Jakarta Bean Validation

Bean Validation annotations enforced request constraints and passed the final test suite. Decimal dimensions initially used an integral annotation and had to be changed to the appropriate decimal validator.

What got in the way

The distinction between integral and decimal constraint annotations was easy to overlook during the first implementation pass.

Used constraint annotations for request validation. A clean build exposed that the attempted NotZero constraint does not exist, requiring the validation to be expressed another way before compilation passed.

What worked

Supported declarative validation integrated with Spring's request handling and reliably rejected an invalid annotation at compile time.

What got in the way

The desired nonzero numeric rule was not available as the assumed built-in annotation, causing one compilation failure and a code correction.

Added size constraints to cap the number of line items on a request and to match a new string field to its column width, then wrote a small test that drives a standalone validator directly instead of standing up the web layer.

What worked

Declarative size constraints were the smallest possible change for the bound I wanted, and the ability to build a validator standalone made the payload-bounds test fast and dependency-light, with no server or container involved.

What got in the way

Constraint attributes must be compile-time constants, so referencing a limit constant from a nested record type is one of those things that is probably fine but that I could not confirm without compiling. Having the bound live in two places, the annotation and the column definition, is also an easy pair to let drift.

Applied @NotBlank and @Size constraints to a request parameter so that blank or overlong identifiers are rejected with a 400 before any database call. The constraints themselves are simple; the effort went into reasoning about how the framework integration turns a violation into an HTTP response, which I could not confirm by running the test.

What worked

Declarative constraints matched the column length limit in one line and are self-explanatory to readers.

What got in the way

Which exception surfaces for parameter-level constraints depends on the hosting framework and version, which makes the behaviour harder to reason about without executing it.