[[chapter-bean-constraints]]
== Declaring and validating bean constraints

In this chapter you will learn how to declare (see <<section-declaring-bean-constraints>>) and
validate (see <<section-validating-bean-constraints>>) bean constraints.
<<section-builtin-constraints>> provides an overview of all built-in constraints coming with
Hibernate Validator.

If you are interested in applying constraints to method parameters and return values, refer to
<<chapter-method-constraints>>.

[[section-declaring-bean-constraints]]
=== Declaring bean constraints

Constraints in Bean Validation are expressed via Java annotations. In this section you will learn
how to enhance an object model with these annotations. There are the following three types of bean
constraints:

* field constraints
* property constraints
* class constraints

[NOTE]
====
Not all constraints can be placed on all of these levels. In fact, none of the default constraints
defined by Bean Validation can be placed at class level. The `java.lang.annotation.Target` annotation
in the constraint annotation itself determines on which elements a constraint can be placed. See
<<validator-customconstraints>> for more information.
====

==== Field-level constraints

Constraints can be expressed by annotating a field of a class. <<example-field-level>> shows a field
level configuration example:

[[example-field-level]]
.Field-level constraints
====
[source, JAVA]
----
package org.hibernate.validator.referenceguide.chapter02.fieldlevel;

public class Car {

	@NotNull
	private String manufacturer;

	@AssertTrue
	private boolean isRegistered;

	public Car(String manufacturer, boolean isRegistered) {
		this.manufacturer = manufacturer;
		this.isRegistered = isRegistered;
	}

	//getters and setters...
}
----
====

When using field-level constraints field access strategy is used to access the value to be
validated. This means the validation engine directly accesses the instance variable and does not
invoke the property accessor method even if such an accessor exists.

Constraints can be applied to fields of any access type (public, private etc.). Constraints on
static fields are not supported, though.

[TIP]
====
When validating byte code enhanced objects property level constraints should be used, because the
byte code enhancing library won't be able to determine a field access via reflection.
====

==== Property-level constraints

If your model class adheres to the
http://java.sun.com/javase/technologies/desktop/javabeans/index.jsp[JavaBeans] standard, it
is also possible to annotate the properties of a bean class instead of its fields.
<<example-property-level>> uses the same entity as in <<example-field-level>>, however, property level
constraints are used.

[[example-property-level]]
.Property-level constraints
====
[source, JAVA]
----
package org.hibernate.validator.referenceguide.chapter02.propertylevel;

public class Car {

	private String manufacturer;

	private boolean isRegistered;

	public Car(String manufacturer, boolean isRegistered) {
		this.manufacturer = manufacturer;
		this.isRegistered = isRegistered;
	}

	@NotNull
	public String getManufacturer() {
		return manufacturer;
	}

	public void setManufacturer(String manufacturer) {
		this.manufacturer = manufacturer;
	}

	@AssertTrue
	public boolean isRegistered() {
		return isRegistered;
	}

	public void setRegistered(boolean isRegistered) {
		this.isRegistered = isRegistered;
	}
}
----
====

[NOTE]
====
The property's getter method has to be annotated, not its setter. That way also read-only properties
can be constrained which have no setter method.
====

When using property level constraints property access strategy is used to access the value to be
validated, i.e. the validation engine accesses the state via the property accessor method.

[TIP]
====
It is recommended to stick either to field _or_ property annotations within one class. It is not
recommended to annotate a field _and_ the accompanying getter method as this would cause the field
to be validated twice.
====

[[type-arguments-constraints]]
==== Type argument constraints

Starting from Java 8, it is possible to specify constraints directly on the type argument of a
parameterized type. However, this requires that `ElementType.TYPE_USE` is specified via `@Target`
in the constraint definition. To maintain backwards compatibility, built-in Bean Validation as well as
Hibernate Validator specific constraints do not yet specify `ElementType.TYPE_USE`. To make use of
type argument constraints, custom constraints must be used (see <<validator-customconstraints>>).

