kotlin and @Valid Spring annotation

Question

I have an entity:

class SomeInfo(
        @NotNull @Pattern(regexp = Constraints.EMAIL_REGEX) var value: String) {
    var id: Long? = null
}

Answer 1

Seems Spring needs these annotations to be applied to a field. But Kotlin will apply these annotations to the constructor parameter. Use field: specifier when applying an annotation to make it apply to a field. The following code should work fine for you.

class SomeInfo(
    @field:NotNull
    @field:Pattern(regexp = Constraints.EMAIL_REGEX)
    var value: String
) {
    var id: Long? = null
}

Answer 2

As an alternative to Michal's answer, annotating the getter also works.

class SomeInfo(
    @get:NotNull
    @get:Pattern(regexp = Constraints.EMAIL_REGEX)
    var value: String
) {
    var id: Long? = null
}

The annoying part is, that not using @get: or @field: will annotate the constructor parameter. This is still valid kotlin code (so you don't get an error). It's just useless in these use cases.

Answer 3

Also your rest controller should be marked by @Validated annotation

Answer 4

If you use IntelliJ to convert Java to Kotlin, the @Valid annotation in the Spring Controller method may eventually be attached to the type, instead of the variable. This would break the validation.

For example, the convertion could result in

@PostMapping
public Id create(@RequestBody someInfo: @Valid SomeInfo) {
    ...
}

This is not validating. The @Valid has to be moved to a variable like this:

@PostMapping
public Id create(@RequestBody @Valid someInfo: SomeInfo) {
    ...
}