如何在 Hibernate 中将主键(共享键)从主表复制到子表。我正在尝试进行单向映射(Employee
引用了Address
,反之亦然)。
附加信息: hibernate 依赖:
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>5.4.1.Final</version>
</dependency>
我有 Employee
类和 Address
实体,如下所示。我正在尝试在 Employee
实体中生成主键到 Address
实体。
但是,我看到 ADDRESS
表中的 employeeId
始终由 hibernate 生成为 0(我希望复制它)。我想我在使用 @PrimaryKeyJoinColumn
或 @MapsId
时会做错。我尝试过添加两者,或者添加其中之一,但没有成功。
以下是对应表的架构:
create table EMPLOYEE(
EMPLOYEE_ID int auto_increment,
NAME varchar(100),
SALARY double,
primary key(EMPLOYEE_ID)
);
create table ADDRESS
(
EMPLOYEE_ID int references EMPLOYEE.EMPLOYEE_ID,
STREET_NAME varchar(40),
CITY_NAME varchar(40),
STATE_NAME varchar(40),
ZIP_CODE varchar(40),
primary key(EMPLOYEE_ID)
);
实体映射如下所示:
员工.java
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.MapsId;
import javax.persistence.OneToOne;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.Table;
import java.io.Serializable;
@Entity
@Table(name = "EMPLOYEE")
public class Employee implements Serializable {
@Id
@Column(name = "EMPLOYEE_ID")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
@Column(name = "NAME")
private String name;
@Column(name = "SALARY")
private double salary;
@OneToOne
@JoinColumn(name="EMPLOYEE_ID")
@MapsId
//@PrimaryKeyJoinColumn
private Address address;
public int getId() {
return id;
}
public Employee setId(int id) {
this.id = id;
return this;
}
public String getName() {
return name;
}
public Employee setName(String name) {
this.name = name;
return this;
}
public double getSalary() {
return salary;
}
public Employee setSalary(double salary) {
this.salary = salary;
return this;
}
public Address getAddress() {
return address;
}
public Employee setAddress(Address address) {
this.address = address;
return this;
}
@Override
public String toString() {
return "Employee{" +
"id=" + id +
", name='" + name + '\'' +
", salary=" + salary +
", address=" + address +
'}';
}
}
地址.java
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.MapsId;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.Table;
import java.io.Serializable;
@Entity
@Table(name = "ADDRESS")
public class Address implements Serializable {
@Id
@Column(name = "EMPLOYEE_ID")
private int id;
@Column(name = "STREET_NAME")
private String streetName;
@Column(name = "CITY_NAME")
private String cityName;
@Column(name = "STATE_NAME")
private String stateName;
@Column(name = "ZIP_CODE")
private String zipCode;
public int getId() {
return id;
}
public Address setId(int id) {
this.id = id;
return this;
}
public String getStreetName() {
return streetName;
}
public Address setStreetName(String streetName) {
this.streetName = streetName;
return this;
}
public String getCityName() {
return cityName;
}
public Address setCityName(String cityName) {
this.cityName = cityName;
return this;
}
public String getStateName() {
return stateName;
}
public Address setStateName(String stateName) {
this.stateName = stateName;
return this;
}
public String getZipCode() {
return zipCode;
}
public Address setZipCode(String zipCode) {
this.zipCode = zipCode;
return this;
}
@Override
public String toString() {
return "Address{" +
"id=" + id +
", streetName='" + streetName + '\'' +
", cityName='" + cityName + '\'' +
", stateName='" + stateName + '\'' +
", zipCode='" + zipCode + '\'' +
'}';
}
}
保存方法:
public Employee save(Employee employee){
Session session = HibernateUtil.buildSessionFactory().openSession();
Transaction transaction = session.beginTransaction();
session.save(address); // Should I do this?
session.save(employee);
transaction.commit();
return employee;
}
最佳答案
您需要在复制主键值的实体上对关联进行建模。如果这样做,您可以使用 @MapsId
注释关联。
在您的示例中,Employee
实体的主键是使用 IDENTITY strategy 生成的。 ,并且 Address
实体应使用相同的值。为了实现这一点,您需要对 one-to-one association 进行建模在 Address
实体上。您可以使用双向或单向关联映射。
如果您更喜欢单向注释,则可以使用与 Employee
实体的 address
属性相同的映射注释。当然,之后您需要删除 address
属性;)
在双向映射中,您的 Employee
实体将如下所示:
@Entity
@Table(name = "EMPLOYEE")
public class Employee implements Serializable {
@Id
@Column(name = "EMPLOYEE_ID")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
@Column(name = "NAME")
private String name;
@Column(name = "SALARY")
private double salary;
@OneToOne
@JoinColumn(name="EMPLOYEE_ID")
private Address address;
public int getId() {
return id;
}
public Employee setId(int id) {
this.id = id;
return this;
}
public String getName() {
return name;
}
public Employee setName(String name) {
this.name = name;
return this;
}
public double getSalary() {
return salary;
}
public Employee setSalary(double salary) {
this.salary = salary;
return this;
}
public Address getAddress() {
return address;
}
public Employee setAddress(Address address) {
this.address = address;
return this;
}
@Override
public String toString() {
return "Employee{" +
"id=" + id +
", name='" + name + '\'' +
", salary=" + salary +
", address=" + address +
'}';
}
}
这是Address
实体。此映射的重要部分是一对一关联上的 @MapsId
注释。
@Entity
@Table(name = "ADDRESS")
public class Address implements Serializable {
@Id
@Column(name = "EMPLOYEE_ID")
private int id;
@Column(name = "STREET_NAME")
private String streetName;
@Column(name = "CITY_NAME")
private String cityName;
@Column(name = "STATE_NAME")
private String stateName;
@Column(name = "ZIP_CODE")
private String zipCode;
@OneToOne(mappedBy="address")
@MapsId
private Employee employee
public int getId() {
return id;
}
public Address setId(int id) {
this.id = id;
return this;
}
public String getStreetName() {
return streetName;
}
public Address setStreetName(String streetName) {
this.streetName = streetName;
return this;
}
public String getCityName() {
return cityName;
}
public Address setCityName(String cityName) {
this.cityName = cityName;
return this;
}
public String getStateName() {
return stateName;
}
public Address setStateName(String stateName) {
this.stateName = stateName;
return this;
}
public String getZipCode() {
return zipCode;
}
public Address setZipCode(String zipCode) {
this.zipCode = zipCode;
return this;
}
public Employee getEmployee() {
return employee;
}
public void setEmployee(Employee emp) {
this.employee = emp;
}
@Override
public String toString() {
return "Address{" +
"id=" + id +
", streetName='" + streetName + '\'' +
", cityName='" + cityName + '\'' +
", stateName='" + stateName + '\'' +
", zipCode='" + zipCode + '\'' +
'}';
}
}
如您所见,我删除了 @PrimaryKeyJoinColumn
注释。仅当您的实体映射到 2 个数据库表时才使用它。如果您使用inheritance strategy JOINED,可能会出现这种情况或者如果您使用旧数据库并需要 map 2 tables to the same entity .
关于java - 如何在Hibernate中将主键从主表复制到子表,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/54455718/