mybatis的级联查询-懒加载遇到的序列化问题

不获取子查询的属性就不会触发子查询

例如：

    @RequestMapping(value = "/searchTravelTemplateById1", method = RequestMethod.GET)
    public void searchTravelTemplateById1(Integer id, HttpServletResponse response) {
        TourElectronicTravelTemplate travelTemplate = travelTemplateService.queryTravelTemplateById(id);
    }

如果有返回值，并且要序列化就会触发子查询，会使用同步查询所有结果，会有 N+1 问题

    @RequestMapping(value = "/searchTravelTemplateById1", method = RequestMethod.GET)
    public TourElectronicTravelTemplate searchTravelTemplateById1(Integer id, HttpServletResponse response) {
        TourElectronicTravelTemplate travelTemplate = travelTemplateService.queryTravelTemplateById(id);
        return travelTemplate;
    }

可能会出现一个bug:

2021-06-24 13:54:17.414 ----> [http-nio-8080-exec-1] ---> ERROR o.a.c.c.C.[.[localhost].[/].[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.apache.ibatis.executor.loader.javassist.JavassistProxyFactory$EnhancedResultObjectProxyImpl]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class org.apache.ibatis.executor.loader.javassist.JavassistProxyFactory$EnhancedResultObjectProxyImpl and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: com.tuniu.data.entity.vo.ResponseVo["data"]->com.tuniu.data.travle.entity.TourElectronicTravelTemplate_$$_jvste21_0["handler"])] with root cause
com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class org.apache.ibatis.executor.loader.javassist.JavassistProxyFactory$EnhancedResultObjectProxyImpl and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: com.tuniu.data.entity.vo.ResponseVo["data"]->com.tuniu.data.travle.entity.TourElectronicTravelTemplate_$$_jvste21_0["handler"])

可以在要返回的实体类属性上加入注解：

@JsonIgnoreProperties(value = {"handler"})

例如：

@JsonIgnoreProperties(value = {"handler"})
public class TourElectronicTravelTemplate {

在此标记不生成json对象的属性

因为jsonplugin用的是java的内审机制.hibernate会给被管理的pojo加入一个 handler 属性,jsonplugin会把 handler 也拿出来操作,并读取里面一个不能被反射操作的属性就产生了这个异常.