loadAll() 和 loadById(Long id) 时 JSON 序列化的差异

Question

我创建了文件夹class (java springboot)，它描述了用于书签管理的多级文件夹结构：

@Entity
@Setter
@Getter
@NoArgsConstructor
@AllArgsConstructor
**public class Folder** implements Serializable {

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

    @ManyToOne(cascade = CascadeType.PERSIST)
    @JoinColumn(name = "parent_id")
    @JsonIdentityInfo(
            generator = ObjectIdGenerators.PropertyGenerator.class,
            property = "id")
    private Folder parent;

    @OneToMany(mappedBy = "parent", cascade = CascadeType.PERSIST)
    private List<Folder> children = new ArrayList<>();

    private String name;

    private String path;

    @OneToMany(mappedBy = "folder", cascade = CascadeType.PERSIST)
    @JsonManagedReference
    private List<Bookmark> bookmarkList = new ArrayList<>();
}

@Entity
@Setter
@Getter
@NoArgsConstructor
@AllArgsConstructor
**public class Bookmark** implements Serializable {

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

    private String name;

    private String url;

    private String description;

    /**
     * parent folder
     */
    @ManyToOne
    @JsonBackReference
    private Folder folder;
}

我的问题是，当 loadAll() 和 loadById(Long id):

时，我可以看到序列化 JSON 的差异

@Service
@Transactional
**public class FolderService** {

    private FolderRepo folderRepo;

    @Autowired
    public FolderService(FolderRepo folderRepo) {
        this.folderRepo = folderRepo;
    }

    public void save(Folder folder) {
        folderRepo.save(folder);
    }

    public List<Folder> loadAll() {
        List<Folder> folderList = folderRepo.findAll();
        return folderList;
    }

    public Folder loadById(Long id) {
        Folder folder = folderRepo.findById(id).get();
        return folder;
    }

}

@RestController
@RequestMapping("/bookmarks-app")
**public class FolderControllerRest** {

    private FolderService folderService;

    @Autowired
    public FolderControllerRest(FolderService folderService) {
        this.folderService = folderService;
    }

    @GetMapping("/folders/all")
    public List<Folder> getFolderListAll() {
        List<Folder> folderList = folderService.loadAll();
        return folderList;
    }

    @GetMapping("/folder/{id}")
    public Folder getFolderById(
            @PathVariable(name = "id") String id
    ) {
        if (!"undefined".equals(id)) {
            Long folderId = Long.parseLong(id);
            return folderService.loadById(folderId);
        } else return null;
    }

}

也就是说，区别是ex。在 folder.id=2.

当我全部加载时使用 ajax:

$.ajax({
        url: "/bookmarks-app/folders/all",
        data: {},
        method: "GET",
        dataType: "JSON"
    });

父实体序列化为它的“id”号（如我所愿），

但是当使用 ajax:

 $.ajax({
    url: "/bookmarks-app/folder/2",
   data: {},
    method: "GET",
   dataType: "JSON"
 })

父实体序列化为对象（下面的屏幕截图）。

screenshoot

Answer 1

我认为你误用了@JsonIdentityInfo，文档说

@JsonIdentityInfo allows to serialize a POJO by id when it is encountered second time during serialization.

然后在 'list' 模式下你得到 id，在单一模式下你得到整个对象。

也许你应该使用 TypeAdaptor 来获取 id

loadAll() 和 loadById(Long id) 时 JSON 序列化的差异

Differences in JSON serialization when loadAll() and loadById(Long id)

java

serialization

json

spring-boot

spring-restcontroller