Circular view path [addKnowledge]: would dispatch back to the current handler URL

报错日志：

{"timestamp":1526565246776,"status":500,"error":"Internal Server Error","exception":"javax.servlet.ServletException","message":"Circular view path [addKnowledge]: would dispatch back to the current handler URL [/addKnowledge] again. Check your ViewResolver setup! (Hint: This may be the result of an unspecified view, due to default view name generation.)","path":"/addKnowledge"}

解决方案：
添加@ResponseBody 注解：

@PostMapping("/addKnowledge")
@ResponseBody