Hibernate Validator validates type arguments constraints specified on collections, map values,
`java.util.Optional`, and custom parameterized types.

===== With `Iterable`

When applying constraints on an `Iterable` type argument, Hibernate Validator will validate each
element. <<example-type-arguments-constraints-collections>> shows an example of a
`List` with a type argument constraint.

In this example, `@ValidPart` is a custom constraint allowed to be used in the `TYPE_USE` context.

[[example-type-arguments-constraints-collections]]
.Type argument constraint on `List`
====
[source, JAVA]
----
package org.hibernate.validator.referenceguide.chapter02.typeargument;

public class Car {

	@Valid
	private List<@ValidPart String> parts = new ArrayList<>();

	public void addPart(String part) {
		parts.add( part );
	}

	//...
}
----

[source, JAVA]
----
Car car = Car();
car.addPart( "Wheel" );
car.addPart( null );

Set<ConstraintViolation<Car>> constraintViolations = validator.validate( car );

assertEquals( 1, constraintViolations.size() );
assertEquals(
		"'null' is not a valid car part.",
		constraintViolations.iterator().next().getMessage()
);
assertEquals( "parts[1].<collection element>",
		constraintViolations.iterator().next().getPropertyPath().toString() );
----
====

===== With `Map`

Type argument constraints are also validated for map values. Constraints on the key are ignored.
<<example-type-arguments-constraints-map>> shows an example of a `Map` value with a type
argument constraint.

[[example-type-arguments-constraints-map]]
.Type argument constraint on maps
====
[source, JAVA]
----
package org.hibernate.validator.referenceguide.chapter02.typeargument;

public class Car {

	public static enum FuelConsumption {
		CITY,
		HIGHWAY
	}

	@Valid
	private EnumMap<FuelConsumption, @MaxAllowedFuelConsumption Integer> fuelConsumption = new EnumMap<>( FuelConsumption.class );

	public void setFuelConsumption(FuelConsumption consumption, int value) {
		fuelConsumption.put( consumption, value );
	}

    //...
}

----

[source, JAVA]
----
Car car = new Car();
car.setFuelConsumption( Car.FuelConsumption.HIGHWAY, 20 );

Set<ConstraintViolation<Car>> constraintViolations = validator.validate( car );

assertEquals( 1, constraintViolations.size() );
assertEquals( "20 is outside the max fuel consumption.", constraintViolations.iterator().next().getMessage() );
----
====


===== With `java.util.Optional`

When applying a constraint on the type argument of `Optional`, Hibernate Validator will automatically
unwrap the type and validate the internal value. <<example-type-arguments-constraints-optional>> shows
an example of an `Optional` with a type argument constraint.

[[example-type-arguments-constraints-optional]]
.Type argument constraint on Optional
====
[source, JAVA]
----
package org.hibernate.validator.referenceguide.chapter02.typeargument;

import java.util.ArrayList;
import java.util.EnumMap;
import java.util.List;
import java.util.Optional;
import javax.validation.Valid;

public class Car {

	private Optional<@MinTowingCapacity(1000) Integer> towingCapacity = Optional.empty();

	public void setTowingCapacity(Integer alias) {
		towingCapacity = Optional.of( alias );
	}

    //...
}

----

[source, JAVA]
----
Car car = Car();
car.setTowingCapacity( 100 );

Set<ConstraintViolation<Car>> constraintViolations = validator.validate( car );

assertEquals( 1, constraintViolations.size() );
assertEquals( "Not enough towing capacity.", constraintViolations.iterator().next().getMessage() );
assertEquals( "towingCapacity", constraintViolations.iterator().next().getPropertyPath().toString() );
----
====


===== With custom parameterized types

Type arguments constraints can with two restrictions also be used with custom types. First, a
`ValidatedValueUnwrapper` must be registered for the custom type allowing to retrieve
the value to validate (see <<section-value-handling>>). Second, only types with one type arguments
are supported. Parameterized types with two or more type arguments are not checked for type argument
constraints. This limitation might change in future versions.

