SpringBoot + JPA问题汇总

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name ‘baseJpaRepository‘: Invocation of init method failed; nested exception is java.lang.IllegalArgumentException: Not a managed type: class java.lang.Object
...
Caused by: java.lang.IllegalArgumentException: Not a managed type: class java.lang.Object

***************************
APPLICATION FAILED TO START
***************************
...
The injection point has the following annotations:
    - @org.springframework.beans.factory.annotation.Autowired(required=true)
...

@Entity
@Table(name = "al_config")
public class ConfigDTO extends BaseDTO { ... }

Caused by: org.hibernate.MappingException: Could not determine type for: com.asing1elife.teamnote.dto.ProjectGroupDTO, at table: al_project, for columns: [org.hibernate.mapping.Column(project_group)]

@Entity
@Table(name = "al_project")
public class ProjectDTO extends BaseDTO {
    @Column
    private ProjectGroupDTO projectGroup;
}

java.sql.SQLSyntaxErrorException: Table ‘asl_station.hibernate_sequence‘ doesn‘t exist

public class BaseDTO {
    @Id
    @GeneratedValue
    private Long id = 0L;
}

public class BaseDTO {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id = 0L;
}

修改JPA的字段命名规则为驼峰式

异常表现

1. 在实体类和数据库中对应的字段都是createTime，但是JPA在连接对应表时却抛出如下错误
2. 因为JPA默认的字段映射规则是下划线风格

Caused by: java.sql.SQLSyntaxErrorException: Unknown column ‘create_time‘ in ‘field list‘

@Column
private Date createTime = DateUtil.getSysDate();

解决方式

1. 在配置文件中指定JPA的字段映射规则为驼峰式即可

spring:
  jpa:
    hibernate:
      naming:
        physical-strategy: org.hibernate.boot.model.naming.PhysicalNamingStrategyStandardImpl

获取单个实体类JSON转换异常

异常表现

1. Hibernate的获取单个实体类数据后，为会每个实体类添加一个hibernateLazyInitializer属性，改属性在进行JSON转换时抛出异常

com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class org.hibernate.proxy.pojo.bytebuddy.ByteBuddyInterceptor and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: com.asing1elife.teamnote.core.bean.ResponseData["data"]->com.asing1elife.teamnote.dto.OrganizationDTO$HibernateProxy$f3Tr4vBI["hibernateLazyInitializer"])

解决方式一

1. 在实体类顶部添加@JsonIgnoreProperties("hibernateLazyInitializer")，确保数据转换时会过滤掉休眠生成的属性

   @JsonIgnoreProperties("hibernateLazyInitializer")
   public class BaseDTO { ... }

解决方式二

1. 上述根据报错disable SerializationFeature.FAIL_ON_EMPTY_BEANS可以尝试将JSON转换时的以下属性设置为false

spring:
  jackson:
    serialization:
      fail-on-empty-beans: false

前端数据传递到后端过程中，反序列失败

异常表现

1. 杰克逊反序列化时需要无参构造函数，因为数据对应的实体类某个对象属性没有无参构造函数，就会抛出以下异常

(although at least one Creator exists): cannot deserialize from Object value (no delegate- or property-based Creator)

解决方式

1. 检查实体类自身以及所有对象属性，为每个对象添加对应的无参构造函数即可解决
2. 自参考博客园