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== nullable



=== Purpose


Allows a property to be set to `null`. By default Grails does not allow `null` values for properties.


=== Examples


[source,groovy]
----
age nullable: true
----


=== Description


Set to `true` if the property allows `null` values.

This constraint influences  link:{hibernate5GuideFromRef}index.html#constraints[schema generation].

Error Code: `className.propertyName.nullable`

NOTE: Web requests resulting from form submissions will have blank strings, not `null`, for input fields that have no value. Keep this in mind when doing mass property binding to properties that are not nullable.  The default behavior is such that a blank string will not validate for `nullable: false` since the data binder will convert blank strings to null.  This includes empty strings and blank strings.  A blank string is any string such that the `trim()` method returns an empty string.  To turn off the conversion of empty strings to null set the `grails.databinding.convertEmptyStringsToNull` property to `false` in `application.groovy`. See the link:{guidePath}theWebLayer.html#dataBinding[data binding] section for more details on data binding.

[source,groovy]
.grails-app/conf/application.groovy
----

// the default value for this property is true
grails.databinding.convertEmptyStringsToNull = false

// ...
----

Or the equivalent in `grails-app/conf/application.yml`:

[source,yaml]
.grails-app/conf/application.yml
----

// the default value for this property is true
grails:
    databinding:
        convertEmptyStringsToNull: false

// ...
----
