我有 2 个表。一个叫Employee,一个叫Phones,一个员工可以有多个Phone。
员工类:
@Entity
@Table(name = "employee")
public class Employee {
@Id
@Column(name = "id", unique = true, nullable = false)
@GeneratedValue(strategy = javax.persistence.GenerationType.IDENTITY)
private Integer id;
@Column(name = "name", unique = true, nullable = false, length = 25)
private String name;
@OneToMany(mappedBy="owner", fetch= FetchType.EAGER, orphanRemoval=true, cascade={CascadeType.ALL})
private List<Phone> phones;
电话类:
@Entity
@Table(name = "phone")
public class Phone {
@Id
@Column(name = "id", unique = true, nullable = false)
@GeneratedValue(strategy = javax.persistence.GenerationType.IDENTITY)
private long id;
@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "employee_id")
private Employee owner;
@Column(name = "phone_type", nullable = false, length = 25)
private String phoneType;
@Column(name = "phone_number", nullable = false, length = 25)
private String phoneNumber;
假设我想为现有员工添加电话。我这样做:
Phone phone = new Phone();
phone.setOwner(employee);
phone.setPhoneNumber("999-555-0001");
phone.setPhoneType("home");
employee.getPhones().add(phone);
dao.merge(employee); // Is it possible to get this to both persist new phones and update existing phones that were changed?
鉴于 phoneSet 中的某些电话已经保留,我不确定如何合并新电话。我必须手动保留每部电话吗?一个例子将不胜感激。我研究了级联,但我似乎无法让它工作。我收到的错误是:java.lang.IllegalStateException:一个实体副本已分配给另一个实体。
最佳答案
我认为问题可能出在 Phone 类中的连接列注释中。您正在指定 employee_id
的连接列,但在 Employee 类中,id 字段的 @Column
注释映射到列 id
。
尝试更改/同步连接列:
@ManyToOne(fetch = FetchType.EAGER, targetEntity=your.package.here.Employee.class)
@JoinColumn(name = "id")
private Employee owner;
或
员工.java
@Id
@Column(name = "employee_id", unique = true, nullable = false)
@GeneratedValue(strategy = javax.persistence.GenerationType.IDENTITY)
private Integer id;
Phone.java
@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "employee_id", targetEntity=your.package.here.Employee.class)
private Employee owner;
关于java - JPA:如何使用 OneToMany 注释将新项目添加到列表中,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/13300386/