Spring 启动实体无法使用 ManyToOne 添加实体

Question

我的学习项目中有这些实体，但我不明白为什么我无法添加员工：

@Entity
@Table(name = "department")
@Data
public class Department {

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

    @Column(name = "department_name")
    @JsonProperty("department_name")
    private String department_name;
}

@Entity
@Table(name = "office")
@Data
public class Office {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "office_id")
    @JsonProperty("office_id")
    private Long office_id;

    @Column(name = "office_name")
    @JsonProperty("office_name")
    private String office_name;
}

@Entity
@Table(name = "employee")
@Data
public class Employee {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "employee_id")
    @JsonProperty("employee_id")
    private Long employee_id;

    @Column(name = "employee_name")
    @JsonProperty("employee_name")
    private String employee_name;

    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "department_id")
    private Department department;

    private Long office_id;
}

使用 Postman，我发送 POST 以使用 Spring 数据 REST 生成的 http://localhost:9096/employee 端点在部门 'engineer' 中添加一名员工 [=27] =]正文：

{
    "employee_name": "Tim",
    "office_id" : 1,
    "department": {
        "department_id": 1
    }
}

我总是遇到异常："Column 'department_id' cannot be null"。

解决这个问题的正确方法应该是什么？

完整的项目可以在 https://github.com/txt8888/sping-mysql-db

找到

Answer 1

似乎 department_id 在您的数据库中不存在，或者您的 ManyToOne 配置不正确。所以它会导致错误。可以参考下面这个ManyToOne关系

@Entity
@Table(name = "course")
public class Course  implements Serializable{

    private int id;
    private Set<Student> students;

    public Course(){

    }
    @OneToMany(mappedBy = "course", cascade = CascadeType.ALL)
    public Set<Student> getStudents() {
        return students;
    }
}

@Entity
public class Student implements Serializable{
    private int id;
    private Course course;

    public Student() {

    }

    @ManyToOne
    @JoinColumn(name = "course_id")
    public Course getCourse() {
        return course;
    }
}

您可以从 post Spring Boot JPA One to Many Relationship Mapping

查看工作示例

Answer 2

我不确定 Spring Data REST 是否支持像那样嵌入部门（通过使用 { "department_id": 1 }。默认情况下，如果你想 link 资源（例如。 a department) to another (eg. an employee), 你使用资源link，例如：

{
    "employee_name": "Tim",
    "office_id" : 1,
    "department": "http://localhost:9096/departments/1"
}

这将创建一个新员工 linked 到 ID 为 1 的部门。如果你想 link 员工到一个新部门，你可能必须先创建部门， link 以同样的方式发送给员工。

Spring 启动实体无法使用 ManyToOne 添加实体

Spring boot Enity failed to add entity with ManyToOne

jpa

crud

spring-data-rest

spring-boot