Hibernate 双向One-to-many 的问题

Question

new的Object是一个VO,不是被Hibernate管理的PO,而load来的就是;
1:
Parent p = new Parent ();
Child c = new Child();
c.setParent(p);
p.getChildren().add(c);
session.save(p);
session.flush();
照你这么写的,根本就只会插入parent的数据而已.child是否从session中load的?

Answer 1

有两个问题：
一、session.save(p)，这里应该是save many的对象还是one的对象？
如果是save one的对象，那么hibernate的那份reference有错？
如果是save many的对象，如果Parent的Child一下子增加多个，该怎么Save??书上的两种做法让我糊涂了！！二、你说的不是PO，但是经过session.save(p)处理它不是由VO变成PO了么？问题多多~~~~~~~~~~

Answer 2

贴出代码：
many的xml配置文件：
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 2.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd" >
    
<hibernate-mapping>
<!-- 
    Created by the Middlegen Hibernate plugin 2.1    http://boss.bekk.no/boss/middlegen/
    http://www.hibernate.org/
--><class 
    name="com.digipower.demo.vo.PCgCodeGVO" 
    table="P_CGCODE_G"
    dynamic-update="true"
    dynamic-insert="true"
>
    <meta attribute="class-description" inherit="false">
       @hibernate.class
        table="P_CGCODE_G" 
        dynamic-update="true"
        dynamic-insert="true"
    </meta>    <id
        name="pcgcodeGId"
        type="int"
        column="P_CGCODE_G_ID"
        unsaved-value="0"
    >
        <meta attribute="field-description">
           @hibernate.id
            generator-class="assigned"
            type="int"
            column="P_CGCODE_G_ID"
        </meta>
        <generator class="assigned" />
    </id>    <property
        name="adClientId"
        type="int"
        column="AD_CLIENT_ID"
        not-null="true"
        length="10"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="AD_CLIENT_ID"
            length="10"
            not-null="true"
        </meta>    
    </property>
    <property
        name="adOrgId"
        type="int"
        column="AD_ORG_ID"
        not-null="true"
        length="10"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="AD_ORG_ID"
            length="10"
            not-null="true"
        </meta>    
    </property>
    <property
        name="isactive"
        type="java.lang.String"
        column="ISACTIVE"
        not-null="true"
        length="1"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="ISACTIVE"
            length="1"
            not-null="true"
        </meta>    
    </property>
    <property
        name="created"
        type="java.sql.Timestamp"
        column="CREATED"
        not-null="true"
        length="7"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="CREATED"
            length="7"
            not-null="true"
        </meta>    
    </property>
    <property
        name="createdby"
        type="int"
        column="CREATEDBY"
        not-null="true"
        length="10"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="CREATEDBY"
            length="10"
            not-null="true"
        </meta>    
    </property>
    <property
        name="updated"
        type="java.sql.Timestamp"
        column="UPDATED"
        not-null="true"
        length="7"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="UPDATED"
            length="7"
            not-null="true"
        </meta>    
    </property>
    <property
        name="updatedby"
        type="int"
        column="UPDATEDBY"
        not-null="true"
        length="10"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="UPDATEDBY"
            length="10"
            not-null="true"
        </meta>    
    </property>
    <property
        name="cgvalue"
        type="java.lang.String"
        column="CGVALUE"
        not-null="true"
        length="80"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="CGVALUE"
            length="80"
            not-null="true"
        </meta>    
    </property>
    <property
        name="name"
        type="java.lang.String"
        column="NAME"
        not-null="true"
        length="120"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="NAME"
            length="120"
            not-null="true"
        </meta>    
    </property>
    <property
        name="location"
        type="java.lang.String"
        column="LOCATION"
        not-null="true"
        length="20"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="LOCATION"
            length="20"
            not-null="true"
        </meta>    
    </property>
    <property
        name="description"
        type="java.lang.String"
        column="DESCRIPTION"
        length="510"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="DESCRIPTION"
            length="510"
        </meta>    
    </property>
    <property
        name="help"
        type="java.lang.String"
        column="HELP"
        length="4000"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="HELP"
            length="4000"
        </meta>    
    </property>    <!-- Associations -->
  
