jpa一对多

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aoerqilengbai 2021-09-08 09:14:22 ©著作权

文章标签 jpa一对多 java mysql 一对多数据库 文章分类 Java 后端开发

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package com.demo.beans;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;

@Entity(name="Phones")
public class Phone {
@Id
private int phoneId;
private int phoneNumber;

@ManyToOne(cascade=CascadeType.ALL)
@JoinColumn(name="employeeId")
private Employee employee;

public int getPhoneId() {
return phoneId;
}
public void setPhoneId(int phoneId) {
this.phoneId = phoneId;
}
public int getPhoneNumber() {
return phoneNumber;
}
public void setPhoneNumber(int phoneNumber) {
this.phoneNumber = phoneNumber;
}
public Employee getEmployee() {
return employee;
}
public void setEmployee(Employee employee) {
this.employee = employee;
}

}

package com.demo.beans;

import java.util.Collection;
import java.util.List;
import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.ElementCollection;
import javax.persistence.Entity;
import javax.persistence.EntityListeners;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.OneToOne;

@Entity
@EntityListeners(MyMonitor.class)
public class Employee {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private int id;

private String employeeName;

@ElementCollection(targetClass = EmployeePeriod.class)
private Collection employeePeriod;
@ElementCollection
private Set<String> nickName;

@OneToMany(mappedBy="employee", cascade=CascadeType.ALL)
private List<Phone> phones;

@OneToOne(cascade=CascadeType.ALL)
@JoinColumn(name="AddressId")
private Address address;

public Address getAddress() {
return address;
}

public void setAddress(Address address) {
this.address = address;
}

public Collection getEmployeePeriod() {
return employeePeriod;
}

public void setEmployeePeriod(Collection employeePeriod) {
this.employeePeriod = employeePeriod;
}

public Set<String> getNickName() {
return nickName;
}

public void setNickName(Set<String> nickName) {
this.nickName = nickName;
}

public String getEmployeeName() {
return employeeName;
}

public int getId() {
return id;
}

public void setId(int id) {
this.id = id;
}

public void setEmployeeName(String employeeName) {
this.employeeName = employeeName;
}

public List getPhones() {
return phones;
}

public void setPhones(List phones) {
this.phones = phones;
}

}

Employee employee = new Employee();


employee.setEmployeeName("John Bai");
Phone phone = new Phone();
phone.setPhoneId(1);

phone.setPhoneNumber(123);


Phone phone2 = new Phone();
phone2.setPhoneId(2);

phone2.setPhoneNumber(123);

phone2.setEmployee(employee);
List<Phone> l = new LinkedList<Phone>();
l.add(phone);
l.add(phone2);
employee.setPhones(l);
userRepository.addEmployee(employee);

注意到第一个手机对象没有设置employee，结果后台数据库中表的记录如下：

mysql> select * from phones;
+---------+-------------+------------+
| phoneId | phoneNumber | employeeId |
+---------+-------------+------------+
| 1 | 123 | NULL |
| 2 | 123 | 5 |
+---------+-------------+------------+
2 rows in set (0.00 sec)

mysql> select * from employee;
+----+--------------+-----------+
| id | employeeName | AddressId |
+----+--------------+-----------+
| 1 | John Smith | 1 |
| 2 | John Bai | NULL |
| 5 | John Bai | NULL |
+----+--------------+-----------+