1.出错地方

    使用SpringBoot JPA获取的对象返回前端时报错：Debug的时候在Controller以下都没有问题（整个类中所有属性都有值），在返回前端的Debug时，发现报错在ServletInvocableHandlerMethod中，处理返回值时报错：

     随后，查看此时的数据和异常信息：

2.异常信息

     下面是主要的异常信息：

2019-07-28 21:45:39.117 ERROR 21008 --- [nio-8803-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet 
[dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.http.converter.HttpMessageConversionException: 
Type definition error: 
[simple type, class org.hibernate.proxy.pojo.bytebuddy.ByteBuddyInterceptor]; 
nested exception is 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.hand.area.entity.Country$HibernateProxy$FHGzOBvp["hibernateLazyInitializer"])] 
with root cause
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.hand.area.entity.Country$HibernateProxy$FHGzOBvp["hibernateLazyInitializer"])
at com.fasterxml.jackson.databind.exc.InvalidDefinitionException
.from(InvalidDefinitionException.java:77) ~[jackson-databind-2.9.9.jar:2.9.9]

3.解决办法

    在需要返回的类添加注解：

@JsonIgnoreProperties({"hibernateLazyInitializer","handler"})

4.总结

    从注解中理解是Hibernate懒加载初始化器，具体也不太清楚，对应的解决办法我是参考：参考链接。里面也没有太具体的说明