[英]How can i establish a one to one relationship between this two classes using spring boot jpa?, also, how do i save the entities?
[英]Using Spring Boot, how can I create the relationship between 2 entities on a new table and give it extra columns?
我有这两个实体:
@Data
@Entity
@AllArgsConstructor
@NoArgsConstructor
@Table(name = "Workplace")
public class Employee {
@Id
@GeneratedValue
int id;
String name;
String dni;
java.time.LocalDate startDate;
}
@Data
@Entity
@AllArgsConstructor
@NoArgsConstructor
@Table(name = "Workplace")
public class Workplace {
@Id
@GeneratedValue
int id;
String code;
String location;
}
一个工作区可以有许多员工。 我需要将关系存储在一个新表中(我们称之为Contract
),并且我需要它具有以下字段:
int idEmployee;
int idWorkplace;
java.time.LocalDate startDate;
java.time.LocalDate endDate;
startDate
字段必须从 Employee 中获取,但endDate
默认为空。
我怎样才能做到这一点?
您需要手动创建它
@IdClass(ContractId.class)
@Data
@Entity
@AllArgsConstructor
@NoArgsConstructor
@Table(name = "Contract")
public class Contract {
@Id
private int idEmployee;
@Id
private int idWorkplace;
private java.time.LocalDate startDate;
private java.time.LocalDate endDate;
@OneToOne
Employee employee
}
然后你还需要那个复合键
@Data
@AllArgsConstructor
@NoArgsConstructor
public class ContractId implements Serializable {
private int idEmployee;
private int idWorkplace;
}
然后你的相关类需要对这些关系进行一些额外的修改
@Data
@Entity
@AllArgsConstructor
@NoArgsConstructor
@Table(name = "Workplace")
public class Workplace {
@Id
@GeneratedValue
int id;
String code;
String location;
@OneToMany(mappedBy = "idWorkplace")
private List<Contract> contracts;
}
@Data
@Entity
@AllArgsConstructor
@NoArgsConstructor
@Table(name = "Workplace")
public class Employee {
@Id
@GeneratedValue
int id;
String name;
String dni;
java.time.LocalDate startDate;
@OneToOne(mappedBy = "idEmployee")
Contract contract
}
然后根据您的要求
startDate 字段必须从 Employee 中获取,但 endDate 默认为空。
您可以在保留这些合同实体时手动处理它
或者
将其从 Employee 中完全删除,并仅在 Contract 中。 这对我来说是最佳实践。
我找到了这样做的方法:
@Getter
@Setter
@Entity
@AllArgsConstructor
@NoArgsConstructor
public class MyOtherTable {
@Id
@GeneratedValue
private Integer id;
@OneToOne
private Workplace workplace;
@OneToOne
private Employee employee;
private String otherProperty;
}
@Data
@Entity
@AllArgsConstructor
@NoArgsConstructor
@Table(name = "Employee")
public class Employee {
@Id
@GeneratedValue
private int id;
private String name;
private String dni;
private java.time.LocalDate startDate;
@OneToOne
private WorkPlace workplace;
}
我不确定您为什么要为一对多关系创建一个新表。 通常我们只在存在多对多关系的情况下创建新表。 当我们有多对多关系时,我们创建了具有复合主键的第三个关系表。 为什么需要为一对多创建第三个关系表。
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