Understanding SOAP API: Real-World Uses and How to Create & Integrate It

When discussing web services, REST is often the main focus. But in industries where security, reliability, and strict standards are critical, SOAP (Simple Object Access Protocol) still plays a vital role.

Let’s break down what SOAP APIs are, where they’re used in the real world, and how you can create and integrate one.

What is a SOAP API?
SOAP is a protocol designed to exchange structured data through XML messages over a network. Unlike REST, which is more flexible, SOAP enforces strict standards that make it suitable for complex operations in enterprise environments.

Key features include:

• Platform-agnostic XML-based communication
• Strong error handling
• Built-in security via WS-Security
• Contract-based communication using WSDL (Web Services Description Language)

Where is SOAP Used in the Real World?

SOAP is widely used in:

• Banking & Finance (e.g., payment gateways, transaction systems)
• Telecommunication (e.g., service provisioning)
• Healthcare (e.g., HL7 data exchange)
• Insurance (e.g., policy and claim systems)
• Government systems (e.g., e-filing, identity verification)

These industries often require strict validation, message integrity, and robust security, all of which SOAP provides.

How to Create a SOAP API?

You can build a SOAP web service using different programming languages.. Here’s a simple outline using Java (JAX-WS):

1. Define the Service Interface
@WebService
public interface CalculatorService {
@WebMethod
int add(int a, int b);
}

2. Implement the Interface
@WebService(endpointInterface = "com.example.CalculatorService")
public class CalculatorServiceImpl implements CalculatorService {
public int add(int a, int b) {
return a + b;
}
}

3. Publish the Service
public class App {
public static void main(String[] args) {
Endpoint.publish("http://localhost:8080/calculator", new CalculatorServiceImpl());
}
}

This will expose a WSDL at http://localhost:8080/calculator?wsdl

How to Integrate a SOAP API?

You can consume a SOAP service in many ways, depending on the platform:
In Java (JAX-WS):

1. Use wsimport to generate client classes from the WSDL.
In .NET:
2. Add a service reference by specifying the WSDL URL.
In PHP:
$client = new SoapClient("http://example.com/service?wsdl");
$response = $client->SomeMethod(['param1' => 'value']);

Using Postman (for testing):

1. Set the method to POST
2. Add Content-Type: text/xml and SOAPAction headers
3. Paste the XML request in the body and hit send