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 } 

And controller method:

@RequestMapping(value = "/some-info", method = RequestMethod.POST) public Id create(@Valid @RequestBody SomeInfo someInfo) {        ...     } 

@Valid annotation doesn't work.

It seems Spring needs a default parameterless constructor and fancy code above becomes in something ugly (but working) like this:

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

Any good practice to make it less wordy?

Thanks.

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.