SOAP Web Services Overview
By the end of this lesson, you'll be able to:
- Explain what SOAP is and how it differs from a REST/JSON callout
- Recognize a WSDL and its role in generating Apex classes
- Understand when SOAP still appears in real integration work
Prerequisites: "REST Resources in Apex (@RestResource)"
SOAP vs REST, at a glance
| REST (this module\'s other lessons) | SOAP | |
|---|---|---|
| Data format | Usually JSON | Always XML (Lesson 3\'s DOM classes) |
| Contract | Informal (API documentation) | Formal — a WSDL file defines every operation precisely |
| Flexibility | Lightweight, flexible | Rigid, but strongly typed and validated |
SOAP predates REST's current dominance and remains common specifically in older enterprise systems — banking, insurance, and government integrations especially.
What a WSDL does
A WSDL (Web Services Description Language) file is a formal, machine-readable contract describing every operation a SOAP service offers, its parameters, and its expected responses. Salesforce can generate a complete set of Apex classes directly from a WSDL file (via Setup) — turning a SOAP service's contract into ready-to-use Apex classes automatically, rather than hand-writing the XML request/response parsing yourself.
Using a generated SOAP class
// After generating classes from a WSDL, calling a SOAP service
// looks almost like calling a regular Apex method:
ExternalBankingService.BankingPort service = new ExternalBankingService.BankingPort();
ExternalBankingService.AccountBalanceResponse response = service.getAccountBalance('ACC-123');This is the real value of WSDL-generated classes: once generated, calling a SOAP service reads almost like a normal method call (Module 9) — the generated classes handle the underlying XML request/response construction entirely behind the scenes.
Exercise
As a comment, explain what a WSDL file is and what generating Apex classes from it actually saves you from doing manually.
Show hint
Think about what Lesson 3's DOM.Document parsing would otherwise require.
SOAP Web Services Overview Quiz
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Summary
SOAP is an older, more rigid web service standard, XML-based and defined by a formal contract (a WSDL) — genuinely less common in new integrations, but still worth recognizing.