[英]How to copy primary key from master table to child table in Hibernate
如何在Hibernate中將主鍵(共享鍵)從主表復制到子表。 我正在嘗試進行單向映射( Employee
引用了Address
,反之亦然)。
附加信息:Hibernate依賴項:
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>5.4.1.Final</version>
</dependency>
我有如下所示的Employee
類和Address
實體。 我正在嘗試在Employee
實體到Address
實體中生成主鍵。
但是,我看到ADDRESS
表中的employeeId
始終由休眠生成為0(我希望將其復制)。 我想我在使用@PrimaryKeyJoinColumn
或@MapsId
。 我嘗試將兩者都添加,或在其中添加一個,但沒有運氣。
以下是該架構的對應表:
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)
);
實體映射如下所示:
Employee.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 +
'}';
}
}
Address.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;
}
您需要在復制主鍵值的實體上對關聯進行建模。 如果這樣做,則可以使用@MapsId
注釋關聯。
在您的示例中,使用IDENTITY策略生成Employee
實體的主鍵,並且Address
實體應使用相同的值。 為此,您需要在Address
實體上建立一對一關聯的模型。 您可以使用雙向或單向關聯映射。
如果您喜歡單向的,則可以使用與Employee
實體的address
屬性相同的映射注釋。 然后,您當然需要隨后刪除address
屬性;)
在雙向映射中,您的Employee
實體如下所示:
@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 +
'}';
}
}
這是Address
實體。 此映射的重要部分是一對一關聯上的@MapsId
批注。
@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 + '\'' +
'}';
}
}
如您所見,我刪除了@PrimaryKeyJoinColumn
批注。 僅當您的實體映射到2個數據庫表時使用。 如果您使用繼承策略JOINED或使用舊數據庫並需要將2個表映射到同一實體,則可能是這種情況。
我認為您不需要手動復制主鍵。 如果您使用的是像休眠這樣的ORM,則實際上需要將實體對象(在您的情況下為Address實體對象)傳遞給要為其創建1-1映射的類對象(在您的情況下為Employee)。 Hibernate將自動使用實體主鍵(地址主鍵)填充映射實體中的列(Employee表中的address列)。 您可以在此處查看與您的案例非常相似的示例: https : //dzone.com/tutorials/java/hibernate/hibernate-example/hibernate-mapping-one-to-one-using-annotations-1.html
如果您看到的話,它們在地址表中有一個主鍵,即addressId。 現在在學生班級中,他們有一個地址類型的字段,該字段被標記為@OneToOne,表示其映射。 現在,在學生類構造函數中,我們正在傳遞地址對象。 現在,在主函數中,如果您看到的是,我們僅保存了學生對象(而不是地址對象)。 現在,當保存交易時,休眠將知道,首先創建地址實體,因為學生實體依賴該地址實體,然后使用創建的地址實體的主鍵保存學生實體。
現在,當您獲取學生實體時,hibernate還將在查看學生表中的addressId的同時自動獲取地址實體。 希望能幫助到你。 讓我知道是否需要進一步澄清。
我已將實體映射如下:
在Employee.java
中的代碼中查看以下內容
@OneToOne(fetch = FetchType.LAZY)
@PrimaryKeyJoinColumn
private Address address;
Employee.java
@Entity
@Table(name = "EMPLOYEE")
public class Employee implements Serializable {
public Employee(){
}
public Employee(String name){
this.name = name;
}
public Employee(String name,double salary){
this.name = name;
this.salary = salary;
}
@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(fetch = FetchType.LAZY)
@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 "BiEmployee{" +
"id=" + id +
", name='" + name + '\'' +
", salary=" + salary +
", address=" + address +
'}';
}
}
Address.java
@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(fetch = FetchType.LAZY)
@JoinColumn(name = "COUNTRY_CODE")
private Country country;
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 Country getCountry() {
return country;
}
public Address setCountry(Country country) {
this.country = country;
return this;
}
@Override
public String toString() {
return "BiAddress{" +
"id=" + id +
", streetName='" + streetName + '\'' +
", cityName='" + cityName + '\'' +
", stateName='" + stateName + '\'' +
", zipCode='" + zipCode + '\'' +
'}';
}
}
添加Country.java以獲得完整性
@Entity
@Table(name = "COUNTRY")
public class Country {
@Id
@Column(name = "COUNTRY_CODE")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int countryCode;
@Column(name = "COUNTRY_NAME")
private String name;
public int getCountryCode() {
return countryCode;
}
public Country setCountryCode(int countryCode) {
this.countryCode = countryCode;
return this;
}
public String getName() {
return name;
}
public Country setName(String name) {
this.name = name;
return this;
}
}
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.