Understanding SOAP API with WSDL Examples

What is SOAP API?

SOAP (Simple Object Access Protocol) is a protocol used for exchanging structured information in the implementation of web services. It relies on XML to encode its HTTP-based messages.

What is WSDL?

WSDL (Web Services Description Language) is an XML-based language used to describe the services offered by a SOAP API. It provides details on how to interact with the service, including the available methods and data types.

Example SOAP API Using WSDL

To illustrate the usage of a SOAP API with WSDL, let’s consider an example of a simple weather service. Below is a sample WSDL definition for a fictional weather API:

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

  <types>
    <xsd:schema targetNamespace="http://example.com/weather">
      <xsd:element name="GetWeatherRequest">
        <xsd:complexType>
          <xsd:sequence>
            <xsd:element name="CityName" type="xsd:string"/>
          </xsd:sequence>
        </xsd:complexType>
      </xsd:element>
      <xsd:element name="GetWeatherResponse">
        <xsd:complexType>
          <xsd:sequence>
            <xsd:element name="Temperature" type="xsd:float"/>
            <xsd:element name="Condition" type="xsd:string"/>
          </xsd:sequence>
        </xsd:complexType>
      </xsd:element>
    </xsd:schema>
  </types>

  <message name="GetWeatherRequestMessage">
    <part name="parameters" element="tns:GetWeatherRequest"/>
  </message>

  <message name="GetWeatherResponseMessage">
    <part name="parameters" element="tns:GetWeatherResponse"/>
  </message>

  <portType name="WeatherServicePortType">
    <operation name="GetWeather">
      <input message="tns:GetWeatherRequestMessage"/>
      <output message="tns:GetWeatherResponseMessage"/>
    </operation>
  </portType>

  <binding name="WeatherServiceBinding" type="tns:WeatherServicePortType">
    <soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http"/>
    <operation name="GetWeather">
      <soap:operation soapAction="http://example.com/weather/GetWeather"/>
      <input>
        <soap:body use="literal"/>
      </input>
      <output>
        <soap:body use="literal"/>
      </output>
    </operation>
  </binding>

  <service name="WeatherService">
    <port name="WeatherServicePort" binding="tns:WeatherServiceBinding">
      <soap:address location="http://api.example.com/weather"/>
    </port>
  </service>
</definitions>

How to Use the Weather SOAP API

Step 1: Create the SOAP Request

To get the weather for a specific city, you would create a SOAP request like this:

<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" 
               xmlns:tns="http://example.com/weather">
  <soap:Header/>
  <soap:Body>
    <tns:GetWeatherRequest>
      <tns:CityName>New York</tns:CityName>
    </tns:GetWeatherRequest>
  </soap:Body>
</soap:Envelope>

Step 2: Sending the Request

You can use various programming languages to send this SOAP request. Below is an example using Python with the requests library:

```python
import requests

url = ‘http://api.example.com/weather’
headers = {’Content-Type’: ‘text/xml; charset=utf-8’}

soap_request = ‘’’