Hibernate 外键约束问题

最新推荐文章于 2024-02-18 16:42:47 发布

原创最新推荐文章于 2024-02-18 16:42:47 发布 · 6.6k 阅读

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文章标签：

#hibernate #integer #cmm #string #generator #class

本文探讨了在Hibernate配置中，1对多关系中外键约束的重要性。错误地设置inverse属性可能导致找不到主键的错误。举例说明了Machine和PositionMachine之间的关系，强调了inverse属性设置正确与否对数据更新控制的影响。

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Hibernate 配置中,

对于有 1 对多的外键约束关系, 如果把inverse 属性设置反了的话 ,

就有可能找不到出现找不到主键的错误

比如一太机器对应多个岗位的问题

Machine.hbm.xml 如下

<?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>
    <class name="com.novemsoft.model.Machine" table="CMM_MCHN" lazy="false">
        <id name="id" type="integer">
            <column name="MCHN_KEY" />
            <generator class="increment" />
        </id>
        <property name="name" type="string">
            <column name="MCHN_NAME" length="30" />
        </property>
        <property name="enname" type="string">
            <column name="MCHN_ENG_NAME" length="30" />
        </property>
        <property name="code" type="string">
            <column name="MCHN_CODE " length="30" />
        </property>
        
        <property name="beginDate" type="timestamp">
            <column name="MCHN_BGN_DATE" length="19" />
        </property>
        <property name="endDate" type="timestamp">
            <column name="MCHN_END_DATE" length="19" />
        </property>
        <property name="status" type="int">
            <column name="MCHN_STS_CODE"/>
        </property>

        <set name="cmm_pstn_mchn" inverse="true" cascade="all" lazy="false">
        <key column="MCHN_KEY"></key>
        <one-to-many class="com.novemsoft.model.PositionMachine"/>
        </set>

        <!--  here if we set the inverse = false, than we can't update the positionMachine table when

we use session.saveOrUpdate(Machine); in other words here inverse =true mean let the machine side to control the update , if the inverse=false let the positionMachine side to control update

-->
</class>
</hibernate-mapping>

PositionMachine.hbm.xml as following

<?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>
<class name="com.novemsoft.model.PositionMachine" table="cmm_pstn_mchn">
  <id name="id" type="integer">
            <column name="PSTN_MCHN_KEY" />
            <generator class="increment" />
        </id>

        <many-to-one name="cmm_mchn" class="com.novemsoft.model.Machine" column="MCHN_KEY" lazy="false">
        </many-to-one>

        <many-to-one name="cmm_pstn" class="com.novemsoft.model.Position" column="PSTN_KEY" lazy="false">
        </many-to-one>

        
</class>
</hibernate-mapping>