4.2.2.4. Meta-Annotations

Entity meta-annotations are a set of key/value pairs providing additional information about entities.

Meta-annotations are accessed using meta-class getAnnotations() method.

The sources of meta-annotations are:

  • @OnDelete, @OnDeleteInverse, @Extends annotations. These annotations cause creation of special meta-annotations for describing relations between entities.

  • Extendable meta-annotations marked with @MetaAnnotation. These annotations are converted to meta-annotations with a key corresponding to the full name of Java class of the annotation and a value which is a map of annotation attributes. For example, @TrackEditScreenHistory annotation will have a value which is a map with a single entry: value → true. The platform provides the following annotations of this kind: @NamePattern, @SystemLevel, @EnableRestore, @TrackEditScreenHistory. In your application or application components, you can create your own annotation classes and mark them with @MetaAnnotation annotation.

  • Optional: entity meta-annotations can also be defined in metadata.xml files. If a meta-annotation in XML has the same name as the meta-annotation created by Java entity class annotation, then it will override the latter.

    The example below shows how to override meta-annotations in metadata.xml:

    <metadata xmlns="http://schemas.haulmont.com/cuba/metadata.xsd">
    <!-- ... -->

    <annotations>
        <entity class="com.company.customers.entity.Customer">
            <annotation name="com.haulmont.cuba.core.entity.annotation.TrackEditScreenHistory">
                <attribute name="value" value="true" datatype="boolean"/>
            </annotation>

            <property name="name">
                <annotation name="length" value="200"/>
            </property>

            <property name="customerGroup">
                <annotation name="com.haulmont.cuba.core.entity.annotation.Lookup">
                    <attribute name="type" class="com.haulmont.cuba.core.entity.annotation.LookupType" value="DROPDOWN"/>
                    <attribute name="actions" datatype="string">
                        <value>lookup</value>
                        <value>open</value>
                    </attribute>
                </annotation>
            </property>
        </entity>

        <entity class="com.company.customers.entity.CustomerGroup">
            <annotation name="com.haulmont.cuba.core.entity.annotation.EnableRestore">
                <attribute name="value" value="false" datatype="boolean"/>
            </annotation>
        </entity>
    </annotations>
</metadata>