Kalidation = A Kotlin validation DSL
Objective
Creation of a validation DSL which allows this kind of fluent code:
val spec = validationSpec {
constraints<Foo> {
property(Foo::bar) {
notBlank()
inValues("GREEN", "WHITE", "RED")
}
property(Foo::bax) {
min(3)
email()
}
property(Foo::baz) {
validByScript(lang = "groovy", script = "baz.validate()", alias = "baz")
}
returnOf(Foo::validate) {
assertTrue()
}
returnOf(Foo::total) {
min(10)
}
}
}This DSL does Type Checking on the properties of the bean to validate, ie constraints on Foo should only contain
properties of Foo.
It also does Type Checking on the rule: eg: an email() constraint is not applicable to an numeric property, so you
shouldn’t be allowed to put a constraint to such a property.
Furthermore, this DSL decouples your domain classes from any validation framework and annotations and, as such, respect the Clean Architecture.
Usage
val spec = validationSpec(messageBundle = "MyMessages", locale = Locale.FRENCH) {
constraints<MyClass> {
property(MyClass::color) {
notBlank()
inValues("GREEN", "WHITE", "RED")
size(3, 5)
}
property(MyClass::token) {
regexp("[A-Za-z0-9]+")
}
property(MyClass::date) {
future()
}
returnOf(Foo::validate) {
assertTrue()
}
property(MyClass::innerClass) {
valid()
}
}
constraints<InnerClass> {
property(InnerClass::amount) {
negativeOrZero()
}
property(InnerClass::emailList) {
notEmpty()
eachElement {
notNull()
email()
}
}
}
}
val myClass = MyClass("BLUE", "foobar", LocalDateTime.parse("2017-12-03T10:15:30"), ...)
val validated = spec.validate(myClass) In this example, validated is an Arrow Validated object, which we can transform through Arrow
built-in functions: when, fold, getOrElse, map, etc.
See Arrow Validated for more documentation.
Example with fold:
val validated = spec.validate(myClass)
validated.fold(
{ throw ValidationException(it) },
{ return it }
)Example with when:
val validated = spec.validate(myClass)
when (validated) {
is Valid -> return validated.a
is Invalid -> throw ValidationException(validated.e)
}Structure of the validation result:
The validation result structure is a Set of ValidationResult instances.
data class ValidationResult(
val fieldName: String,
val invalidValue: Any?,
val messageTemplate: String,
val message: String
)The ValidationResult object contains the name and the value of the field in error, the message template and the i18n
corresponding message.
Implemented validation functions on properties
All classes
- notNull()
- isNull()
- valid(), used for cascading validation (on an inner class)
- validByScript(lang: String, script: String, alias: String = "_this", reportOn: String = "") - supports javascript, jexl and groovy scripts which returns a Boolean
Array
- size(val min 80D0 : Int, val max: Int)
- notEmpty()
Collections (List, Set, etc.)
- size(val min: Int, val max: Int)
- notEmpty()
- subSetOf(val completeValues: List)
Maps
- size(val min: Int, val max: Int)
- notEmpty()
- hasKeys(val keys: List)
Boolean
- assertTrue()
- assertFalse()
CharSequence (String, StringBuilder, StringBuffer, etc.)
- notBlank()
- notEmpty()
- size(val min: Int, val max: Int)
- regexp(val regexp: String)
- email()
- phoneNumber(val regionCode: String)
- inValues(val values: List)
- negativeOrZero()
- positiveOrZero()
- negative()
- positive()
- range(val min: Long, val max: Long)
- min(val value: Long)
- max(val value: Long)
- decimalMin(val value: String, val inclusive: Boolean)
- decimalMax(val value: String, val inclusive: Boolean)
- digits (val integer: Int, val fraction: Int)
- iso8601Date()
- inIso8601DateRange(startDate: String, stopDate: String)
Number (Integer, Float, Long, BigDecimal, BigInteger, etc.)
- range(val min: Long, val max: Long)
- negativeOrZero()
- positiveOrZero()
- negative()
- positive()
- min(val value: Long)
- max(val value: Long)
- decimalMin(val value: String, val inclusive: Boolean)
- decimalMax(val value: String, val inclusive: Boolean)
- digits (val integer: Int, val fraction: Int)
Temporal (LocalDate, LocalDateTime, ZonedDateTime, etc.)
- future()
- past()
- futureOrPresent()
- pastOrPresent()
For all methods, an optional message: String? parameter can be used to override the resource bundle message.
Validation on method return type
It is also possible to specify a validation on a return type of a method:
returnOf(Foo::validate) {
notNull()
assertTrue()
//etc...
}The method returOf accepts an optional alias parameter to report the violation on a specific property rather than
the method.
In this example, if the method validate returns false, the ValidationResult object will look like:
Invalid(e=[ValidationResult(
fieldName=validate.<return value>,
invalidValue=false,
messageTemplate={javax.validation.constraints.AssertTrue.message},
message=doit être vrai)]
)
Validation of containers (List, Maps, Sets, etc)
It is possible to validate each property inside a container:
eachElement(Foo::emails) {
notNull()
email()
//etc...
}In case of more complex containers (ex: Map of List), a NonEmptyList of indexes enables a navigation inside the
container types to validate.
For example, to validate the List<String?> of a Map<String, List<String?>, we must write the following validation:
eachElement(String::class, NonEmptyList(1, 0)) {
notNull()
email()
//etc...
}