Hibernate多对多关联含额外列查询报错：未知列问题

我在使用Hibernate处理带有额外列的多对多关联时遇到问题，以下是我的代码：

@Entity
public class TransactionEntity extends AbstractBaseEntity {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long transactionId;
  
  /* some fields*/

  @OneToMany(mappedBy = "transaction", fetch = FetchType.LAZY)
  private List<TransactionTagEntity> tags;
}

@Entity
public class TagEntity extends AbstractBaseEntity {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long tagId;

  /* some fields*/

  @OneToMany(mappedBy = "tag", fetch = FetchType.LAZY)
  private List<TransactionTagEntity> transactions;
}

@Entity
public class TransactionTagEntity extends AbstractBaseEntity {
  @EmbeddedId
  private TransactionTagPk pk;

  @ManyToOne
  @MapsId("transactionId")
  private TransactionEntity transaction;

  @ManyToOne
  @MapsId("tagId")
  private TagEntity tag;
}

@Embeddable
public class TransactionTagPk implements Serializable {
  @Column(name = "transaction_id")
  private Long transactionId;

  @Column(name = "tag_id")
  private Long tagId;
}

当我尝试查询关联了标签的交易（或关联了交易的标签）时，收到如下错误：

Unknown column 't2_0.tag_tag_id' in 'on clause'

或

Unknown column 't2_0.transaction_transaction_id' in 'on clause'

我从未定义过这些列，这是怎么回事？

编辑补充 #

以下是Hibernate生成的查询语句示例：

select t1_0.transaction_transaction_id, t1_0.tag_tag_id, t2_0.tag_id, t2_0.name, t2_0.note, t2_0.time_create, t2_0.time_update, t2_0.user_create_id, t2_0.user_id, t2_0.user_update_id, t1_0.time_create, t1_0.time_update, t1_0.user_create_id, t1_0.user_update_id from transaction_tag t1_0 left join tag t2_0 on t2_0.tag_id=t1_0.tag_tag_id where t1_0.transaction_transaction_id=?

问题原因 #

Hibernate错误生成了transaction_transaction_id、tag_tag_id这类拼接列名，本质是它默认将关联实体的属性名与对应主键名拼接，比如把TransactionTagEntity里的transaction属性和该属性的主键transactionId组合成transaction_transaction_id，但你的中间表transaction_tag实际列名是transaction_id和tag_id，两者不匹配导致报错。

修复步骤 #

需要在TransactionTagEntity的@ManyToOne注解上显式指定关联列名，明确告诉Hibernate中间表对应的外键列：

修改后的TransactionTagEntity代码如下：

@Entity
public class TransactionTagEntity extends AbstractBaseEntity {
  @EmbeddedId
  private TransactionTagPk pk;

  @ManyToOne
  @MapsId("transactionId")
  @JoinColumn(name = "transaction_id") // 显式指定外键列名
  private TransactionEntity transaction;

  @ManyToOne
  @MapsId("tagId")
  @JoinColumn(name = "tag_id") // 显式指定外键列名
  private TagEntity tag;
}

额外说明 #

虽然你已经在TransactionTagPk中用@Column指定了列名，但Hibernate处理关联映射时仍会默认按属性名+主键名生成外键列名。因此必须通过@JoinColumn明确指定与中间表一致的列名，这样生成的SQL就会正确使用transaction_id和tag_id，避免错误的拼接列名。

内容的提问来源于stack exchange，提问作者Mark116