Hibernate映射mysql问题 one-to-one

当我们使用hibernate的一对一映射，配置mysql数据库表时：

两表的配置文件如下：

1、tseal:

<?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">

<hibernate-mapping>

<class name="com.indigopacific.iessportal.persistent.Seal"

  table="tseal" dynamic-update="true" dynamic-insert="true"

  select-before-update="false" lazy="false">

  <id name="id" column="id" type="long">

   <generator class="increment"/>

  </id>

  <property name="sealName" type="string" column="sealName"

   not-null="false" unique="false" />

  <one-to-one name="sealData"

   class="com.indigopacific.iessportal.persistent.SealData"

   cascade="save-update" lazy="proxy">

  <set name="sealModels" cascade="save-update" lazy="true"

   outer-join="false" inverse="true">

   <key column="sealId" />

   <one-to-many

    class="com.indigopacific.iessportal.persistent.SealModel" />

  </set>

  <many-to-one name="branchInfo" column="branchInfoId"

   class="com.indigopacific.iessportal.persistent.BranchInfo"

   cascade="save-update" outer-join="false" lazy="false">

  </many-to-one>

</class>

</hibernate-mapping>

2、tsealData

<?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">

<hibernate-mapping>

<class name="com.indigopacific.iessportal.persistent.SealData"

  table="tsealdata" dynamic-update="true" dynamic-insert="true"

  select-before-update="false" lazy="true">

  <id name="id" column="id" type="long">

   <generator class="foreign">

    <param name="property">seal</param>

   </generator>

  </id>

  <one-to-one name="seal"

   class="com.indigopacific.iessportal.persistent.Seal" cascade="save-update"  constrained="true"/>

  <property name="sealString" type="string" column="sealString"

   not-null="false" unique="false" />

  

</class>

</hibernate-mapping>

如果我们保存tseal表时想同时保存tsealdata表数据，如果写成：

   Seal seal = new Seal();

   seal.setSealName("seal");

   SealData data = new SealData();

   data.setSealString("hello");

   seal.setSealData(data);

   session.save(seal);

会报如下异常：

org.hibernate.id.IdentifierGenerationException: attempted to assign id from null one-to-one property: seal

但是在oracle中不会这样，原因尚待分析。

需要改成如下解决问题：

   Seal seal = new Seal();

   seal.setSealName("seal");

   SealData data = new SealData();

   data.setSealString("hello");

   seal.setSealData(data);

   data.setSeal(seal);

   session.save(seal);

并发出如下sql语句：

Hibernate: insert into tseal (sealName, id) values (?, ?)

Hibernate: insert into tsealdata (sealString, id) values (?, ?)

原因是：

当我们保存tseal表时，由于没有提交，导致我们保存tsealdata时将null分配该表记录作为主键，因而报错。

 

这里如果将constrained="true"放到seal的hibernate mapping文件中保存时会报如下错误：

Caused by: java.sql.SQLException: Cannot add or update a child row: a foreign key constraint fails (`iess`.`tsealdata`, CONSTRAINT `FKDB17E37BF293309C` FOREIGN KEY (`id`) REFERENCES `tseal` (`id`))

 at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2926)

 at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1571)

 at com.mysql.jdbc.ServerPreparedStatement.serverExecute(ServerPreparedStatement.java:1120)

 at com.mysql.jdbc.ServerPreparedStatement.executeInternal(ServerPreparedStatement.java:675)

 at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1162)

 at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1079)

 at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1064)

 at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.executeUpdate(NewProxyPreparedStatement.java:105)

 at org.hibernate.jdbc.NonBatchingBatcher.addToBatch(NonBatchingBatcher.java:23)

 at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2197)

 ... 27 more