休眠一对一映射问题 [英] Hibernate one to one mapping problem

问题描述

我正在尝试在休眠模式下进行一对一映射，hbm文件和类如下，

I'm trying one-to-one mapping in hibernate, The hbm files and the classes are as follows,

Student.hbm.xml:

Student.hbm.xml :

<hibernate-mapping>
    <class name="com.psl.student.Student" table="STUDENT">
        <meta attribute="class-description">This class contains student details.</meta>
        <id name="studentId" type="long" column="STUDENT_ID">
            <generator class="native" />
        </id>
        <property name="studentName" type="string" length="100"  column="STUDENT_NAME" />
        <one-to-one name="studentAddress" class="com.psl.student.Address" not-null="true" column ="STUDENT_ADDRESS"  />
    </class>
</hibernate-mapping>

Address.hbm.xml:

Address.hbm.xml :

<hibernate-mapping>
    <class name="com.psl.student.Address" table="ADDRESS">

    <meta attribute="class-description">This class contains the student's address details.</meta>
    <id name="addressId" type="long" column="ADDRESS_ID">
        <generator class="native" />
    </id>

    <property name="street" column="ADDRESS_STREET" type="string" length="250" />
    <property name="city" column="ADDRESS_CITY" type="string" length="50" />
    <property name="state" column="ADDRESS_STATE" type="string" length="50" />
    <property name="zipcode" column="ADDRESS_ZIPCODE" type="string" length="10" />
</class>

</hibernate-mapping>

Student.java:

Student.java:

public class Student implements java.io.Serializable {
private long studentId;
private String studentName;
private Address studentAddress;     

public Student() {
}

public Student(String studentName, Address studentAddress) {
    this.studentName = studentName;
    this.studentAddress = studentAddress;
}

public long getStudentId() {
    return this.studentId;
}

public void setStudentId(long studentId) {
    this.studentId = studentId;
}

public String getStudentName() {
    return this.studentName;
}

public void setStudentName(String studentName) {
    this.studentName = studentName;
}

public Address getStudentAddress() {
    return this.studentAddress;
}

public void setStudentAddress(Address studentAddress) {
    this.studentAddress = studentAddress;
}
}

Address.java:

Address.java :

public class Address implements java.io.Serializable {

private long addressId;
private String street;
private String city;
private String state;
private String zipcode;

public Address() {
}

public Address(String street, String city, String state, String zipcode) {
    this.street = street;
    this.city = city;
    this.state = state;
    this.zipcode = zipcode;
}

public long getAddressId() {
    return this.addressId;
}

public void setAddressId(long addressId) {
    this.addressId = addressId;
}

public String getStreet() {
    return this.street;
}

public void setStreet(String street) {
    this.street = street;
}

public String getCity() {
    return this.city;
}

public void setCity(String city) {
    this.city = city;
}

public String getState() {
    return this.state;
}

public void setState(String state) {
    this.state = state;
}

public String getZipcode() {
    return this.zipcode;
}

public void setZipcode(String zipcode) {
    this.zipcode = zipcode;
}
}

我收到关注错误:

原因:org.hibernate.InvalidMappingException:无法从资源com/psl/student/Student.hbm.xml解析映射文档

Caused by: org.hibernate.InvalidMappingException: Could not parse mapping document from resource com/psl/student/Student.hbm.xml

由以下原因引起:org.xml.sax.SAXParseException:必须为元素类型一对一"声明属性"not-null".

Caused by: org.xml.sax.SAXParseException: Attribute "not-null" must be declared for element type "one-to-one".

推荐答案

您不能同时在两个表上同时使用一对一和id生成器.

You can't use one-to-one and a id-generator on both tables at the same time.

表示主键已同步.在这种情况下:一个人和一个具有相同ID的地址将属于同一个人.因为学生引用了地址，所以学生的主键将充当外键来寻址，并且需要使用地址的主键.当它使用本地生成器生成自己的ID时，这是不可能的.

one-to-one in a relational database means that the primary keys get synchronized. In this case: a person and an address with the same id will belong together. Because the student references the address, the students primary key would act as a foreign key to address and need to use the addresses primary key. This isn't possible when it generates its own id using the native generator.

大多数一对一的关系实际上不应该是一对一的.如果您只想在该地址上使用外键，则只需将其映射为多对一即可.

Most one-to-one relations shouldn't actually be one-to-one. If you just want to have a foreign key to the address, map it simply as many-to-one.

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