Question

我整个上午都在搜索这个问题，我无法获得有效的解决方案。

我有以下代码：

@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;

}

实体Post还有一个JPA @OneToMany注释，带有mappedBy和fetch LAZY。

但是，当我使用默认方法findAll / findOne来检索我的标签时，它还会选择检索帖子。

如何在不进行自定义查询的情况下检索标记实体的三个字段，该怎么办？我想使用JpaRepository提供的方法。

提前致谢。

修改：发布实体

@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 + "]";
  }

编辑：添加了TagController

@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 OUTPUT

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

编辑：

再次查看代码之后，应用程序的另一部分可能会尝试获取您的Post。调用Post的getter将告诉Hibernate获取实体。

即使您没有明确调用getter，有时也会发生这种情况。杰克逊在尝试撰写您的回复时可能正在调用它，或者甚至可以通过调用toString来调用它。例如，如果您在IDE中的断点处查看此响应，则IDE的调试器可能会在后台调用toString，以便使用对象的信息填充调试器UI。

在序列化您对{JSON的Post响应时，杰克逊可能会调用您的List<Tag>获取者。您可能想尝试添加正确的Jackson JSON解析器以支持Hibernate数据类型。

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

例如，尝试将数据类型添加到您的pom

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

为正确的模块添加一个bean。

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

你应该看看并确保你的Hibernate版本使用了正确的模块。

Answer 2

非常感谢您的回答。最后我可以解决这个问题。

它实际上存在于pom配置中，我忘了删除与Hibernate相关的插件，我不知道为什么，强制hibernate来获取嵌套对象。

谢谢大家的帮助。

JpaRepository findAll（）获取嵌套对象

2 个答案: