How APEX validation works?

As we have mentioned, the APEX built-in Validations mechanism is a server-side mechanism. Just after the Computations of the Page Processing phase completes their run, the validation mechanism kicks in. The APEX engine performs all the validations (subject to their conditions) and accumulates all the validation errors, if any (i.e. validation doesn't stop after the first discovered validation error). If validation errors have occurred, then the APEX engine re-renders the page in a validation error mode. This means that the error message(s) of the failed validation(s) are displayed according to the error message display option(s) that we chose; the page items are populated from Session State, and by default, the Page Rendering Computations and Processes are not fired. APEX 3.0 introduced two specific predefined and declarative conditions that directly relate to the validations result:

• Inline Validation Errors Displayed: This condition allows us to change the default...