<<example-type-arguments-constraints-custom-parameterized-type>> shows an example of a custom
parameterized type with a type argument constraint.

[[example-type-arguments-constraints-custom-parameterized-type]]
.Type argument constraint on custom parameterized type
====
[source, JAVA]
----
package org.hibernate.validator.referenceguide.chapter02.typeargument;

public class Car {

	private GearBox<@MinTorque(100) Gear> gearBox;

	public void setGearBox(GearBox<Gear> gearBox) {
		this.gearBox = gearBox;
	}

	//...
}

----

[source, JAVA]
----
package org.hibernate.validator.referenceguide.chapter02.typeargument;

public class GearBox<T extends Gear> {

	private final T gear;

	public GearBox(T gear) {
		this.gear = gear;
	}

	public Gear getGear() {
		return this.gear;
	}
}
----

[source, JAVA]
----
package org.hibernate.validator.referenceguide.chapter02.typeargument;

public class Gear {
	private final Integer torque;

	public Gear(Integer torque) {
		this.torque = torque;
	}

	public Integer getTorque() {
		return torque;
	}

	public static class AcmeGear extends Gear {
		public AcmeGear() {
			super( 100 );
		}
	}
}
----

[source, JAVA]
----
package org.hibernate.validator.referenceguide.chapter02.typeargument;

public class GearBoxUnwrapper extends ValidatedValueUnwrapper<GearBox> {
	@Override
	public Object handleValidatedValue(GearBox gearBox) {
		return gearBox == null ? null : gearBox.getGear();
	}

	@Override
	public Type getValidatedValueType(Type valueType) {
		return Gear.class;
	}
}
----

[source, JAVA]
----
Car car = Car();
car.setGearBox( new GearBox<>( new Gear.AcmeGear() ) );

Set<ConstraintViolation<Car>> constraintViolations = validator.validate( car );
assertEquals( 1, constraintViolations.size() );
assertEquals( "Gear is not providing enough torque.", constraintViolations.iterator().next().getMessage() );
assertEquals( "gearBox", constraintViolations.iterator().next().getPropertyPath().toString() );
----
====


[[validator-usingvalidator-classlevel]]
==== Class-level constraints

Last but not least, a constraint can also be placed on the class level. In this case not a single
property is subject of the validation but the complete object. Class-level constraints are useful if
the validation depends on a correlation between several properties of an object.

The Car class in <<example-class-level>> has the two attributes `seatCount` and `passengers` and it
should be ensured that the list of passengers has not more entries than seats are available. For
that purpose the `@ValidPassengerCount` constraint is added on the class level. The validator of that
constraint has access to the complete `Car` object, allowing to compare the numbers of seats and
passengers.

Refer to <<section-class-level-constraints>> to learn in detail how to implement this custom
constraint.

[[example-class-level]]
.Class-level constraint
====
[source, JAVA]
----
package org.hibernate.validator.referenceguide.chapter02.classlevel;

@ValidPassengerCount
public class Car {

	private int seatCount;

	private List<Person> passengers;

	//...
}
----
====

[[section-constraint-inheritance]]
==== Constraint inheritance

When a class implements an interface or extends another class, all constraint annotations declared
on the super-type apply in the same manner as the constraints specified on the class itself. To make
things clearer let's have a look at the following example:

.Constraint inheritance
====
[source, JAVA]
----
package org.hibernate.validator.referenceguide.chapter02.inheritance;

public class Car {

	private String manufacturer;

	@NotNull
	public String getManufacturer() {
		return manufacturer;
	}

	//...
}
----

[source, JAVA]
----
package org.hibernate.validator.referenceguide.chapter02.inheritance;

public class RentalCar extends Car {

	private String rentalStation;

	@NotNull
	public String getRentalStation() {
		return rentalStation;
	}

	//...
}
----
====

Here the class `RentalCar` is a subclass of `Car` and adds the property `rentalStation`. If an instance of
`RentalCar` is validated, not only the `@NotNull` constraint on `rentalStation` is evaluated, but also the
constraint on `manufacturer` from the parent class.

