java - AnnotationException 引用的属性不是 (One|Many)ToOne

Question

我试图建立一对一的关系。但我得到错误:

AnnotationException Referenced property not a (One|Many)ToOne
on
com.student.information.service.Department.departmentId in mappedBy of com.student.information.service.DepartmentHead.department

这两个实体几乎完全相同。部门可以没有部门负责人。

部门.Java

@Entity
@Table(name="department", catalog="student")
public class Department {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Integer departmentId;

    @Column(name="dept_name")
    private String departmentName;

    @OneToMany(mappedBy="department",cascade = CascadeType.ALL)
    private List<Student> student; 

    @OneToOne(targetEntity=Department.class)
    private DepartmentHead departmenthead;
}       

DepartmentHead.java

@Entity
@Table(name="departmenthead", catalog = "student")
public class DepartmentHead {

    //This is mapped with the department id

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int id;

    @Column(name="headname")
    private String headName;

    @OneToOne(mappedBy = "departmentId",fetch = FetchType.LAZY,cascade=CascadeType.ALL)
    @JoinColumn(name="dept_id")
    private Department department;  
}

Caused by: org.hibernate.AnnotationException: 引用的属性不是 (One|Many)ToOne:

有人可以指出我犯了什么错误的正确方向吗？过去 2 天我一直在苦苦挣扎，无法找出问题的解决方案。在此先感谢您的帮助。

Answer 1

您的映射设置不正确。 Hibernate 提示没有名为 departmentId 的字段可用于建立一对一或多对关系，这是正确的。

您想像这样映射您的值(value)观。

部门.Java

@Entity
@Table(name="department", catalog="student")
public class Department {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Integer departmentId;

    @OneToOne
    @JoinColumn(name = "id")
    private DepartmentHead departmenthead;
}       

DepartmentHead.java

@Entity
@Table(name="departmenthead", catalog = "student")
public class DepartmentHead {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int id;

    @OneToOne(mappedBy = "departmenthead")
    private Department department;  
}

您将 DepartmentHead 中的 Department 字段指向 Department 内的 DepartmentHead 字段。 Hibernate 会整理出要使用的 ID，您不必在实际链接中指定它。