JpaRepository findAll() 正在獲取嵌套對象

Question

我整個上午都在搜索這個問題，但找不到有效的解決方案。

我有以下代碼：

@Entity
@Getter
@Setter
@ToString
@EqualsAndHashCode
@Table(name = Tag.TABLE_NAME)
@NoArgsConstructor
public class Tag {
  static final String TABLE_NAME = "blog_tags";
  private static final String ID_TAG = "idTag";
  private static final String FIELD_TAG = "tag";
  private static final String FK_POST = "FK_Post";

  @Id
  @NotNull
  @Column(name = ID_TAG, unique = true)
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long id;

  @NotNull
  @Column(name = FIELD_TAG, unique = true)
  private String tagName;

  @ManyToOne(fetch = FetchType.LAZY)
  @JoinColumn(name = FK_POST, insertable = false, updatable = false)
  private Post post;

  @NotNull
  @Column(name = FK_POST)
  private Long fkPost;

}

實體 Post 也有一個 JPA @OneToMany 注釋，帶有一個 mappingBy 和 fetch LAZY。

但是，當我使用默認方法 findAll/findOne 檢索我的標簽時，它也會選擇檢索帖子。

如何只檢索標簽實體的三個字段而不進行自定義查詢？ 我想使用 JpaRepository 提供的方法。

提前致謝。

編輯：發布實體

@Entity
@NoArgsConstructor
@Table(name = Post.TABLE_NAME)
public class Post {
  static final String POST_AUTHOR_ENTITYGRAPH = "Post.author";
  private static final String MAPPED_BY_POST = "post";
  static final String TABLE_NAME = "blog_posts";
  private static final String FIELD_POST_VISITS = "post_visits";
  private static final String FIELD_POST_MODIFIED = "post_modified";
  private static final String FIELD_POST_ENABLED = "post_enabled";
  private static final String FIELD_POST_DATE = "post_date";
  private static final String FIELD_POST_CONTENT = "post_content";
  private static final String FIELD_COMMENTS_ENABLED = "comments_enabled";
  private static final String FIELD_TITLE = "post_title";
  private static final String ID_POST = "idPost";
  private static final String FK_AUTHOR = "FK_Author";

  @NotNull
  @Column(name = FIELD_COMMENTS_ENABLED)
  private boolean commentsEnabled;

  @NotNull
  @Column(name = FIELD_POST_CONTENT, columnDefinition = "LONGTEXT")
  private String postContent;

  @NotNull
  @Column(name = FIELD_POST_DATE, unique = true, columnDefinition = "DATETIME")
  private LocalDateTime postDate;

  @NotNull
  @Column(name = FIELD_POST_ENABLED)
  private boolean postEnabled;

  @Id
  @Column(name = ID_POST, unique = true)
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long id;

  @NotNull
  @Column(name = FIELD_POST_MODIFIED, columnDefinition = "DATETIME")
  private LocalDateTime postModified;

  @NotNull
  @Column(name = FIELD_TITLE, unique = true)
  private String postTitle;

  @NotNull
  @Column(name = FIELD_POST_VISITS)
  private Long postVisits;

  @ManyToOne(fetch = FetchType.LAZY)
  @JoinColumn(name = FK_AUTHOR, insertable = false, updatable = false)
  private User author;

  @NotNull
  @Column(name = FK_AUTHOR)
  private Long fkAuthor;

  @ManyToMany(fetch = FetchType.LAZY)
  @JoinTable(name = "blog_posts_categories", joinColumns = @JoinColumn(name = ID_POST, referencedColumnName = ID_POST), //
      inverseJoinColumns = @JoinColumn(name = Category.ID_CATEGORY, referencedColumnName = Category.ID_CATEGORY))
  private Set<Category> categories;

  @OneToMany(mappedBy = MAPPED_BY_POST, fetch = FetchType.LAZY)
  private Set<Image> images;

  @OneToMany(mappedBy = MAPPED_BY_POST, fetch = FetchType.LAZY)
  private Set<Tag> tags;