The same would be true, if `Car` was not a superclass but an interface implemented by `RentalCar`.

Constraint annotations are aggregated if methods are overridden. So if `RentalCar` overrode the
`getManufacturer()` method from `Car`, any constraints annotated at the overriding method would be
evaluated in addition to the `@NotNull` constraint from the superclass.

[[section-object-graph-validation]]
==== Object graphs

The Bean Validation API does not only allow to validate single class instances but also complete
object graphs (cascaded validation). To do so, just annotate a field or property representing a
reference to another object with `@Valid` as demonstrated in <<example-cascaded-validation>>.

[[example-cascaded-validation]]
.Cascaded validation
====
[source, JAVA]
----
package org.hibernate.validator.referenceguide.chapter02.objectgraph;

public class Car {

	@NotNull
	@Valid
	private Person driver;

	//...
}
----

[source, JAVA]
----
package org.hibernate.validator.referenceguide.chapter02.objectgraph;

public class Person {

	@NotNull
	private String name;

	//...
}
----
====

If an instance of `Car` is validated, the referenced `Person` object will be validated as well, as the
`driver` field is annotated with `@Valid`. Therefore the validation of a `Car` will fail if the `name` field
of the referenced `Person` instance is `null`.

The validation of object graphs is recursive, i.e. if a reference marked for cascaded validation
points to an object which itself has properties annotated with `@Valid`, these references will be
followed up by the validation engine as well. The validation engine will ensure that no infinite
loops occur during cascaded validation, for example if two objects hold references to each other.

Note that `null` values are getting ignored during cascaded validation.

Object graph validation also works for collection-typed fields. That means any attributes that


* are arrays
* implement `java.lang.Iterable` (especially `Collection`, `List` and `Set`)
* implement `java.util.Map`

can be annotated with `@Valid`, which will cause each contained element to be validated, when the
parent object is validated.

[[example-cascaded-validation-list]]
.Cascaded validation of a collection
====
[source, JAVA]
----
package org.hibernate.validator.referenceguide.chapter02.objectgraph.list;

public class Car {

	@NotNull
	@Valid
	private List<Person> passengers = new ArrayList<Person>();

	//...
}
----
====

So when validating an instance of the `Car` class shown in <<example-cascaded-validation-list>>, a
`ConstraintViolation` will be created, if any of the `Person` objects contained in the passengers list
has a `null` name.

[[section-validating-bean-constraints]]
=== Validating bean constraints

The `Validator` interface is the most important object in Bean Validation. The next section shows how
to obtain an `Validator` instance. Afterwards you'll learn how to use the different methods of the
`Validator` interface.

[[section-obtaining-validator]]
==== Obtaining a `Validator` instance

The first step towards validating an entity instance is to get hold of a `Validator` instance. The
road to this instance leads via the `Validation` class and a `ValidatorFactory`. The easiest way is to
use the static method `Validation#buildDefaultValidatorFactory()`:

.`Validation#buildDefaultValidatorFactory()`
====
[source, JAVA]
----
ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
Validator validator = factory.getValidator();
----
====

This bootstraps a validator in the default configuration. Refer to <<chapter-bootstrapping>> to
learn more about the different bootstrapping methods and how to obtain a specifically configured
`Validator` instance.

==== Validator methods

The `Validator` interface contains three methods that can be used to either validate entire entities
or just single properties of the entity.

All three methods return a `Set<ConstraintViolation>`. The set is empty, if the validation succeeds.
Otherwise a `ConstraintViolation` instance is added for each violated constraint.

All the validation methods have a var-args parameter which can be used to specify, which validation
groups shall be considered when performing the validation. If the parameter is not specified the
default validation group (`javax.validation.groups.Default`) is used. The topic of validation groups
is discussed in detail in <<chapter-groups>>.

===== `Validator#validate()`

Use the `validate()` method to perform validation of all constraints of a given bean.
<<example-validator-validate>> shows the validation of an instance of the `Car` class from
<<example-property-level>> which fails to satisfy the `@NotNull` constraint on the `manufacturer`
property. The validation call therefore returns one `ConstraintViolation` object.

[[example-validator-validate]]
.Using `Validator#validate()`
====
[source, JAVA]
----
Car car = new Car( null, true );

Set<ConstraintViolation<Car>> constraintViolations = validator.validate( car );

assertEquals( 1, constraintViolations.size() );
assertEquals( "may not be null", constraintViolations.iterator().next().getMessage() );
----
====


===== `Validator#validateProperty()`

With help of the `validateProperty()` you can validate a single named property of a given object. The
property name is the JavaBeans property name.

.Using `Validator#validateProperty()`
====
[source, JAVA]
----
Car car = new Car( null, true );

Set<ConstraintViolation<Car>> constraintViolations = validator.validateProperty(
		car,
		"manufacturer"
);

assertEquals( 1, constraintViolations.size() );
assertEquals( "may not be null", constraintViolations.iterator().next().getMessage() );
----
====


===== `Validator#validateValue()`

By using the `validateValue()` method you can check whether a single property of a given class can be
validated successfully, if the property had the specified value:

.Using `Validator#validateValue()`
====
[source, JAVA]
----
Set<ConstraintViolation<Car>> constraintViolations = validator.validateValue(
		Car.class,
		"manufacturer",
		null
);

assertEquals( 1, constraintViolations.size() );
assertEquals( "may not be null", constraintViolations.iterator().next().getMessage() );
---

====

[NOTE]
====
`@Valid` is not honored by `validateProperty()` or `validateValue()`.
====


`Validator#validateProperty()` is for example used in the integration of Bean Validation into JSF 2
(see <<section-presentation-layer>>) to perform a validation of the values entered into a form
before they are propagated to the model.

[[section-constraint-violation-methods]]

==== `ConstraintViolation` methods

Now it is time to have a closer look at what a `ConstraintViolation` is. Using the different methods
of `ConstraintViolation` a lot of useful information about the cause of the validation failure can be
determined. <<table-constraint-violation>> gives an overview of these methods. The values in the
"Example" column refer to <<example-validator-validate>>.

[[table-constraint-violation]]
.The various `ConstraintViolation` methods
[options="header"]
|===============
|Method|Usage|Example
|`getMessage()`|The interpolated error message|"may not be null"
|`getMessageTemplate()`|The non-interpolated error message|"{... NotNull.message}"
|`getRootBean()`|The root bean being validated|car
|`getRootBeanClass()`|The class of the root bean being validated|`Car.class`
|`getLeafBean()`|If a bean constraint, the bean instance the constraint is
              applied on; If a property constraint, the bean instance hosting
              the property the constraint is applied on|`car`
|`getPropertyPath()`|The property path to the validated value from root
              bean|contains one node with kind
              `PROPERTY` and name "manufacturer"
|`getInvalidValue()`|The value failing to pass the constraint|`null`
|`getConstraintDescriptor()`|Constraint metadata reported to fail|descriptor for `@NotNull`

|===============


[[section-builtin-constraints]]
=== Built-in constraints

Hibernate Validator comprises a basic set of commonly used constraints. These are foremost the
constraints defined by the Bean Validation specification (see <<table-spec-constraints>>).
Additionally, Hibernate Validator provides useful custom constraints (see
<<table-custom-constraints>> and <<table-custom-country-constraints>>).

[[validator-defineconstraints-spec]]
==== Bean Validation constraints

<<table-spec-constraints>> shows purpose and supported data types of all constraints specified in
the Bean Validation API. All these constraints apply to the field/property level, there are no
class-level constraints defined in the Bean Validation specification. If you are using the Hibernate
object-relational mapper, some of the constraints are taken into account when creating the DDL for
your model (see column "Hibernate metadata impact").


