Question

我用：

SpringBoot 1.5.1
MariaDB / MySQL 10.1.14 / 15.1
org.hibernate.dialect.MySQL5Dialect
Hibernate5（SpringBoot默认）

这是SQL-Table-Definition：

CREATE TABLE salaries (
emp_no      BIGINT          NOT NULL,
salary      BIGINT          NOT NULL,
from_date   DATETIME        NOT NULL,
to_date     DATETIME        NOT NULL,
FOREIGN KEY (emp_no) REFERENCES employees (emp_no),
PRIMARY KEY (emp_no, from_date)
)

这是关联多方面的实体（使用嵌入式ID）：

@Entity
@Table(name = "salaries")
public class Salary {

    @EmbeddedId
    private EmpIdFromDatePK empId;

    @Column(name = "to_date", columnDefinition = "DATETIME")
    @Temporal(TemporalType.TIMESTAMP)
    private Date toDate;

    @Column(name = "salary")
    private Long salary;

    @ManyToOne(fetch = FetchType.LAZY)
    @Fetch(FetchMode.JOIN)
    @MapsId("empId")
    @JoinColumns({@JoinColumn(foreignKey = @ForeignKey(name = "salaries_ibfk_1"), name = "emp_no", referencedColumnName = "emp_no")})
    private Employee employee;

    public Salary() {
        super();
    }

    //...
}

关键课程：

@Embeddable
public class EmpIdFromDatePK implements Serializable {

    @Column(name = "emp_no")
    private Long empId;

    @Column(name = "from_date", columnDefinition = "DATETIME")
    @Temporal(TemporalType.TIMESTAMP)
    private Date fromDate;

    public EmpIdFromDatePK() {
        super();
    }

    //....
}

该协会一方的实体：

@Entity
@Table(name = "employees")
public class Employee {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "emp_no")
    private Long empId;

    //...

    @OneToMany(mappedBy = "employee")
    private List<Salary> salaryList;

    //...
}

问题：当我使用ManyToOne关联时（例如，在员工加入工资记录的选择中），在数据库中创建了第二个外键：

CONSTRAINT `FKjojacp79fphmajxrdll8fvf5o` FOREIGN KEY (`emp_no`) REFERENCES `employees` (`emp_no`),
CONSTRAINT `salaries_ibfk_1` FOREIGN KEY (`emp_no`) REFERENCES `employees` (`emp_no`)

问题：我该如何避免这种行为？

提前致谢

Answer 1

你可以尝试：

Template parse errors:
Can't bind to 'ngSwitchWhen' since it isn't a known property of 'form'.

Answer 2

JPA 2.1仅支持通过@ForeignKey注释定义外键。

所以如果你使用JPA旧版本而不是2.1，我认为你不能这样做

Hibernate / JPA自动创建外键而不是在多对一关联中使用现有外键

2 个答案: