Json转换错误：No converter found for return value of type解决办法
调试一个maven构建的SSM项目，后端到前端转换成json报如下错：exception org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException解决办法：网上大佬说是json转换错误，所以需要添