无法反序列化异常 spring 引导数据 jpa

Question

我正在使用 postgres 数据库并使用 spring 数据 jpa 编写后端代码。

社区表：

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
@Table(name = "community_table")
@Entity
public class CommunityTable {
    @Id
    @GeneratedValue
    @Column(name = "community_id")
    private Integer communityId;

    @Column(name = "community_name", unique = true, nullable = false)
    private String communityName;

    @Column(name = "creation_date", nullable = false)
    private Date creationDate;

    @Column(name = "rules", columnDefinition = "text")
    private String[] rules;

    @ManyToOne
    @JoinColumn(name = "creator_id", nullable = false)
    private UserTable creatorId;

    @ManyToOne
    @JoinColumn(name = "current_owner", nullable = false)
    private UserTable currentOwner;
}

用户表：

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
@Table(name = "user_table")
@Entity
public class UserTable {
    @Id
    @GeneratedValue
    @Column(name = "user_id", nullable = false)
    private Integer userId;

    @Column(name = "email", nullable = false, unique = true)
    private String email;

    @Column(name = "username", nullable = false, unique = true)
    private String username;

    @Column(name = "join_date", nullable = false)
    private Date joinDate;

    @Column(name = "hashed_password", nullable = false)
    private String hashedPassword;

    @Column(name = "password", nullable = false)
    private String password;

    @Column(name = "last_logged_in", nullable = false)
    private Date lastLoggedIn;

    @OneToMany(mappedBy = "creatorId")
    private List<CommunityTable> creatorCommunity;

    @OneToMany(mappedBy = "currentOwner")
    private List<CommunityTable> ownerCommunity;
}

Controller 代码失败：

@GetMapping("/community")
    public ResponseEntity getAllCommunities(){
        try{
            return new ResponseEntity<>(userService.getAllCommunities(), HttpStatus.OK);
        }catch (Exception e){
            log.error(e.toString());
            return new ResponseEntity<String>("Unable to fetch all communities", HttpStatus.CONFLICT);
        }
    }

导致上述 controller 方法失败的服务代码：

public List<CommunityTable> getAllCommunities() throws Exception{
        try{
            return communityTableRepository.findAll();
        }catch (Exception e){
            log.error(e.toString());
            throw new Exception("Unable to fetch community due to: "+e.toString());
        }
    }

例外：

Hibernate: select communityt0_.community_id as communit1_0_, communityt0_.community_name as communit2_0_, communityt0_.creation_date as creation3_0_, communityt0_.creator_id as creator_5_0_, communityt0_.current_owner as current_6_0_, communityt0_.rules as rules4_0_ from community_table communityt0_
2022-01-05 22:34:14.989 ERROR 20231 --- [nio-8080-exec-1] c.e.redditbackend.service.UserService    : org.springframework.orm.jpa.JpaSystemException: could not deserialize; nested exception is org.hibernate.type.SerializationException: could not deserialize
2022-01-05 22:34:14.990 ERROR 20231 --- [nio-8080-exec-1] c.e.r.controller.UserController          : java.lang.Exception: Unable to fetch community due to: org.springframework.orm.jpa.JpaSystemException: could not deserialize; nested exception is org.hibernate.type.SerializationException: could not deserialize

不要介意log.error。 我已经用@Log4j2 注释了服务和 controller class 所以这不是这里的问题。 由于某种原因，我无法获取社区表列表。

为什么会出现上述异常的任何想法。

Answer 1

这里的问题是由以下原因引起的：

@Column(name = "rules", columnDefinition = "text")
private String[] rules; // <-- column only holds a single string, not an array!

使用此 columnDefinition，DB 列不包含字符串数组而是单个字符串，因此它只有在这样定义时才会起作用：

@Column(name = "rules", columnDefinition = "text")
private String rules; // <-- no array!

---

如果您想要多个（有序）字符串，您可以切换到@ElementCollection ：

@ElementCollection
@OrderColumn
@Column(columnDefinition = "text")
private List<String> strings; // (<-- not an array, but a list)

---

或者，如果您确实需要一个数组和/或您想在没有集合表的情况下将所有值存储在单个列中，您可以使用hibernate-types ：

implementation 'com.vladmihalcea:hibernate-types-55:2.14.0'

实体：

@TypeDef(
    name = "string-array", 
    typeClass = StringArrayType.class
)
class MyEntity { // ...

  @Type( type = "string-array" )
  @Column(columnDefinition = "text[]") // <-- column matches entity attribute type
  private String[] strings;

// ...
}