Attribute "out-join" must be declared for element type "many-to-one"该如何解决

Attribute "out-join" must be declared for element type "many-to-one".
<many-to-one name="id" out-join="true"
class="com.xxx.xxx.xx.xxx" 
not-null="true" lazy="false">
<column name="XXX" />
</many-to-one>
加载就出现了Attribute "out-join" must be declared for element type "many-to-one". 不知何故？
------解决方案--------------------
该问题问的比较2.。。自己结贴~