/** superclass (or make it an interface if you want) for all your domain classes
* that should be "flagged/soft" deleted when deleted instead of "hard" deleted.
*/
public class SoftDeletable {
    private Boolean deleted;
....
}

/** plug this listener into hibernate (config below) */
public class SoftDeleteEventListener extends DefaultDeleteEventListener
    public void onDelete(DeleteEvent event) {
        Object toDelete = event.getObject();   

        // "soft delete" objects that inherit this behaviour
        if( toDelete instanceof SoftDeletable ) {
            Session session = event.getSession();
           
            // set delete-flag and update object.
            (( toDelete ) SoftDeletable).setDeleted( Boolean.TRUE );
            session.update( toDelete );
        } else {
            // Proceed with normal delete for other objects
            super.onDelete( event );
        }
    }
}

<hibernate-configuration>
    <session-factory>
        ...
        <event type="delete">
            <listener class="foo.bar.SoftDeleteEventListener"/>
        </event>
    </session-factory>
</hibernate-configuration>