hibernate中Map类型的双向一对多映射

　这几天一直在郁闷hibernate中关于Map类型的一对多关系做映射的问题，参照Set的映射貌似可以存储，但是加载的时候就报错了！由于这几天一直呆在家里，用一个仅仅256kb/s的移动TD网卡上网（打开一个网页都要半个小时，而且是按照流量收费的），所以没有上网查，参照动力节点王勇老师讲的Set的映射方法和网上的方法，自己杜撰了一种方法（姑且称为桂式方法），弄了很长时间没弄好，所以只好放弃！今天回学校了，上网认真查了查，再在群里面问了问，总算是把问题基本上解决了！

参照过的觉得最有帮助的一篇文章出处是：http://esffor.iteye.com/blog/168253

有两个类：MapLayer和MapLayerField

package com.hgTIS.webgis.model;
import java.util.LinkedHashMap;
import java.util.Map;

/**
 * PointLayer generated by MyEclipse - Hibernate Tools
 */

public class MapLayer  implements java.io.Serializable {

    /**图层id**/
    private Long id;

    /**图层英文名称，动态图层与数据库标明一致，静态图层与图片名称一致**/
     private String name;
     /**图层中文名称**/
     private String chName;
    
     /**是否显示**/
     private String display;
     /**图层叠加次序**/
     private Integer placeOrder;
     /**最小比例等级**/
     private String minScale;
     /**最大比例等级**/
     private String maxScale;
    
     /**图层类型.point/layer/polygon**/
     private String feaType;
     /**图层类型:1动态;2静态;3空间查询;**/
     private String type;
    
     /**坐标系统**/
    private String coordinateSystem;
    /**父类图层ID；静态图层空间查询的时候使用**/
    private MapLayer parentLayer;

    /**必须用的字段**/
    private Map<String,MapLayerField> displayFields =new LinkedHashMap<String, MapLayerField>(0);
    /**分类显示的字段**/
    private String sortField;
/**
　　　　geters and seters
**/
}

MapLayerField.java

package com.hgTIS.webgis.model;


/**
 * 图层字段对象
 */

public class MapLayerField  implements java.io.Serializable {


    /**唯一标识**/
     private Long id;
    
     /**字段名称，一般与数据库字段一致**/
     private String name;
    
     /**中文名称**/
     private String chName;
    
     /**是否系统字段**/
     private String systemField;
    
     /**是否显示字段**/
     private String viewField;
    
     /**是否分类字段**/
     private String sortField;

     /**标题字段**/
     private String titleField;
    
     /**次序**/
     private Integer forder;
 
     private MapLayer mapLayer;

/**
　　　　geters and seters
**/
}

xml文件
MapLayer.hbm.xml

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!--
    Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
    <class name="com.hgTIS.webgis.model.MapLayer" table="mapLayer" >
        <id name="id" type="long">
            <column name="id" />
            <generator class="native"/>
        </id>
        <property name="name" column="name" not-null="true"/>
        <property name="chName" column="chName"/>
        <property name="display" column="display"/>
        <property name="placeOrder" column="placeOrder"/>
        <property name="minScale" column="minScale"/>
        <property name="maxScale" column="maxScale"/>
        <property name="feaType" column="feaType"/>
        <property name="type" column="type"/>
        <property name="coordinateSystem" column="coordinateSystem"/>
        <many-to-one name="parentLayer" column="parentLayerId"/>
        <property name="sortField" column="sortField"/>
        <map name="displayFields" inverse="true" cascade="all">
            <key column="layerid"/>
            <map-key type="string" column="name"/><!--  上面引用的那篇文章说index标签也可以-->
            <one-to-many class="com.hgTIS.webgis.model.MapLayerField"/>
        </map>
    </class>
</hibernate-mapping>

MapLayerField.hbm.xml

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 
    Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
    <class name="com.hgTIS.webgis.model.MapLayerField" table="mapLayerField" >
        <id name="id" type="long">
            <column name="id" />
            <generator class="native" />
        </id>
        <property name="name" column="name" not-null="true"/>
        <property name="chName" column="chName"/>
        <property name="systemField" column="systemField"/>
        <property name="viewField" column="viewField"/>
        <property name="sortField" column="sortField"/>
        <property name="titleField" column="titleField"/>
        <property name="forder" column="forder"/>
        <many-to-one name="mapLayer" column="layerid"/>
    </class>
</hibernate-mapping>

主要是映射文件中的map标签中的map-key标签一定要与相应的类中的属性一致！