Hello all :wave::skin-tone-5: Making a post route...

# ktor

[suyash]

Hello all 👋🏾
Making a post route for adding a Task (name,description are only two fields and required too)
1. handling Validation using RequestValidation Plugin
2. handling Exception through StatusPages

post {
    val newTask = getTask()
    val id = helper.createTask(newTask)
    call.respond(HttpStatusCode.Created, mapOf("id" to id))
}

private suspend fun RoutingContext.getTask(): CreateTaskType =
    runCatching { call.receive<CreateTaskType>() }.getOrElse {
        throw BadRequestException("Required fields missing ")
    }
--------------------------------------------------------------------------
validate<CreateTaskType> { task ->
            if (task.name.length > 10)
                ValidationResult.Invalid("XYz")
            else ValidationResult.Valid
        }
--------------------------------------------------------------------------
exception<RequestValidationException> { call, cause ->
            call.respond(HttpStatusCode.BadRequest, cause.reasons.joinToString())
        }
exception<BadRequestException> { call, cause ->
            call.respond(HttpStatusCode.Conflict, cause.message)
        }

My issue is everytime I make a Faulty API Call I get a BadRequestException => 409 with error Message "Required fields missing"
I never get a RequestValidationException => 400 with error Message
how can I prevent that and is there a better way to do such things?

[Bruce Hamilton]

If the request body cannot be deserialised, then it won't make it to the validate function. You can add logging to getTask() to see why the body cannot be deserialized.

[suyash]

when added like this

private suspend fun RoutingContext.getTask(): CreateTaskType =
    runCatching { call.receive<CreateTaskType>() }.getOrElse { e ->
        println(e.message)
        throw BadRequestException("Required fields missing ")
    }

I can see these errors

1. Validation error
Validation failed for CreateTaskType(name=Prepare Monthly Report ....
2. deserialization error
Failed to convert request body to class com.example.data.model.request.CreateTaskType


I am throwing the same error in both cases how can I seperate them
should I use a try catch on call.receive
and then handle RequestValidation exception and CannotTransformContentToTypeException seperately ?

[Bruce Hamilton]

yeah, best to use try-catch and handle the deserialization exceptions when the body is invalid, then allow the validation ones to pass through and get handled by the status pages plugin

you could also include another clause for the deserialization exception in the status pages plugin and remove the exception handling on the receive, assuming you don't have other sources for the same exception that wouldn't create false positives

[suyash]

Got it
For handling serialization errors is there a general exception I can catch ?
for this lib => io.ktor:ktor-serialization-kotlinx-json
the closest I can found is ContentConvertException