无法写入 JSON：未能一对一地延迟初始化角色集合

Question

我有以下代码... 这是一个用户有一面墙的应用程序，而那面墙上可以有几个游戏。

@Entity
@Table(name = "tb_user")
public class User implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;

    @OneToOne(mappedBy = "user",fetch = FetchType.EAGER)
    private Mural mural;

    public User() {

    }

    public User(Long id, String name, Mural mural) {
        this.id = id;
        this.name = name;
        this.mural = mural;

     //getters and setters...
    }

@Entity
@Table(name = "tb_mural")
public class Mural implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;

    @ManyToMany
    @JoinTable(name = "tb_mural_games",
            joinColumns = @JoinColumn(name = "mural_id"),
            inverseJoinColumns = @JoinColumn(name = "games_id"))
    private Set<Game> games = new HashSet<>();

    @OneToOne
    @JoinColumn(name = "user_id")
    private User user;

    public Mural() {

    }

    public Mural(Long id, String name, User user) {
        this.id = id;
        this.name = name;
        this.user = user;
    }
 
    //getters and setters...

还有下面的请求……

 @GetMapping
    public ResponseEntity<List<User>> findAll(){
        List<User> list = repository.findAll();
        return ResponseEntity.ok().body(list);
    }

但我有以下错误...

 Resolved [org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: failed to lazily initialize a collection of role... continue...

我尝试使用 FETCH.EAGER 但它不起作用，它只有在我使用 jsonignore 时才有效，但我希望它在用户请求中返回“壁画”。

用户请求数据是这些=

[
    {
        "id": 1,
        "name": "Anderson Conforto"
    },
    {
        "id": 2,
        "name": "Airton Conforto"
    }
]

但是使用jsonignore，它会忽略壁画类数据，这不是我想要的。

Answer 1

将JsonIgnore放在Mural类中

@OneToOne
@JoinColumn(name = "user_id")
private User user;

还要尽量避免将实体直接返回给最终用户。尝试将实体映射到 DTO 或使用投影 (https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#projections)。