无法反序列化异常春季启动数据jpa

Question

我使用的是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;
}

失败的控制器代码：

@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);
}
}

导致上述控制器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注释了服务和控制器类，所以这不是这里的问题。由于某种原因，我无法获取社区表的列表

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!

使用这个columnDefinition，DB列不包含字符串数组，而是包含一个字符串，因此只有这样定义才能工作：

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

---

如果您想要有多个(有序的(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/或希望将所有值存储在没有集合表的单列中，则可以使用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;
// ...
}