org.hibernate.PropertyValueException: not-null property references a null or transient value

org.hibernate.PropertyValueException: not-null property references a null or transient value:

com.bjcx.project.entity.task.Equipmenttable.ProjPortfolioID 
at org.hibernate.engine.Nullability.checkNullability(Nullability.java:72) 
at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate 

字面意思：一个不允许为Null的属性引用了一个为Null的或者无效的值。 

原因：在***.hbm.xml中的 

<property name="ProjPortfolioID" column="ProjPortfolioID" 
    type="big_decimal" not-null="true" length="10" /> 

中，not-null="true",这说明属性ProjPortfolioID 不允许为空，而在ActionForm中未给他赋值，则就为空，所以就会报错！

source:http://zgphacker2010.iteye.com/blog/983190