    <!-- bi-directional one-to-many association to PcgcodeK -->
    <set
        name="pcgcodeKs"
        lazy="false"
        inverse="false"
        cascade="all"
    >
        <meta attribute="field-description">
           @hibernate.set
            lazy="false"
            inverse="false"
            cascade="all"           @hibernate.collection-key
            column="P_CGCODE_G_ID"           @hibernate.collection-one-to-many
            class="com.digipower.demo.vo.PCgCodeKVO"
        </meta>
        <key>
            <column name="P_CGCODE_G_ID" />
        </key>
        <one-to-many 
            class="com.digipower.demo.vo.PCgCodeKVO"
        />
    </set></class>
</hibernate-mapping>

Answer 3

One的xml:
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 2.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd" >
    
<hibernate-mapping>
<!-- 
    Created by the Middlegen Hibernate plugin 2.1    http://boss.bekk.no/boss/middlegen/
    http://www.hibernate.org/
--><class 
    name="com.digipower.demo.vo.PCgCodeKVO" 
    table="P_CGCODE_K"
    dynamic-update="false"
    dynamic-insert="false"
    batch-size="100"
>
    <meta attribute="class-description" inherit="false">
       @hibernate.class
        table="P_CGCODE_K"
        dynamic-update="false"
     dynamic-insert="false"
                batch-size="100"
    </meta>    <id
        name="pcgcodeKId"
        type="int"
        column="P_CGCODE_K_ID"
        unsaved-value="0"
    >
        <meta attribute="field-description">
           @hibernate.id
            generator-class="assigned"
            type="int"
            column="P_CGCODE_K_ID"
        </meta>
        <generator class="assigned" />
    </id>    <property
        name="adClientId"
        type="int"
        column="AD_CLIENT_ID"
        not-null="true"
        length="10"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="AD_CLIENT_ID"
            length="10"
            not-null="true"
        </meta>    
    </property>
    <property
        name="adOrgId"
        type="int"
        column="AD_ORG_ID"
        not-null="true"
        length="10"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="AD_ORG_ID"
            length="10"
            not-null="true"
        </meta>    
    </property>
    <property
        name="isactive"
        type="java.lang.String"
        column="ISACTIVE"
        not-null="true"
        length="1"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="ISACTIVE"
            length="1"
            not-null="true"
        </meta>    
    </property>
    <property
        name="created"
        type="java.sql.Timestamp"
        column="CREATED"
        not-null="true"
        length="7"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="CREATED"
            length="7"
            not-null="true"
        </meta>    
    </property>
    <property
        name="createdby"
        type="int"
        column="CREATEDBY"
        not-null="true"
        length="10"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="CREATEDBY"
            length="10"
            not-null="true"
        </meta>    
    </property>
    <property
        name="updated"
        type="java.sql.Timestamp"
        column="UPDATED"
        not-null="true"
        length="7"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="UPDATED"
            length="7"
            not-null="true"
        </meta>    
    </property>
    <property
        name="updatedby"
        type="int"
        column="UPDATEDBY"
        not-null="true"
        length="10"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="UPDATEDBY"
            length="10"
            not-null="true"
        </meta>    
    </property>
    <property
        name="cgvalue"
        type="java.lang.String"
        column="CGVALUE"
        not-null="true"
        length="80"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="CGVALUE"
            length="80"
            not-null="true"
        </meta>    
    </property>
    <property
        name="name"
        type="java.lang.String"
        column="NAME"
        not-null="true"
        length="120"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="NAME"
            length="120"
            not-null="true"
        </meta>    
    </property>
    <property
        name="location"
        type="java.lang.String"
        column="LOCATION"
        not-null="true"
        length="20"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="LOCATION"
            length="20"
            not-null="true"
        </meta>    
    </property>
    <property
        name="description"
        type="java.lang.String"
        column="DESCRIPTION"
        length="510"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="DESCRIPTION"
            length="510"
        </meta>    
    </property>
    <property
        name="help"
        type="java.lang.String"
        column="HELP"
        length="4000"
    >
        <meta attribute="field-description">
           @hibernate.property
            column="HELP"
            length="4000"
        </meta>    
    </property>    <!-- Associations -->
  
