Hibernate一对多问题

Question

我正在对一对多映射进行概念验证，但没有成功。我的架构如下：

Student ---->Phone

class Student

public class Student implements java.io.Serializable 
{
   private Set<Phone> studentPhoneNumbers = new HashSet<Phone>();
   // other setters and getters and constructors
}

class Phone

public class Phone implements java.io.Serializable 
{ 
  private Student student;
// other setters and getters and constructors
}

Student 映射文件：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated Dec 5, 2010 7:56:05 PM by Hibernate Tools 3.4.0.Beta1 -->
<hibernate-mapping>
    <class name="com.BiddingSystem.domain.Student" table="STUDENT">
        <id name="studentId" type="long">
            <column name="STUDENTID" />
            <generator class="native" />
        </id>
        <property name="studentName" type="java.lang.String">
            <column name="STUDENTNAME" />
        </property>
        <set name="studentPhoneNumbers" table="PHONE" inverse="true" cascade="all">
            <key>
                <column name="STUDENTID" not-null="true" />
            </key>
            <one-to-many class="com.BiddingSystem.domain.Phone" />
        </set>
    </class>
</hibernate-mapping>

电话映射文件：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated Dec 5, 2010 7:56:05 PM by Hibernate Tools 3.4.0.Beta1 -->
<hibernate-mapping>
    <class name="com.BiddingSystem.domain.Phone" table="PHONE">
        <id name="phoneId" type="long">
            <column name="PHONEID" />
            <generator class="native" />
        </id>
        <property name="phoneType" type="java.lang.String">
            <column name="PHONETYPE" />
        </property>
        <property name="phoneNumber" type="java.lang.String">
            <column name="PHONENUMBER" />
        </property>
        <many-to-one name="student" class="com.BiddingSystem.domain.Student" not-null="true">
            <column name="STUDENTID" not-null="true"/>
        </many-to-one>
    </class>
</hibernate-mapping>

但是当我这样做时：

            Session session = gileadHibernateUtil.getSessionFactory().openSession();
        Transaction transaction = session.beginTransaction();

        Set<Phone> phoneNumbers = new HashSet<Phone>();
        phoneNumbers.add(new Phone("house","32354353"));
        phoneNumbers.add(new Phone("mobile","9889343423"));

        Student student = new Student("Eswar", phoneNumbers);
        session.save(student);

        transaction.commit();
        session.close();

我收到以下错误：

    Caused by: org.hibernate.PropertyValueException: not-null property references a null or transient value: com.BiddingSystem.domain.Phone.student
        at org.hibernate.engine.Nullability.checkNullability(Nullability.java:101)
        at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:313)
        at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:204)
        at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:144)


    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)
        at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)
        at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:117)
        at 

org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
    at org.hibernate.impl.SessionImpl.fireSaveOrUpdate(SessionImpl.java:677)
    at org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:669)
    at org.hibernate.engine.CascadingAction$5.cascade(CascadingAction.java:252)
    at org.hibernate.engine.Cascade.cascadeToOne(Cascade.java:392)
    at org.hibernate.engine.Cascade.cascadeAssociation(Cascade.java:335)
    at org.hibernate.engine.Cascade.cascadeProperty(Cascade.java:204)
    at org.hibernate.engine.Cascade.cascadeCollectionElements(Cascade.java:425)
    at org.hibernate.engine.Cascade.cascadeCollection(Cascade.java:362)
    at org.hibernate.engine.Cascade.cascadeAssociation(Cascade.java:338)
    at org.hibernate.engine.Cascade.cascadeProperty(Cascade.java:204)
    at org.hibernate.engine.Cascade.cascade(Cascade.java:161)
    at org.hibernate.event.def.AbstractSaveEventListener.cascadeAfterSave(AbstractSaveEventListener.java:476)
    at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:354)
    at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:204)
    at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:144)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)
    at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)
    at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
    at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:705)
    at org.hibernate.impl.SessionImpl.save(SessionImpl.java:693)
    at org.hibernate.impl.SessionImpl.save(SessionImpl.java:689)
    at com.BiddingSystem.server.GreetingServiceImpl.greetServer(GreetingServiceImpl.java:52)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at net.sf.gilead.gwt.PersistentRemoteService.processCall(PersistentRemoteService.java:174)
    ... 21 more

有人可以帮助为此设置正确的属性吗 电话映射 xml 文件

<many-to-one name="student" class="com.BiddingSystem.domain.Student" not-null="true">
            <column name="STUDENTID" not-null="true"/>
</many-to-one>

和学生映射文件

<set name="studentPhoneNumbers" table="PHONE" inverse="true" cascade="all">
            <key>
                <column name="STUDENTID" not-null="true" />
            </key>
            <one-to-many class="com.BiddingSystem.domain.Phone" />
</set>

Answer 1

您需要将 Student 对象推入 Phone 对象：

foreach (Phone phone : student.getStudentPhoneNumbers()) {
    phone.setStudent(student);
}

更典型的代码片段将首先创建 Student 实例，然后向其中添加电话号码。我经常实现一个方法来帮助解决这个问题，例如在 Student.java 中：

public void addPhoneNumber(Phone phone) {
    phone.setStudent(this);
    getStudentPhoneNumbers().add(phone);
}
public void addPhoneNumber(String type, String number) {
    addPhoneNumber(new Phone(type, number));
}

所以现在你可以说 student.addPhoneNumber("home", "12354") 它会简单地执行 DTRT。

Answer 2

由于您使用带有 inverse=true 选项的双向关联，因此子对象将独立保留。父对象不关心与子对象的同步。因此，在这种情况下，将有一个针对父对象的插入查询和与子对象一样多的插入查询。因此，子对象在插入时需要具有父对象的引用。此外，您还在父级和子级定义了 not-null=true 。

当我们使用 inverse=false 时，将首先保存父对象，然后在不引用父对象的情况下保存子对象，最后父对象将使用更新查询更新其与子对象的关系。

希望这有帮助。

Answer 3

1).电话号码必须有学生，因此首先创建一个学生对象 (stu = new Student()) 并
然后调用phone.setStudent(stu);

前任：

   Set<Phone> phoneNumbers = new HashSet<Phone>();

   Phone p1 = new Phone("house", "32354353");

   phoneNumbers.add(p1);
   Phone p2 = new Phone("mobile", "9889343423");
   phoneNumbers.add(p2);

   Student student = new Student("Eswar", phoneNumbers);
   student.setPhones(phoneNumbers);
   session.save(student); //Till now, This code is work if you use cascade = 'all' in            //my_mapping_file.xml or

   session.save(p1); session.save(p2); //call session.save on both phone objects