Handling Errors Consistently

Error handling in a REST API: making every failure come back to the client in the same, useful shape. An API that returns a stack trace on one endpoint and a bare 500 on another has not been designed; it has accumulated, and clients cannot rely on it. It covers custom exceptions, @ExceptionHandler, @RestControllerAdvice, choosing the status code, how Spring picks between two handlers, and what an error body should contain. It leaves out security errors in depth and error handling in reactive applications.