Rule Definition
Hibernate supports this usage; indeed, the details of an array mapping are virtually identical to those of a list. However, we very strongly recommend against the use of arrays, since arrays can't be lazily initialized (there is no way to proxy an array at the virtual machine level). Lists, maps and sets are the most efficient collection types. So, using array can affect your application performance when it can contain many items, it looses lazy loading, optimized dirty checking and performance features for persistent collections.

Remediation
Use lists, maps, bags, idbags and sets depending on your case.

Violation Code Sample

<hibernate-mapping >
  
  <class name="A" table ="A">
    <id name="id" column="A_ID">
      <generator class="increment"/>
    </id>
     <array name="Bitems" cascade="all" fetch="join"> // VIOLATION
      <key column="A_ID"/>
      <one-to-many class="B"/>
    </array>
  </class>

  <class name="B" table="B" lazy="true">
    <id name="id" column="B_ID">
      <generator class="increment"/>
    </id>
  </class>

</hibernate-mapping

Fixed Code Sample

<hibernate-mapping >
  
  <class name="A" table ="A"> 
    <id name="id">
      <generator class="increment"/>
    </id>

    // FIXED with a list (it could have been set, map, idbag or bag)
    <list name="Bitems" cascade="all" fetch="join"> 
      <key column="B_ID"/>
      <list-index column="ID"/>
      <one-to-many class="B"/>
    </array>
  </class>

  <class name="B" table="B" lazy="true">
    <id name="id" column="B_ID">
      <generator class="increment"/>
    </id>
  </class>

</hibernate-mapping>

Hibernate in Action (ISBN 1932394-15-X) p 214 http://srcrr.com/java/hibernate/3.6.2/reference/org/hibernate/collection/PersistentArrayHolder.html