时间戳

首页 > 解决方案 > Hibernate 无法将许多学生映射到一个班级

java - Hibernate 无法将许多学生映射到一个班级

问题描述

我有 2 个简单的实体：学生和班级。我想发布一个学生，在其中指定它所属的类，但我陷入了休眠映射。

类模型.class

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


@Id
@Column(name = "id")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;

@NotEmpty
@Size(max = 20)
@Column(name = "name")
private String name;

@Column(name = "tables")
private int tables;

@Column(name = "chairs")
private int chairs;

@Column(name = "teacher")
private String teacher;
(getters + setters)

学生模型

@Entity
@Table(name = "student")
public class StudentModel implements Serializable {

@Id
@Column(name = "student_id")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int student_id;

@NotEmpty
@Column(name = "name")
@Size(max = 50)
private String name;

@Column(name = "age")
private int age;

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "id")
private ClassModel classModel;
(getters + setters)
}

StudentController.java

...
@Autowired
private StudentService studentService;

@Autowired
private ClassService classService;

@PostMapping(value = "/save")
public StudentModel save(@RequestBody StudentModel studentModel){
    ClassModel classModel = classService.findById(studentModel.getClassId()).get();
    studentModel.setClassModel(classModel);
    return studentService.save(studentModel);
}
...

但是，当我向 Postman 提出以下请求时：

{
    "name": "some name",
    "age": 12,
    "class_id": 1
}

我从休眠中收到以下错误：

Column 'class_id' cannot be null

我的休眠映射中的错误在哪里？

标签： javajsonspringspring-data-jpaspring-data

解决方案

这就是我如何让工作加入休眠状态。看一看：

TrainingEntity.java

@Id
private Integer id;

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "animal_id", nullable = false, insertable = false, updatable = false)
private AnimalEntity animalEntity;

@Column(name = "animal_id")
private Integer animalId;

AnimalEntity.java

@Id
private Integer id;

@OneToMany(mappedBy = "animalEntity", fetch = FetchType.LAZY)
private List<TrainingEntity> trainingEntityList = new ArrayList<>();

所以这里是 AnimalEntity 和 TrainingEntity 之间的连接。AnimalEntity 有一个 TrainingEntity 列表。

推荐阅读