com/mywebservice"
  xmlns:xsd="http://www.w3.org/2001/XMLSchema">

  <types>
    <xsd:schema targetNamespace="http://www.example.com/mywebservice">
      <xsd:element name="add">
        <xsd:complexType>
          <xsd:sequence>
            <xsd:element name="a" type="xsd:int"/>
            <xsd:element name="b" type="xsd:int"/>
          </xsd:sequence>
        </xsd:complexType>
      </xsd:element>
      <xsd:element name="addResponse">
        <xsd:complexType>
          <xsd:sequence>
            <xsd:element name="result" type="xsd:int"/>
          </xsd:sequence>
        </xsd:complexType>
      </xsd:element>
    </xsd:schema>
  </types>

  <message name="AddRequest">
    <part name="parameters" element="tns:add"/>
  </message>

  <message name="AddResponse">
    <part name="parameters" element="tns:addResponse"/>
  </message>

  <portType name="MyWebServicePortType">
    <operation name="add">
      <input message="tns:AddRequest"/>
      <output message="tns:AddResponse"/>
    </operation>
  </portType>

  <binding name="MyWebServiceBinding" type="tns:MyWebServicePortType">
    <soap:binding style="rpc" transport="http://schemas.xmlsoap.org/soap/http"/>
    <operation name="add">
      <soap:operation soapAction="http://www.example.com/mywebservice/add"/>
      <input>
        <soap:body use="encoded" namespace="http://www.example.com/mywebservice"
          encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"/>
      </input>
      <output>
        <soap:body use="encoded" namespace="http://www.example.com/mywebservice"
          encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"/>
      </output>
    </operation>
  </binding>

  <service name="MyWebServiceService">
    <port name="MyWebServicePort" binding="tns:MyWebServiceBinding">
      <soap:address location="http://www.example.com/mywebservice"/>
    </port>
  </service>

</definitions>

In the example above, we have a simple web service with one method `add`, which takes two integers as input parameters and returns their sum. The WSDL file describes the expected format of input and output data, as well as specifies the communication protocol (in this case, SOAP) and the location of the web service.

Together with the WSDL file, a web service mapping file is usually provided, which describes the actual implementations of web service methods and how they are associated with specific communication protocols (such as HTTP, SOAP, REST, etc.). This allows clients and servers to interact correctly and efficiently.

Using WSDL has many advantages. Firstly, it provides a unified and descriptive way of describing web services, allowing developers of client applications to quickly and easily integrate these services into their applications. Additionally, WSDL enables automatic code generation, making the process of interacting with web services easier and reducing the number of errors and typos.

Thus, WSDL is a powerful tool for describing web services, allowing developers to create, integrate, and use web services in their applications. It defines the interface of the web service and facilitates interaction between the client and the server by providing all the necessary details, such as methods, parameters, and communication protocols.