Module jakarta.data
Package jakarta.data.constraint

Interface Null<V>

Type Parameters:
V - type of the entity attribute or a subtype or primitive wrapper type for the entity attribute.
All Superinterfaces:
Constraint<V>
public interface Null<V> extends Constraint<V>

A constraint that requires a null value.

A parameter-based repository method can impose a constraint on an entity attribute by defining a method parameter that is of type Null. For example,


 @Find
 List<Car> ofUnknownModel(@By(_Car.MAKE) String make,
                          @By(_Car.MODEL) Null<String> nullModel);
 ...

 found = cars.ofUnknownModel("Jakarta Motors",
                             Null.instance());

Repository methods can also accept Null constraints at run time in the form of a Restriction on an Expression. For example, 


 @Find
 List<Car> searchAll(Restriction<Car> restrict, Order<Car> sorts);

 ...

 found = cars.searchAll(Restrict.all(_Car.make.equalTo("Jakarta Motors"),
                                     _Car.model.isNull()),
                        Order.by(_Car.year.desc(),
                                 _Car.price.asc()));

The entity and static metamodel for the code examples within this class are shown in the Attribute Javadoc.

Since:
1.1

  • Method Summary

    Static Methods
    Modifier and Type
    Method
    Description
    static <V> Null<V>
    instance()
    Requires that the constraint target has a null value.

    Methods inherited from interface jakarta.data.constraint.Constraint

    negate

  • Method Details

    • instance

      static <V> Null<V> instance()

      Requires that the constraint target has a null value. For example,

      
     found = cars.ofMakeAndModel("Jakarta Motors",
                                 Null.instance());
      Type Parameters:
      V - type of the entity attribute or a subtype or primitive wrapper type for the entity attribute.
      Returns:
      a Null constraint.