    <!-- bi-directional many-to-one association to PcgcodeG -->
    <many-to-one
        name="pCgCodeGVO"
        class="com.digipower.demo.vo.PCgCodeGVO"
        not-null="true"
  cascade="none"
outer-join="auto"
update="true"
insert="true"
access="property"
        column="P_CGCODE_G_ID"
    >
        <meta attribute="field-description">
           @hibernate.many-to-one
            not-null="true"
            update="true"
            insert="true"
             cascade="none"
outer-join="auto"
update="true"
insert="true"
access="property"
           @hibernate.column name="P_CGCODE_G_ID"         
        </meta>
        <column name="P_CGCODE_G_ID" />
    </many-to-one></class>
</hibernate-mapping>
存储代码：
  PCgCodeGVO gvo = new PCgCodeGVO();  /** 设置VO对象的主键值 */
  gvo.setPcgcodeGId(Integer.valueOf("1000"7));  PCgCodeKVO kvo = new PCgCodeKVO();
  
  kvo.setPcgcodeKId(Integer.valueOf("111"));  kvo.setpCgCodeGVO(gvo);
  gvo.getPcgcodeKs().add(kvo);  session.save(gvo);    //这里写成save(kvo)也不成两天了，郁闷死我了

Answer 4

汗,
Parent p = new Parent ();
p.setId()
Child c = new Child();
c.setParent(p);
p.getChildren().add(c);
session.save(p);
session.flush();
像这样写是正确的,会产生两条Insert语句,需要设置one这端cascade=all.
呵呵,没这样用过.

Answer 5

奇怪啊,不论是在one这端设置inverse="true",还是"false"都可以的,唯一区别就是one这端设置inverse="false"时会多一条更新many这端对象引用one主键的update的sql.以下测试过了,没问题.
Parent p = new Parent ();
p.setId("...")
Child c1 = new Child();
c1.setId("...");
c1.setParent(p);
Child c2 = new Child();
c2.setId("...");
c2.setParent(p);
p.getChildren().add(c1);
p.getChildren().add(c2);
session.save(p);
session.flush();

Answer 6

为什么我再用 save(gvo)的时候总是会是这样的呢？？Hibernate: insert into P_CGCODE_G (AD_CLIENT_ID, AD_ORG_ID, ISACTIVE, CREATED, CREATEDBY, UPDATED, UPDATEDBY, CGVALUE, NAME, LOCATION, DESCRIPTION, HELP, P_CGCODE_G_ID) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)Hibernate: update P_CGCODE_K set AD_CLIENT_ID=?, AD_ORG_ID=?, ISACTIVE=?, CREATED=?, CREATEDBY=?, UPDATED=?, UPDATEDBY=?, CGVALUE=?, NAME=?, LOCATION=?, DESCRIPTION=?, HELP=?, P_CGCODE_G_ID=? where P_CGCODE_K_ID=?GAction afterSave test对从表它总是只有一个update的sql，高手救救咱啊

Answer 7

嗯,应该是这样的,我使用的uuid.hex(但还是有点奇怪,我本来期待当parent主控时失败的.....)
而你的key策略是assigned,由parent主控,cascade=all,这样当你sessison.save(parent)时,hibernate发现其子的id不为null,于是认为这是一个PO,于是调用update语句更新所有child的状态.
事实上,应该让child主控的<set inverse="true" ....
然后:
//从其它层得到parent
session.save(parent);
//从其它层得到children
List children=....;
for (Iterator it = children.iterator(); it.hasNext();) {
  Child child=(Child)it.next();
  //这里的parent已经是一个po了,但事实上使用一个VO也成,cascade=none时,hibernate不会关心parent的状态的
  child.setParent(parent);
  session.save(child);
}
//这样作,应该是没有任何问题的,我一直都是这样用的.但你采用assigned时还是要小心一点,千万不要使用saveOrUpdate()

Answer 8

恩，谢谢楼上的老兄我得好好把hibernate reference  参考一下不知道楼上的兄台是怎么学hibernate的什么好的资料？

Answer 9

就是hibernate reference了,多写程序,碰到问题马上去查reference.