when validating a controller using kotlin/spring, how would you validate that a date is after the ot...

# spring

[xii]

when validating a controller using kotlin/spring, how would you validate that a date is after the other? I tried creating a data class and having an

@AssertTrue

in the data class, but I'm getting an unused function error (🧵 )

[xii]

example:

@GetMapping("/test")
fun validTest(@PathVariable params: Params){
  foo(params.from, <http://params.to|params.to>)
}

data class Params(val from: Instant, val to: Instant){
  @AssertTrue("from should be before to")
  fun areDatesValid(): Boolean {
    return from.isBefore(to)
  }
}

[xii]

(id rather not create a new annotation for this)

[Jacob]

Why are you getting an unused function error on a public function? Does the error go away if you use it in a unit test?

[xii]

yes

[Tom Hermann]

You were super close. The issue is that your @AssertTrue annotation was not on a function that conforms to the JavaBean spec (boolean accessors are expects to start with is or get )

I’d also mark your parameter object as @Valid, so validation is applied. You probably already have it, but you also need this dependency to get all the validation goodness:

implementation("org.springframework.boot:spring-boot-starter-validation")

Untitled.cpp

[Jacob]

The issue is that your @AssertTrue annotation was not on a function that conforms to the JavaBean spec

This doesn't sound right. See https://docs.jboss.org/hibernate/stable/validator/reference/en-US/html_single/#chapter-method-constraints

[Tom Hermann]

@Jacob I agree that this is a bit confusing, per that documentation I’d expect to be able to validate any arbitrarily named method.

I don’t have time to dig into the root cause of this behavior, but I did create a project that demonstrates the name change exhibiting the behavior the OP desired. Here is the test that shows that naming was the culprit in this case:

https://github.com/tomhermann/spring-validation-example/blob/main/src/test/kotlin/com/zombietank/validation/MethodConstraintControllerTest.kt