Hibernate之deleted object would be re-saved by cascade异常

Hibernate之deleted object would be re-saved by cascade异常

在Hibernate中，删除存在关联关系的一个对象时，会出现 org.hibernate.ObjectDeletedException: deleted object would be re-saved by cascade (remove deleted object from associations)这个异常

如下：
持久化类：

import  java.util.HashSet;
import  java.util.Set;

import  org.apache.commons.lang.builder.EqualsBuilder;
import  org.apache.commons.lang.builder.HashCodeBuilder;
import  org.apache.commons.lang.builder.ToStringBuilder;

/**
 * 产品类别对象
 *  @author  crazycy
 *
  */
public   class  ProductCategory  extends  BaseObject {

     //  Fields    

     private   long  id;

     private  String name;

     private  String description;

     private  ProductCategory parentCategory;

     private  Set childrenCategories  =   new  HashSet();

     //  Constructors

     /**  default constructor  */
     public  ProductCategory() {
    }

     /**  minimal constructor  */
     public  ProductCategory(String name) {
         this .name  =  name;
    }
    
     public  ProductCategory(String name, String description) {
         this .name  =  name;
         this .description  =  description;
    }

     /**  full constructor  */
     public  ProductCategory(String name, String description,
            ProductCategory parentCategory) {
         this .name  =  name;
         this .description  =  description;
         this .parentCategory  =  parentCategory;
    }

     /**  full constructor  */
     public  ProductCategory(String name, String description,
            Set childrenCategories) {
         this .name  =  name;
         this .description  =  description;
         this .childrenCategories  =  childrenCategories;
    }

     //  Property accessors

     public   long  getId() {
         return   this .id;
    }

     public   void  setId( long  id) {
         this .id  =  id;
    }

     public  String getName() {
         return   this .name;
    }

     public   void  setName(String name) {
         this .name  =  name;
    }

     public  String getDescription() {
         return   this .description;
    }

     public   void  setDescription(String description) {
         this .description  =  description;
    }

     public  ProductCategory getParentCategory() {
         return   this .parentCategory;
    }

     public   void  setParentCategory(ProductCategory parentCategory) {
         this .parentCategory  =  parentCategory;
    }
    
     /**
     * 由主来调：是主添加
     *  @param  productCategory
      */
     public   void  addCategory(ProductCategory productCategory) {
        productCategory.setParentCategory( this );
        childrenCategories.add(productCategory);
    }
    
     /**
     * 由主来调；是从主删除
     *  @param  productCategory
      */
     public   void  removeCategory(ProductCategory productCategory) {
        childrenCategories.remove(productCategory);
        productCategory.setParentCategory( null );
    }
    
     public  Set getChildrenCategories() {
         return  childrenCategories;
    }

     public   void  setChildrenCategories(Set childrenCategories) {
         this .childrenCategories  =  childrenCategories;
    }

     /**
     *  @see  java.lang.Object#equals(Object)
      */
     public   boolean  equals(Object object) {
         if  ( ! (object  instanceof  ProductCategory)) {
             return   false ;
        }
        ProductCategory rhs  =  (ProductCategory) object;
         return   new  EqualsBuilder().append( this .description, rhs.description)
                .append( this .name, rhs.name).append( this .id, rhs.id).isEquals();
    }

     /**
     *  @see  java.lang.Object#hashCode()
      */
     public   int  hashCode() {
         return   new  HashCodeBuilder( 1009592109 ,  - 669108101 ).append(
                 this .description).append( this .name).append( this .id)
                .toHashCode();
    }

     /**
     *  @see  java.lang.Object#toString()
      */
     public  String toString() {
         return   new  ToStringBuilder( this ).append( " name " ,  this .name).append(
                 " description " ,  this .description).append( " id " ,  this .id)
                .toString();
    }

}

映射文件

<? xml version = " 1.0 " ?>
<! DOCTYPE hibernate - mapping PUBLIC  " -//Hibernate/Hibernate Mapping DTD 3.0//EN "
" http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd " >

< hibernate - mapping  package = " " >
     < class  name = " ProductCategory "  table = " productcategory " >
         < id name = " id "  type = " long " >
             < column name = " ID "   />
             < generator  class = " native "   />
         </ id >
         < property name = " name "  type = " string " >
             < column name = " name "  length = " 50 "  not - null = " true "   />
         </ property >
         < property name = " description "  type = " string " >
             < column name = " description "  length = " 150 "   />
         </ property >
         < set name = " childrenCategories "  cascade = " save-update "  inverse = " true " >
             < key column = " parent " />
             < one - to - many  class = " ProductCategory " />
         </ set >
         < many - to - one name = " parentCategory "  column = " parent "  
             class = " ProductCategory "  
            cascade = " save-update "
          >
         </ many - to - one >
     </ class >
</ hibernate - mapping >

测试代码：

category2.getChildrenCategories().remove(category5);
        category5.setParentCategory( null );
        dao.removeProductCategory(category5.getId());

解决方案如下：
方法1 删除Set方的cascade
方法2 解决关联关系后，再删除 :

category2.getChildrenCategories().remove(category5);
        category5.setParentCategory( null );
        dao.removeProductCategory(category5.getId());

方法3 在many-to-one方增加cascade 但值不能是none

如果以上三个方案都失败（哼哼~ 我用了5个小时才找出来的）
检查一下hashCode equals是否使用了id作为唯一标示的选项了；我用uuid.hex时是没有问题的；
但是用了native，就不行了，怎么办？删除啊！

也就是问题出现在本文给出的持久化类的hashCode equals方法身上