[NOTE]
====
Hibernate Validator allows some constraints to be applied to more data types than required by the
Bean Validation specification (e.g. `@Max` can be applied to strings). Relying on this feature can
impact portability of your application between Bean Validation providers.
====


[[table-spec-constraints]]
.Bean Validation constraints
[options="header"]
|===============
|Annotation|Supported data types|Use|Hibernate metadata impact
|`@AssertFalse`|`Boolean`,
              `boolean`|Checks that the annotated element is
              false|None
|`@AssertTrue`|`Boolean`,
              `boolean`|Checks that the annotated element is
              true|None
|`@DecimalMax(value=,inclusive=)`|`BigDecimal`,
              `BigInteger`,
              `CharSequence`,
              `byte`, `short`,
              `int`, `long` and the
              respective wrappers of the primitive types; Additionally
              supported by HV: any sub-type of
              `Number`|Checks whether the annotated value is less than the
              specified maximum, when inclusive=false.
              Otherwise whether the value is less than or equal to the
              specified maximum. The parameter value is
              the string representation of the max value according to the
              `BigDecimal` string representation.|None
|`@DecimalMin(value=,inclusive=)`|`BigDecimal`,
              `BigInteger`,
              `CharSequence`,
              `byte`, `short`,
              `int`, `long` and the
              respective wrappers of the primitive types; Additionally
              supported by HV: any sub-type of
              `Number`|Checks whether the annotated value is larger than the
              specified minimum, when inclusive=false.
              Otherwise whether the value is larger than or equal to the
              specified minimum. The parameter value is
              the string representation of the min value according to the
              `BigDecimal` string representation.|None
|`@Digits(integer=,fraction=)`|BigDecimal,
              `BigInteger`,
              `CharSequence`,
              `byte`, `short`,
              `int`, `long` and the
              respective wrappers of the primitive types; Additionally
              supported by HV: any sub-type of
              `Number`|Checks whether the annotated value is a number having up to
              `integer` digits and
              `fraction` fractional digits|Defines column precision and scale
|`@Future`|`java.util.Date`,
              `java.util.Calendar`,
              `java.time.chrono.ChronoZonedDateTime`,
              `java.time.Instant`,
              `java.time.OffsetDateTime`; Additionally
              supported by HV, if the link:$$http://joda-time.sourceforge.net/$$[Joda Time]
              date/time API is on the class path: any implementations of
              `ReadablePartial` and
              `ReadableInstant`|Checks whether the annotated date is in the
              future|None
|`@Max(value=)`|`BigDecimal`,
              `BigInteger`, `byte`,
              `short`, `int`,
              `long` and the respective wrappers of the
              primitive types; Additionally supported by HV: any sub-type of
              `CharSequence` (the numeric value
              represented by the character sequence is evaluated), any
              sub-type of `Number`|Checks whether the annotated value is less than or equal
              to the specified maximum|Adds a check constraint on the column
|`@Min(value=)`|`BigDecimal`,
              `BigInteger`, `byte`,
              `short`, `int`,
              `long` and the respective wrappers of the
              primitive types; Additionally supported by HV: any sub-type of
              `CharSequence` (the numeric value
              represented by the char sequence is evaluated), any sub-type of
              `Number`|Checks whether the annotated value is higher than or
              equal to the specified minimum|Adds a check constraint on the column
|`@NotNull`|Any type|Checks that the annotated value is not
              `null`.|Column(s) are not nullable
|`@Null`|Any type|Checks that the annotated value is
              `null`|None
|`@Past`|`java.util.Date`,
              `java.util.Calendar`,
              `java.time.chrono.ChronoZonedDateTime`,
              `java.time.Instant`,
              `java.time.OffsetDateTime`; Additionally
              supported by HV, if the link:$$http://joda-time.sourceforge.net/$$[Joda Time]
              date/time API is on the class path: any implementations of
              `ReadablePartial` and
              `ReadableInstant`|Checks whether the annotated date is in the past|None
|`@Pattern(regex=,flag=)`|`CharSequence`|Checks if the annotated string matches the regular
              expression `regex` considering the given
              flag `match`|None
|`@Size(min=, max=)`|`CharSequence`,
              `Collection`, `Map`
              and arrays|Checks if the annotated element's size is between `min` and
              `max` (inclusive)|Column length will be set to
              `max`
|`@Valid`|Any non-primitive type|Performs validation recursively on the associated object.
              If the object is a collection or an array, the elements are
              validated recursively. If the object is a map, the value
              elements are validated recursively.|None

|===============



[NOTE]
====
On top of the parameters indicated in <<table-spec-constraints>> each constraint has the parameters
message, groups and payload. This is a requirement of the Bean Validation specification.
====


