Question

我遇到了关于hibernate和外键约束的问题。

我得到了以下场景（伪java代码）。我有一个父类（部门）

.Range("D" & (lastRowD + 1) & ":D" & lastRowE).Value = WBname

和子类（人）

@Entity
public class Department {

  @Id
  private Long id;

  @OneToMany(fetch = FetchType.EAGER, mappedBy = "department", cascade = CascadeType.ALL)
  List<Person> persons;

  public void addToPersons(Person p) {
    if (this.persons == null) {
      this.persons = new ArrayList<>();
    }
    this.persons.add(p);
    p.setDepartment(this);
  }

  public void setId(Long id) {
    this.id = id;
  }

}

完成后，存储库类

@Entity
public class Person {

  @Id
  private String name;

  @ManyToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
  private List<Person> followers;

  @ManyToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL, mappedBy = "followers")
  private List<Person> following;

  @ManyToOne(fetch = FetchType.LAZY)
  private Department department;

  public void addToFollowers(Person p) {
    if (this.followers == null) {
      this.followers = new ArrayList<>();
    }
    if (!this.followers.contains(p)) {
      this.followers.add(p);
    }
  }

  public void addToFollowing(Person p) {
    if (this.following == null) {
      this.following = new ArrayList<>();
    }
    if (!this.following.contains(p)) {
      this.following.add(p);
    }
  }

  public void setDepartment(Department department) {
    this.department = department;
  }

  public void setName(String name) {
    this.name = name;
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) return true;
    if (o == null || getClass() != o.getClass()) return false;
    Person that = (Person) o;
    return name != null ? name.equals(that.name) : that.name == null;
  }

}

导致异常的控制器

public interface DepartmentRepository extends CrudRepository<Department, Long> {}

我猜它会引发违规异常，因为部门d2尚未保存，但是可以在没有明确保存之前所有实体的情况下这样做吗？！

谢谢！

更新

完成代码。例外原因：

@RestController
public class MainController {

  @Autowired
  private DepartmentRepository departmentRepository;

  @RequestMapping("/")
  @ResponseBody
  public String index() {
    Department d1 = new Department();
    d1.setId(1L);

    Department d2 = new Department();
    d2.setId(2L);

    Person john = new Person();
    john.setName("John");

    Person alice = new Person();
    alice.setName("Alice");

    john.addToFollowers(alice);
    alice.addToFollowing(john);

    d1.addToPersons(john);
    d2.addToPersons(alice);

    departmentRepository.save(d1); // <-- throws violation exception 

    return "foo";
  }

}

Answer 1

@Entity(name = "department")     
class Department {

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

    @OneToMany(mappedBy = "department", cascade = { CascadeType.ALL })
    List<Person> person;

    // getter, setter...
}

@Entity(name = "Person") 
class Person {

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

    @ManyToOne
    @JoinColumn(name = "department_id")
    private Department department;

    // getter, setter... 
}


Department department = new Department();
Person p1 = new Person();
Person p2 = new Person();

p1.setDepartment(department);
p2.setDepartment(department);

personRepository.save(p1);
personRepository.save(p2);

Answer 2

在d.addToPersons(p1);实施中，请确保将部门设置为人，

public void addToPersons(Person person){
 person.setDepartment(this);
 this.persons.add(person);
}

同样适用于其他关系

Spring Hibernate Forgein Key Constraint

2 个答案: