Hibernate TransientPropertyValueException 在保存数据时

Question

我正在尝试使用 hibernate 将数据插入数据库。以下是我将如何执行该操作

    session.beginTransaction();
    pojo.StuDetails stu = new StuDetails();
    stu.setFName(f_name);
    stu.setLName(l_name);
    stu.setSex(sex);
    stu.setDob(dob);

    pojo.Subject sub = new Subject(subject, day, time);
    pojo.SubjectHasStuDetails shs = new SubjectHasStuDetails(stu, sub);

    session.save(shs);
    session.getTransaction().commit();

但是它给我一个错误说

Exception in thread "main" org.hibernate.TransientPropertyValueException: Not-null property references a transient value - transient instance must be saved before current operation

这是我的学生详细信息实体

 public class StuDetails  implements java.io.Serializable {


 private Integer id;
 private String FName;
 private String LName;
 private String sex;
 private String dob;
 private Set subjectHasStuDetailses = new HashSet();
 ...
 //constructors and getters, setters

我的学生详情hbm.xml

<hibernate-mapping>
    <class name="pojo.StuDetails" table="stu_details" catalog="laravel_test" optimistic-lock="version">
        <id name="id" type="java.lang.Integer">
            <column name="id" />
            <generator class="identity" />
        </id>
        <property name="FName" type="string">
            <column name="f_name" length="45" not-null="true" />
        </property>
        <property name="LName" type="string">
            <column name="l_name" length="45" not-null="true" />
        </property>
        <property name="sex" type="string">
            <column name="sex" length="45" not-null="true" />
        </property>
        <property name="dob" type="string">
            <column name="dob" length="45" not-null="true" />
        </property>
        <set name="subjectHasStuDetailses" table="subject_has_stu_details" inverse="true" lazy="true" fetch="select">
            <key>
                <column name="stu_details_id" not-null="true" />
            </key>
            <one-to-many class="pojo.SubjectHasStuDetails" />
        </set>
    </class>
</hibernate-mapping>

我的主题实体看起来像

 public class Subject  implements java.io.Serializable {


 private Integer id;
 private String subName;
 private String day;
 private String time;
 private Set subjectHasStuDetailses = new HashSet();

 ...
 //constructors and getters, setters

主题。hbm.xml

<hibernate-mapping>
    <class name="pojo.Subject" table="subject" catalog="laravel_test" optimistic-lock="version">
        <id name="id" type="java.lang.Integer">
            <column name="id" />
            <generator class="identity" />
        </id>
        <property name="subName" type="string">
            <column name="sub_name" length="45" not-null="true" />
        </property>
        <property name="day" type="string">
            <column name="day" length="45" not-null="true" />
        </property>
        <property name="time" type="string">
            <column name="time" length="45" not-null="true" />
        </property>
        <set name="subjectHasStuDetailses" table="subject_has_stu_details" inverse="true" lazy="true" fetch="select">
            <key>
                <column name="subject_id" not-null="true" />
            </key>
            <one-to-many class="pojo.SubjectHasStuDetails" />
        </set>

    </class>
</hibernate-mapping>

这是 SubjetcHasStuDetails 实体

 public class SubjectHasStuDetails  implements java.io.Serializable {


 private Integer id;
 private StuDetails stuDetails;
 private Subject subject;
 ...
 //constructors and getters, setters

SubjectHasStuDetials.hbm.xml

<hibernate-mapping>
    <class name="pojo.SubjectHasStuDetails" table="subject_has_stu_details" 
           catalog="laravel_test" optimistic-lock="version">
        <id name="id" type="java.lang.Integer">
            <column name="id" />
            <generator class="identity" />
        </id>
        <many-to-one name="stuDetails" class="pojo.StuDetails" fetch="select">
            <column name="stu_details_id" not-null="true" />
        </many-to-one>
        <many-to-one name="subject" class="pojo.Subject" fetch="select" >
            <column name="subject_id" not-null="true" />
        </many-to-one>
    </class>
</hibernate-mapping>

有人可以帮我解决这个错误吗...谢谢..

Answer 1

在您的SubjectHasStuDetials.hbm.xml中进行这些更改：

<many-to-one name="stuDetails" class="pojo.StuDetails" fetch="select" cascade="all">
            <column name="stu_details_id" not-null="true" />
        </many-to-one>
<many-to-one name="subject" class="pojo.Subject" fetch="select" cascade="all" >
            <column name="subject_id" not-null="true" />
        </many-to-one>

将 cascade="all" 属性添加到 stuDetails 和 subject 多对一标签。

Cascade 属性 是必需的，每当我们应用关系时在对象之间，级联属性传输在一个对象上完成的操作对象到其相关的子对象上
如果我们写 cascade = “all” 那么父 class 对象的变化将会如果我们写 cascade = “all”，也会对子 class 对象产生影响那么父对象的所有操作，如插入、删除、更新都将也影响子对象。
示例：如果我们对父级应用插入（或更新或删除）操作 class 对象，那么子 class 对象也将存储到数据库。

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