Package com.orchestranetworks.schema

# Interface ConstraintOnNull

All Superinterfaces:
  `JavaBeanVersion`

public interface ConstraintOnNull extends JavaBeanVersion
Defines a verification for values that are mandatory under certain circumstances.

### Data model definition and life cycle

Any implementation of this interface must also implement the `Constraint` interface. As such, its data model declaration and its life cycle are the same as `Constraint`.

### Restriction policy

As this interface serves as a restriction of the static data model constraint `minOccurs`, the method `checkNull(ValueContextForValidation)` is only called under the following conditions:

Data model definition | Perform `checkNull()`
`minOccurs="0"` and `maxOccurs="1"` | If no value is defined (`null`) and the dataset is activated
`minOccurs > 0` | No
`maxOccurs > 1` | No

NOTE: By default, constraints on null value are not checked on user input. In order to enable this check, the `osd:checkNullInput` property must be set and if the element is terminal, the dataset must also be activated.

See Also:
  - `Constraint`
  - `JavaBeanVersion.getBeanVersion()`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `checkNull(ValueContextForValidation aValidationContext)`
  This method performs a check when no value is defined; adds error message if necessary.

  ### Methods inherited from interface com.orchestranetworks.schema.JavaBeanVersion

  `getBeanVersion`

- ## Method Details

  - ### checkNull

    void checkNull(ValueContextForValidation aValidationContext) throws InvalidSchemaException
    This method performs a check when no value is defined; adds error message if necessary.
    Parameters:
      `aValidationContext` - the context
    Throws:
      `InvalidSchemaException` - if a dynamic condition in the data model prevents the execution of this method.