In the realm of your query, a SOAP service simply functions as a server awaiting POST requests with XML payloads at a designated address.
For instance, if your SOAP web service's address is
http://example.com/service_endpoint
, you can access the service by sending a POST HTTP request to this address containing a SOAP XML message as the payload.
To craft the necessary XML message, it must align with what the service anticipates, an understanding that can be acquired by referring to documentation or utilizing the WSDL of the SOAP web service (learn more about this concept here).
If you are familiar with making POST HTTP requests to a REST service address and delivering an XML payload (even though JSON is commonly used for REST), then you possess the knowledge required to invoke a SOAP web service.
The protocol nature of SOAP streamlines the calling process and outlines the expected XML payload through the WSDL. Various tools interpret the WSDL details and produce a client API that simplifies invocation similar to other methods in your codebase. These tools handle HTTP POST requests and parameter marshalling to XML automatically, possibly causing initial confusion.
Consider this scenario:
If a service features an operation titled savePerson, necessitating firstName and lastName parameters as per the WSDL, your tooling could generate a client method like below:
var response = client.savePerson({ "firstName": "Kim", "lastName": "Seokjin" });
Following execution, you receive a structured response akin to any other object format. Perhaps a promise or event could also surface based on the chosen client implementation. Under the hood, the client triggers an HTTP POST request and transforms the person object into XML, resembling this structure:
POST /service_endpoint
Host: http://example.com
Content-Type: text/xml; charset="utf-8"
Content-Length: nnnn
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
<SOAP-ENV:Body>
<savePerson>
<person>
<firstName>Kim</firstName>
<lastName>Seokjin</lastName>
</person>
</savePerson>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>
If desired, you can manually dispatch this request using your preferred HTTP library instead of relying on a client auto-generated from the WSDL. However, most opt for generated clients to avoid grappling directly with intricate details such as crafting HTTP requests or parsing XML.