Error handling is the unsung hero of clean API design. While a flawless API is an illusion, how you manage its imperfections can make or break the developer experience. Whether you’re crafting API endpoints or writing tests for them, understanding the order of operations for error handling is crucial.

Error Handling in API Endpoints

Error handling in API endpoints is like constructing a safety net. You want to catch issues early, guide users clearly, and ensure the system’s integrity. Here’s a logical progression to follow:

1. Validate Inputs
  • Start at the door: Check your inputs before they enter your application.
(defn validate-user-input [data]
  (if (and (:username data) (:email data))
    data
    (throw (ex-info "Invalid input" {:status 400 :error "Missing fields"}))))
2. Handle Authentication and Authorization
  • After validation, ensure the user is who they claim to be.
  • Reject requests lacking proper credentials or permission early to avoid unnecessary processing.
  • 3. Guard Against Runtime Failures
  • Surround database calls, API integrations, or complex operations with error-handling wrappers.
4. Provide Meaningful Responses
  • Every error message should:
  • Include an HTTP status code (400, 403, 404, 500, etc.).
  • Clearly describe the issue (without revealing sensitive details).
{
  "status": 400,
  "error": "Missing required field: username"
}
5. Catch Unhandled Exceptions
  • Use a global error handler to catch unanticipated issues and ensure graceful API responses.
  • In Clojure, middleware like ring.middleware.error can help.