JPA OneToMany级联更新 及 orphanRemoval = true 说明

　

orphanremoval

下面是一个例子:
Employee ---- Address  (假设为单向one-to-many)
class Employee {
   @oneToMany(cascade = CascadeType.REMOVE, orphanRemoval = true)
   @JoinTable(JoinColumn="Employee_id")
   private Set<Address> addresses;
   // [当Employee和Address均处于关联时]这种场合设置cascade和orphanRemoval是一样的效果,只要设置一种就好
   // [当Employee和Address均不处于关联时,比如设置address中某条数据为空, 仅设置Cascade=Remove时,当操作到Employee只会将其对应的Address删掉
   // 设置orphanRemoval=true时,会将FK上Null对应的数据都会删掉(自动去孤子)
}
注意加入的位置
只能在one的一方设置orphanRemoval
cascade所有关系都可设置

oneToMany 使用：

示例：Employee与Phone为例.

1、类定义如下：

package com.vrvwh.wh01.domain;

import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;

/**
 * Created by Administrator on 2015/3/5.
 */
@Entity
public class Employee {
    private long id;

    private String name;

    private Set<Phone> phones=new HashSet<Phone>();

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    public long getId() {
        return id;
    }

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

    @Column
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
/**orphanRemoval=true配置表明删除无关联的数据。级联更新子结果集时此配置最关键
*/
    @OneToMany(mappedBy = "employee",cascade = CascadeType.ALL,orphanRemoval = true)
    public Set<Phone> getPhones() {
        return phones;
    }

    public void setPhones(Set<Phone> phones) {
        this.phones = phones;
    }
}

package com.vrvwh.wh01.domain;

import javax.persistence.*;

/**
 * Created by Administrator on 2015/3/5.
 */
@Entity(name="Phones")
public class Phone {
    @Id
    private int phoneId;
    private int phoneNumber;

    @ManyToOne(cascade= CascadeType.ALL)
    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;
    }

}

2、更新:

Employee employee=employeeService.query(1);
        employee.getPhones().clear();
        Phone phone1=new Phone();
        phone1.setPhoneNumber(132567);
        employee.getPhones().add(phone1);
        Phone phone2=new Phone();
        phone2.setPhoneNumber(132567);
        employee.getPhones().add(phone2);
        employeeService.update(employee);

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