There is one further type of property mapping. The <any> mapping element defines a polymorphic association to classes from multiple tables. This type of mapping always requires more than one column. The first column holds the type of the associated entity. The remaining columns hold the identifier. It is impossible to specify a foreign key constraint for this kind of association, so this is most certainly not meant as the usual way of mapping (polymorphic) associations. You should use this only in very special cases (eg. audit logs, user session data, etc).

The meta-type attribute lets the application specify a custom type that maps database column values to persistent classes which have identifier properties of the type specified by id-type. You must specify the mapping from values of the meta-type to class names.

<any name="being" id-type="long" meta-type="string">
    <meta-value value="TBL_ANIMAL" class="Animal"/>
    <meta-value value="TBL_HUMAN" class="Human"/>
    <meta-value value="TBL_ALIEN" class="Alien"/>
    <column name="table_name"/>
    <column name="id"/>
</any>

<any
        name="propertyName"
        id-type="idtypename"
        meta-type="metatypename"
        cascade="cascade_style"
        access="field|property|ClassName"
        optimistic-lock="true|false"
>
        <meta-value ... />
        <meta-value ... />
        .....
        <column .... />
        <column .... />
        .....
</any>

name: the property name.

id-type: the identifier type.

meta-type (optional - defaults to string): Any type that is allowed for a discriminator mapping.

cascade (optional- defaults to none): the cascade style.

access (optional - defaults to property): The strategy Hibernate should use for accessing the property value.

optimistic-lock (optional - defaults to true): Specifies that updates to this property do or do not require acquisition of the optimistic lock. In other words, define if a version increment should occur if this property is dirty.