[[validator-defineconstraints-hv-constraints]]
==== Additional constraints

In addition to the constraints defined by the Bean Validation API Hibernate Validator provides
several useful custom constraints which are listed in <<table-custom-constraints>>. With one
exception also these constraints apply to the field/property level, only `@ScriptAssert` is a class-
level constraint.

[[table-custom-constraints]]
.Custom constraints
[cols="4*", options="header"]
|===============
|Annotation
|Supported data types
|Use
|Hibernate metadata impact

|`@CreditCardNumber(ignoreNonDigitCharacters=)`
|`CharSequence`
|Checks that the annotated character sequence passes the
 Luhn checksum test. Note, this validation aims to check for user
 mistakes, not credit card validity! See also
 http://www.merriampark.com/anatomycc.htm[Anatomy of Credit Card Numbers]. `ignoreNonDigitCharacters`
 allows to ignore non digit characters. The default is `false`.
|None

|`@EAN`
|`CharSequence`
|Checks that the annotated character sequence is a valid
link:$$http://en.wikipedia.org/wiki/International_Article_Number_%28EAN%29$$[EAN] barcode.
type determines the type of barcode. The default is EAN-13.
|None

|`@Email`
|`CharSequence`
|Checks whether the specified character sequence is a valid email address. The optional parameters
`regexp` and `flags` allow to specify an additional regular expression (including regular expression
flags) which the email must match.
|None

|`@Length(min=, +
         max=)`
|`CharSequence`
|Validates that the annotated character sequence is
              between `min` and
              `max` included
|Column length will be set to max

|`@LuhnCheck(startIndex= , +
            endIndex=, +
            checkDigitIndex=, +
            ignoreNonDigitCharacters=)`
|`CharSequence`
|Checks that the digits within the annotated character
sequence pass the Luhn checksum algorithm (see also
link:$$http://en.wikipedia.org/wiki/Luhn_algorithm$$[Luhn algorithm]). `startIndex` and
`endIndex` allow to only run the algorithm on
the specified sub-string. `checkDigitIndex`
allows to use an arbitrary digit within the character sequence
as the check digit. If not specified it is assumed that the
check digit is part of the specified range. Last but not least,
`ignoreNonDigitCharacters` allows to ignore
non digit characters.
|None

|`@Mod10Check(multiplier=, +
             weight=, +
             startIndex=, +
             endIndex=, +
             checkDigitIndex=, +
             ignoreNonDigitCharacters=)`
|`CharSequence`
|Checks that the digits within the annotated character
sequence pass the generic mod 10 checksum algorithm.
`multiplier` determines the multiplier for
odd numbers (defaults to 3), `weight` the
weight for even numbers (defaults to 1).
`startIndex` and
`endIndex` allow to only run the algorithm on
the specified sub-string. `checkDigitIndex`
allows to use an arbitrary digit within the character sequence
as the check digit. If not specified it is assumed that the
check digit is part of the specified range. Last but not least,
`ignoreNonDigitCharacters` allows to ignore
non digit characters.
|None

|`@Mod11Check(threshold=, +
             startIndex=, +
             endIndex=, +
             checkDigitIndex=, +
             ignoreNonDigitCharacters=, +
             treatCheck10As=, +
             treatCheck11As=)`
|`CharSequence`
|Checks that the digits within the annotated character
sequence pass the mod 11 checksum algorithm.
`threshold` specifies the threshold for the
mod11 multiplier growth; if no value is specified the multiplier
will grow indefinitely. `treatCheck10As`
and `treatCheck11As` specify the check
digits to be used when the mod 11 checksum equals 10 or 11,
respectively. Default to X and 0, respectively.
`startIndex`, `endIndex`
`checkDigitIndex` and
`ignoreNonDigitCharacters` carry the same
semantics as in `@Mod10Check`.
|None