 // Autogenerated getters & setters

  @Override
  public String toString() {
    return "Post [commentsEnabled=" + commentsEnabled + ", postContent=" + postContent
        + ", postDate=" + postDate + ", postEnabled=" + postEnabled + ", id=" + id
        + ", postModified=" + postModified + ", postTitle=" + postTitle + ", postVisits="
        + postVisits + "]";
  }

編輯：添加了標簽控制器

@Api(tags = "Tags")
@RestController
@RequestMapping(TagController.REST_API)
public class TagController {

  static final String REST_API = "/tags";
  public static final String ID_TAG = "ID_TAG";
  public static final String PARAM_URL = "/{" + ID_TAG + "}";

  private final JpaRepository<Tag,Long> repository;
  private final TagMapper mapper;

  @Autowired
  TagController(final JpaRepository<Tag,Long> repository,
      final TagMapper mapper) {
    this.repository = repository;
    this.mapper = mapper;
  }

  @ApiOperation(value = "Find all the tags from database.", tags = "tags")
  @GetMapping(produces = "application/json")
  public List<TagDto> getAllTags() {
    return mapper.entityToDtoList(repository.findAll());
  }

}

SQL 輸出

Hibernate: select tag0_.idTag as idTag1_6_, tag0_.FK_Post as FK_Post2_6_, tag0_.tag as tag3_6_ from blog_tags tag0_
Hibernate: select post0_.idPost as idPost1_3_0_, post0_.FK_Author as FK_Autho3_3_0_, post0_.comments_enabled as comments2_3_0_, post0_.post_content as post_con4_3_0_, post0_.post_date as post_dat5_3_0_, post0_.post_enabled as post_ena6_3_0_, post0_.post_modified as post_mod7_3_0_, post0_.post_title as post_tit8_3_0_, post0_.post_visits as post_vis9_3_0_ from blog_posts post0_ where post0_.idPost=?
Hibernate: select user0_.idUser as idUser1_7_0_, user0_.user_email as user_ema2_7_0_, user0_.passwordHash as password3_7_0_, user0_.FK_Role as FK_Role8_7_0_, user0_.passwordSalt as password4_7_0_, user0_.user_enabled as user_ena5_7_0_, user0_.user_name as user_nam6_7_0_, user0_.user_website as user_web7_7_0_ from blog_user user0_ where user0_.idUser=?
Hibernate: select userrole0_.idUserRole as idUserRo1_8_0_, userrole0_.user_role as user_rol2_8_0_ from blog_user_roles userrole0_ where userrole0_.idUserRole=?

Answer 1

編輯：

再次查看代碼后，應用程序的另一部分可能正在嘗試獲取您的Post 。 為Post調用 getter 將告訴 Hibernate 獲取實體。

即使您沒有明確調用 getter，有時也會發生這種情況。 Jackson 在嘗試編寫您的響應時可能會調用它，或者甚至可以通過調用toString來調用它。 例如，如果您在 IDE 的斷點處查看此響應，則 IDE 的調試器可能會在幕后調用 toString，以便使用您的對象信息填充調試器 UI。

在將您的List<Tag>響應序列化為 JSON 時，Jackson 很可能正在調用您的Post getter。 您可能想嘗試添加正確的 Jackson JSON 解析器以支持 Hibernate 數據類型。

https://github.com/FasterXML/jackson-datatype-hibernate

例如，嘗試將數據類型添加到您的 pom

<dependency>
    <groupId>com.fasterxml.jackson.datatype</groupId>
    <artifactId>jackson-datatype-hibernate5</artifactId>
</dependency>

並為正確的模塊添加一個 bean。

@Bean
public Module hibernateModule() {
    return new Hibernate5Module();
}

您應該查看一下並確保您使用的是適合您的 Hibernate 版本的正確模塊。

Answer 2

非常感謝您的回答。 最后我可以解決這個問題。

它實際上駐留在 pom 配置中，我忘記刪除與 Hibernate 相關的插件，我不知道為什么，強制 Hibernate 獲取嵌套對象。

謝謝大家幫助我。