saveorupdate() 不更新休眠中的集合（列表）一对多映射

Question

班级 Student

public class Student {

private Long id;
private String name;
private String className;
private List<Phone> phones;
    // getter setter
 }

---

班级 Phone

public class Phone {

private Long id;
private String number;
   //getter setter
     }

-> 映射文件 Student.hbm.xml

     <id name="id" type="long" column="id">
        <generator class="native" />
    </id>

    <property name="name" column="name" type="string" />

    <property name="className" column="class_name" type="string" />

    <list name="phones" cascade="all-delete-orphan">
        <key column="student_id"/>
        <list-index column="idx" />
        <one-to-many class="Phone" />
    </list>

-> 映射文件 Phone.hbm.xml

    <id name="id" type="long" column="id">
        <generator class="native" />
    </id>

    <property name="number" column="number" type="string" />

当我尝试更新电话号码（列表）时，前一个条目没有被删除，但 idx（列表索引）和外键为空，新条目用正确的 idx 和外键标记！！其他数据（不是列表）完全更新。在这里，我从数据库中获取类对象，修改它并将对象传递给saveorupdate()，但没有帮助。试了这么久

读取和更新代码：

      private void readAndUpdateStudent() {
       Student student = null;
       Session session = HibernateUtil.getSessionFactory().openSession();
       String name = "John";
         try {

        String queryString = "from Student student where student.name =:name";
        Query query = session.createQuery(queryString);
        query.setString("name", name);
        student = (Student) query.uniqueResult();
        System.out.println(student.getName());
        student.setName("Mary");
        List<Phone> phones = new ArrayList<Phone>();
        phones.add(new Phone("555555")); //here if I SET rather adding, the already existing values, update is done accordingly 
        phones.add(new Phone("789789"));//but when I use the list as a string type(instead of Phone Type), adding a new 0bject deletes the previous 
        student.setPhones(phones);//entries and adds new list on its own  but not in the case of user defined type.

    } catch (Exception e) {     
        e.printStackTrace();
        if (session != null) {

            session.close();

        }

    }finally{

        session.close();
        updateStudent(student);
    }

}
private void updateStudent(Student student) {

    Session session = HibernateUtil.getSessionFactory().openSession();
    Transaction tx = null;

    try {
        tx = session.beginTransaction();
        session.saveOrUpdate(student);
        tx.commit();
    } catch (HibernateException e) {
        if (tx != null)
            tx.rollback();
        e.printStackTrace();
    } finally {
        session.close();
    }
}

Answer 1

如果您想更新手机列表，则不应该这样做

    List<Phone> phones = new ArrayList<Phone>();
    phones.add(new Phone("555555"));
    phones.add(new Phone("789789"));
    student.setPhones(phones);

上面的代码不会更新手机列表，而是创建一个全新的手机列表。要更新电话列表，您应该检索旧列表并更新其条目：

    List<Phone> phones = student.getPhones();
    phones.get(0).setNumber("666666");
    phones.get(1).setNumber("888888");
    session.saveOrUpdate(student);