io.helidon.validation (Helidon Project 4.4.0 API)

module io.helidon.validation

Helidon validation module.

Validation allows validating objects before they are used in business logic. This is achieved by either validating a type annotated with Validation.Validated, or by intercepting a method that has one of the constraint annotations (such as Validation.NotNull), or the Validation.Valid annotation to validate a type.

Constraints are implemented as services that implement the ConstraintValidator contract, and that are named with the fully qualified name of the constraint annotation. Build-in validators have lower than default weight, so they can be overridden by custom validators.

To enable validation of a type, it MUST be annotated with Validation.Validated, and Helidon declarative codegen must be on the annotation processor path. This will generate a type validator service.

To enable interception of validated methods, the method, its parameter, or a generic type argument must be annotated with one of the constraints in Validation class, or the Validation.Valid annotation, and the same codegen module must be on the annotation processor path.

The constraints are grouped (through container classes) based on types that can be constrained. Some constraints are for convenience - such as Validation.Integer.Max and Validation.Long.Max - this allows usage of properly typed constants, as the general number constraint Validation.Number.Max must use a String value (as it can be used for any number, ranging from Byte to a BigDecimal.

Object constraints

Any type can be annotated with (see details in the following list):

Validation.Valid - as long as the class/interface is Validation.Validated, will validate the instance (deep validation)
Validation.NotNull - will check that the value is not null
Validation.Null - will check that the value is null

String constraints

The following constraints can be used on String and CharSequence:

Validation.String.Length - minimal and/or maximal length
Validation.String.NotBlank - will check that the value is not blank
Validation.String.NotEmpty - will check that the value is not empty
Validation.String.Pattern - will check that the value matches the regular expression
Validation.String.Email - will check that the value matches e-mail structure

Integer constraints

The following constraints can be used on Integer, Long, Short, Byte, and Character:

Validation.Integer.Max - maximal value
Validation.Integer.Min - minimal value

Note that byte is always considered to be unsigned (i.e. values are from 0 to 255 inclusive).

Long constraints

The following constraints can be used ONLY on Long:

Validation.Long.Max - maximal value
Validation.Long.Min - minimal value

Number constraints

The following constraints can be used on Number and its implementations:

Validation.Number.Digits - max number of integer and fractional digits
Validation.Number.Max - maximal value
Validation.Number.Min - minimal value
Validation.Number.Negative - number must be negative (negative zero for longs is a zero)
Validation.Number.NegativeOrZero - number must not be positive
Validation.Number.Positive - number must be positive (zero is not positive)
Validation.Number.PositiveOrZero - number must be positive or zero (negative zero is OK)