|`@NotBlank`
|`CharSequence`
|Checks that the annotated character sequence is not null
and the trimmed length is greater than 0. The difference to
`@NotEmpty` is that this constraint can
only be applied on strings and that trailing white-spaces are
ignored.
|None

|`@NotEmpty`
|`CharSequence`, `Collection`, `Map` and arrays
|Checks whether the annotated element is not null nor empty
|None

|`@Range(min=, +
        max=)`
|`BigDecimal`, `BigInteger`, `CharSequence`, `byte`, `short`, `int`, `long` and the respective wrappers of the
primitive types
|Checks whether the annotated value lies between (inclusive) the specified minimum and maximum
|None

|`@SafeHtml(whitelistType= , +
           additionalTags=, +
           additionalTagsWithAttributes=)`
|`CharSequence`
|Checks whether the annotated value
contains potentially malicious fragments such as `<script/>`. In order to use this
constraint, the
link:$$http://jsoup.org/$$[jsoup] library must be part of the class path.
With the `whitelistType` attribute a predefined whitelist type can be chosen which can
be refined via `additionalTags` or `additionalTagsWithAttributes`. The former allows to
add tags without any attributes, whereas the latter allows to specify tags and
optionally allowed attributes using the annotation `@SafeHtml.Tag`.
|None

|`@ScriptAssert(lang=, +
              script=, +
              alias=)`
|Any type
|Checks whether the given script can successfully be
evaluated against the annotated element. In order to use this
constraint, an implementation of the Java Scripting API as
defined by JSR 223 ("Scripting for the
Java^TM^ Platform") must part of the
class path. The expressions to be evaluated can be written in
any scripting or expression language, for which a JSR 223
compatible engine can be found in the class path.
|None

|`@URL(protocol=, +
      host=, +
      port=, +
      regexp=, +
      flags=)`
|`CharSequence`
|Checks if the annotated character sequence is a valid URL
according to RFC2396. If any of the optional parameters
`protocol`, `host` or
`port` are specified, the corresponding URL
fragments must match the specified values. The optional
parameters `regexp` and
`flags` allow to specify an additional
regular expression (including regular expression flags) which
the URL must match. Per default this constraint used the `java.net.URL` constructor to
verify whether a given string represents a valid URL. A regular expression based version is also
available - `RegexpURLValidator` - which can be configured via XML
(see <<section-mapping-xml-constraints>>) or the programmatic API
(see <<section-programmatic-constraint-definition>>).
|None

|===============




===== Country specific constraints

Hibernate Validator offers also some country specific constraints, e.g. for the validation of social
security numbers.

[NOTE]
====
If you have to implement a country specific constraint, consider making it a contribution to
Hibernate Validator!
====


[[table-custom-country-constraints]]
.Custom country specific constraints
[options="header"]
|===============
|Annotation|Supported data types|Use|Country|Hibernate metadata impact
|`@CNPJ`|`CharSequence`|Checks that the annotated character sequence represents
                a Brazilian corporate tax payer registry number (Cadastro de
                Pessoa Juríeddica)|Brazil|None
|`@CPF`|`CharSequence`|Checks that the annotated character sequence represents
                a Brazilian individual taxpayer registry number (Cadastro de
                Pessoa Fídsica)|Brazil|None
|`@TituloEleitoral`|`CharSequence`|Checks that the annotated character sequence represents
                a Brazilian voter ID card number (link:$$http://ghiorzi.org/cgcancpf.htm$$[Título Eleitoral])|Brazil|None

|===============



[TIP]
====
In some cases neither the Bean Validation constraints nor the custom constraints provided by
Hibernate Validator will fulfill your requirements. In this case you can easily write your own
constraint. You can find more information in <<validator-customconstraints>>.
====


