使用 JPA 的 Spring Boot OnetoMany

Question

我已经开始使用 Spring Boot 进行测试，以创建一个具有 简单的 crud 函数。我有两个实体类

公司.java

@Entity
@Table(name="Company_new")
public class Company {

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



public Set<User> getUsers() {
    return users;
}
public void setUsers(Set<User> users) {
    this.users = users;
}
public void setId(int id) {
    this.id = id;
}

@NotNull
@Column(name="name")
private String name;

@OneToMany(mappedBy="company",cascade=CascadeType.ALL)
private Set<User> users;


public Company(String name){
    this.name = name;
}
public Company(){

}

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

public String getName(){
    return name;
}

public int getId(){
    return id;
}
}

和 User.java

  @Entity
  @Table(name="user_new")
  public class User {
  @Id
  @Column
  @GeneratedValue(strategy = GenerationType.AUTO)
  private int idUser;

  @NotNull
  @Column
  private String name;

  @NotNull
  @Column
  private String userName;

  @NotNull
  @Column
  private String authLevel;

  @Column
  private String password;

  @ManyToOne
  @JoinColumn(name="idCompany")
  private Company company;

  // Public methods


  public Company getCompany(){
      return company;
  }

  public void setCompany(Company company){
      this.company = company;
  }




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

  public void setUserName(String userName){
      this.userName = userName;
  }

 public String getName(){
     return this.name;
 }

 public String getUsername(){
     return this.userName;
 }

 public String getPassword(){
     return this.password;
 }


  public String getAuthLevel() {
    return authLevel;
}

public void setAuthLevel(String authLevel) {
    this.authLevel = authLevel;
}

public String getUserName() {
    return userName;
}

public void setId(int idUser) {
    this.idUser = idUser;
}

public void setPassword(String password) {
    this.password = password;
}

public int getId(){
      return this.idUser;
  }




 }

我想与拥有许多用户的公司建立关系。 我尝试过像这样保存用户记录

@Autowired
CompanyDao companyDao;
@RequestMapping(value = "/user/create", method = RequestMethod.POST)

public @ResponseBody ResponseEntity createUser(@RequestBody User user) {


    try {
        Company c = companyDao.findOne(user.getCompany().getId());
        user.setCompany(c);
        userDao.save(user);

    } catch (Exception e) {

        return new ResponseEntity<>(null, HttpStatus.BAD_REQUEST);
    }

    return new ResponseEntity<>(user, HttpStatus.OK);
}

我的数据以我想要的方式保存在数据库中 但是当我尝试访问公司记录时，它会像这样加载

显然它在一个循环中加载关系并最终给出堆栈溢出错误。如何解决？

Answer 1

根据您想要的结果，您可以：

• 在public Set<User> getUsers() 上使用@JsonIgnore 以防止序列化用户集合或在public Company getCompany() 上使用@JsonIgnore 以防止公司序列化

• 在public Set<User> getUsers() 上使用@JsonManagedReference 和在public Company getCompany() 上使用@JsonBackReference，让Jackson 知道这是一个双向关系。

PS。如果您公开的 API 将被您无法控制的代码使用，请考虑 not exposing entities directly 但 mapping them to DTOs