<hibernate-mapping>
   <class name="my.package.Document" table="document">
      <id name="id" column="id">
         <generator class="native"/>
      </id>
      <property name="name"/>
      <property name="created"/>
      <property name="updated"/>
      <property name="location"/>
        <many-to-one name="owner" class="my.package.User" not-null="true"/>
      <property name="contentType"/>
      <property name="size"/>
      <many-to-one name="parent" class="my.package.Document"/>
      <property name="parent"/>
      <property name="directory"/>
   </class>
</hibernate-mapping>

public class Document {   
       
    private Integer id = 0;
    private String name = null;
    private Date created = null;
    private Date updated = null;
    private File file = null;
    private long size = 0;
    private User owner = null;
    private String contentType = CONTENT_TYPE_UNDEF;
    private Document parent = null;
    private boolean directory = false;

... getters and setters

org.hibernate.MappingException: Could not determine type for: my.package.Document, for columns: [org.hibernate.mapping.Column(parent)]
   at org.hibernate.mapping.SimpleValue.getType(SimpleValue.java:266)
   at org.hibernate.mapping.SimpleValue.isValid(SimpleValue.java:253)

      <many-to-one name="parent" class="my.package.Document"/>
      <property name="parent"/>