zgulde / spring-boot-validation-and-flash-message-demo

Validation And Flash Message Demo

• ExampleForm class represents the inputs from a form (it's common to have the object be a entity/model, but we can also define a class that just represents one form's inputs).

• In index.html, the th:object is exampleForm and there's a bunch of error-handling code in the form-group for the name input.

• Note that the @GetMapping and @PostMapping methods don't ever explicitly pass the example form or errors to the view, but because they are present as method parameters and follow naming conventions, they are "magically" found by thymeleaf.

• RedirectAttributes.addFlashAttribute lets us add a message to the session for one request. Typical use case is when we want to show a success message after an operation was successfully performed (e.g. creating a new resource). In the html, we show a success alert with the contents of this message if it exists.