JPA(Hibernate)代理類的hibernateLazyInitializer屬性系列化異常

　　今天在Spring Boot項目中使用JPA(Hibernate)進行數據庫訪問時，

spring:
  jpa:
    generate-ddl: false
    show-sql: true
    hibernate:
      ddl-auto: none
    open-in-view: true

　　查詢一個實體對象時出現異常：

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.xgclassroom.model.User$HibernateProxy$PpGM4JxY["hibernateLazyInitializer"])

　　仔細看了下報錯信息，發現直接原因是：jackson在對hibernate的持久化實體類的代理對象進行序列化時，代理類中的"hibernateLazyInitializer"屬性為空，觸發了系列化規划SerializationFeature.FAIL_ON_EMPTY_BEANS，即“出現空Bean時觸發序列化失敗”！

　　"hibernateLazyInitializer"屬性為空之所以為空是因為我們禁用了延遲加載（open-in-view: true），設為false又會引發no Session錯誤。

　　報錯信息中告訴我們可以通過禁用jackson的SerializationFeature.FAIL_ON_EMPTY_BEANS這條系列化規則來避免該異常(異常信息中的紅色字所示)，我們可以通過以下方式使用禁用了SerializationFeature.FAIL_ON_EMPTY_BEANS規則的新ObjectMapper替換默認的ObjectMapper的方法來達到目的：

@SpringBootApplication
@Configuration
public class ProviderUserApplication {
    public static void main(String[] args) {
        SpringApplication.run(ProviderUserApplication.class, args);
    }

    @Bean
    public ObjectMapper objectMapper() {
        return new ObjectMapper().disable(SerializationFeature.FAIL_ON_EMPTY_BEANS);
    }
}

　　

　　當然，也可以直接在相應的要實體類上通過@JsonIgnoreProperties忽略掉為空的屬性的系列化：

@Getter
@Setter
@Entity
@JsonIgnoreProperties(value = {"hibernateLazyInitializer"})
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column
    private String username;

    @Column
    private String name;

    @Column
    private Integer age;

    @Column
    private BigDecimal balance;
}

 

　　下面來看一下兩種方法重到的系列化結果樣例：

{"id":1,"username":"account1","name":"張三","age":20,"balance":100.00,"hibernateLazyInitializer":{}}

{"id":1,"username":"account1","name":"張三","age":20,"balance":100.00}