问题
导入excel文件时，偶发bug:
org.springframework.web.multipart.MultipartException: Could not parse multipart servlet request; nested exception is java.io.IOException: The temporary upload location [C:\Users\AppData\Local\Temp\tomcat.4266029690466887869.8037\work\Tomcat\localhost\ROOT] is not valid
at org.springframework.web.multipart.support.StandardMultipartHttpServletRequest.parseRequest(StandardMultipartHttpServletRequest.java:112)
at org.springframework.web.multipart.support.StandardMultipartHttpServletRequest.<init>(StandardMultipartHttpServletRequest.java:86)
at org.springframework.web.multipart.support.StandardServletMultipartResolver.resolveMultipart(StandardServletMultipartResolver.java:79)
at org.springframework.web.servlet.DispatcherServlet.checkMultipart(DispatcherServlet.java:1104)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:936)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:661)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
原因
Spring boot项目在导入文件时，没有找到指定文件夹。
子所以是偶发的问题，是因为spring boot项目本身在启动后会自动在Temp文件夹中创建若干临时文件夹，而操作系统可能会定期删除这些临时文件夹。linux也有类似操作系统自动清空临时文件夹的操作，参见这篇文章CentOS7的/tmp目录自动清理规则。