Hibernate 一对多关系不为外键提供值

Question

我已经有一段时间没有使用 Hibernate 了，前几天我想做一些简单的例子，但是当我需要做一个一对多的关系时，多边没有被插入到数据库中。这是数据库的样子。

这是我给这个人的映射：

Java

public class ORMPerson implements Serializable {

private Long uniqueId;
private String firstName;
private String secondName;
private Long fkAddress;

hbm

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


<hibernate-mapping package="orm">
    <class name="orm.ORMPerson" table="PERSON">
        <id name="uniqueId" column="UNIQUE_ID">
            <generator class="increment"/>
        </id>

        <property name="firstName" column="FIRST_NAME"/>
        <property name="secondName" column="SECOND_NAME"/>

        <many-to-one name="fkAddress" class="orm.ORMPerson" column="FK_ADDRESS" cascade="all" not-null="false" />
    </class>
</hibernate-mapping>

这是地址的映射：

Java

public class ORMAddress implements Serializable {

private Long uniqueId;
private String firstLine;
private String secondLine;
private String postcode;
private Set<ORMPerson> ormPersons;

hbm

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


<hibernate-mapping package="orm">
    <class name="orm.ORMAddress" table="ADDRESS">
        <id name="uniqueId" column="UNIQUE_ID">
            <generator class="increment"/>
        </id>

        <property name="firstLine" column="FIRST_LINE"/>
        <property name="secondLine" column="SECOND_LINE"/>
        <property name="postcode" column="POSTCODE"/>


        <set name="ormPersons" table="ADDRESS" inverse="true" fetch="select" cascade="save-update">
            <key>
                <column name="UNIQUE_ID" not-null="true" />
            </key>
            <one-to-many class="ORMPerson"/>
        </set>

    </class>
</hibernate-mapping>

这是我用来插入多人地址的客户端代码：

ORMAddress ormAddress = new ORMAddress();
        ormAddress.setFirstLine(address.getFirstLine());
        ormAddress.setSecondLine(address.getSecondLine());
        ormAddress.setPostcode(address.getPostcode());
        ormAddress.setOrmPersons(ormPersons);


        session.save(ormAddress);

        session.getTransaction().commit();

如果我尝试用 ormPersons 调用 session.save() 方法，我会看到数据被添加到数据库中，但外来 kew 将没有任何价值。我认为这是因为我在 Person 中只有一个 not-null="false" 但这不是解决方案，我认为只需调用一次保存方法就可以自动插入所有内容。

Answer 1

原因隐藏在inverse="true"映射中。这是对 Hibernate 说：

when you persist collection - let that job on its items. These items must be aware of their parent.

但是正如我们在上面看到的，ormPersons 没有提供对 ormAddress 的反向引用。

...
// after that line we have to do more
ormAddress.setOrmPersons(ormPersons);
// we have to assign back reference
for(ORMPerson ormPerson: ormPersons)  {
    ormPerson.setOrmAddress(ormAddress);
}

而且我们还需要 ORMPerson 内部的 ORMAddress 引用 - 而不是 LONG

public class ORMPerson implements Serializable {
...
private ORMAddress ormAddress;

hbm

<class name="orm.ORMPerson" table="PERSON">
    ....
    <many-to-one name="ormAddress" class="orm.ORMPerson" 
        column="FK_ADDRESS" cascade="all" not-null="false" />
</class>

最后，多对一和一对多必须使用相同的列

hbm 地址 (FK_ADDRESS):

<class name="orm.ORMAddress" table="ADDRESS">
    ...
    <set name="ormPersons" table="ADDRESS" inverse="true" 
         fetch="select" cascade="save-update">
        <key>
            //<column name="UNIQUE_ID" not-null="true" />
            <column name="FK_ADDRESS" not-null="true" /> // the parent id
        </key>
        <one-to-many class="ORMPerson"/>
    </set>

查看文档以获取示例：

23.2. Bidirectional one-to-many

Hibernate 一对多关系不为外键提供值

Hibernate one to many relationship does not provide value for foreign key

java

database

orm

hibernate