Hibernate：无法删除外键

Question

有这两个类：

ddress.java：

@Embeddable
@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
public class Address {
    private String street;
    private String city;
    private String state;
    private String pincode;
}

User.java：

@Entity
@Data
public class User {
    @Id
    private int id;
    private String name;
    @ElementCollection
    private Set<Address> addresses = new HashSet<>();
}

演示应用程序。爪哇：

@Bean
CommandLineRunner dataLoader2(UserRepository userRepo){
  return  new CommandLineRunner() {
    @Override
    public void run(String... args) throws Exception {
      User u = new User();
      u.setName("Some random name");
      Address a1 = Address.builder()
          .street("First Street")
          .city("first city")
          .state("first state")
          .pincode("100001")
          .build();
      Address a2 = Address.builder()
          .street("Second Street")
          .city("Second city")
          .state("second state")
          .pincode("200002")
          .build();
      u.setAddresses(new HashSet<>(Arrays.asList(a1, a2)));
      userRepo.save(u);
    }
  };
}

运行时，如果失败，出现此错误：

GenerationTarget遇到异常接受命令：通过JDBC语句执行DDL“更改表user_addresses删除外键FKfm6x520mag23hvgr1oshaut8b”时出错

然而，最终的表格被创建：描述用户地址：

+---------+--------------+------+-----+---------+-------+
| Field   | Type         | Null | Key | Default | Extra |
+---------+--------------+------+-----+---------+-------+
| user_id | int          | NO   | MUL | NULL    |       |
| city    | varchar(255) | YES  |     | NULL    |       |
| pincode | varchar(255) | YES  |     | NULL    |       |
| state   | varchar(255) | YES  |     | NULL    |       |
| street  | varchar(255) | YES  |     | NULL    |       |
+---------+--------------+------+-----+---------+-------+

描述用户：

+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id    | int          | NO   | PRI | NULL    |       |
| name  | varchar(255) | YES  |     | NULL    |       |
+-------+--------------+------+-----+---------+-------+

为什么jdbc不能删除表user\u addresses中的外键user\u id？如何让jdbc做到这一点？

Answer 1

"USER"是MySQL中的保留字，这可能是问题的根本原因。请更改User实体的名称，或向其添加@Table注释，并定义不同的名称。

参考文件：

• https://dev.mysql.com/doc/refman/5.7/en/keywords.html
• https://dev.mysql.com/doc/refman/8.0/en/keywords.html