Hibernate映射求助！

Question

<class name=" " table="">
        <id name="id" column="ID" unsaved-value="0">
            <generator class="increment"/>
        </id>
        <property name="title">
            <column name="Title" length="16" not-null="true"/>
        </property>
        <many-to-one name="PID"column="PID" class=" "/>         
    </class>

Answer 1

<class name="mypack.Category" table="CATEGORIES" >
    <id name="id" type="long" column="ID">
      <generator class="increment"/>
    </id>    <property name="name" type="string" >
        <column name="NAME" length="15" />
    </property>    <set 
        name="childCategories"
        cascade="save-update"
        inverse="true"
        >
        <key column="CATEGORY_ID" />
        <one-to-many class="mypack.Category" />
     </set>      <many-to-one
        name="parentCategory"
        column="CATEGORY_ID"
        class="mypack.Category"
       />  </class>