在項目中，一般會將文件臨時保存到緩存目錄，當時使用

File.createTempFile("tmp", ext, (File) request.getServletContext().getAttribute(ServletContext.TEMPDIR))

創建臨時文件時，項目一直運行正常，然而有一次報異常：

    The temporary upload location [/tmp/tomcat.7104877156386249310.8070/work/Tomcat/localhost/ROOT] is not valid

檢查文件目錄，文件確實不在，檢查代碼，也未發現問題。實在不知道原因，只有重啟了服務器，問題也就不再出現。

今天偶然查看官方文檔，發現問題所在，也提供了解決方法

If you choose to use Tomcat on CentOS be aware that, by default, a temporary directory is used to store compiled JSPs, file uploads etc. This directory may be deleted by tmpwatch while your application is running leading to failures. To avoid this, you may want to customize your tmpwatch configuration so that tomcat.* directories are not deleted, or configure server.tomcat.basedir so that embedded Tomcat uses a different location

前往目錄/etc/cron.daily/中，修改 tmpwatch文件：

#! /bin/sh
flags=-umc
/usr/sbin/tmpwatch "$flags" -x /tmp/.X11-unix -x /tmp/.XIM-unix \
        -x /tmp/.font-unix -x /tmp/.ICE-unix -x /tmp/.Test-unix \
        -X '/tmp/hsperfdata_*' 10d /tmp \
        -X '/tmp/tomcat.*' 10d /tmp
/usr/sbin/tmpwatch "$flags" 30d /var/tmp
for d in /var/{cache/man,catman}/{cat?,X11R6/cat?,local/cat?}; do
    if [ -d "$d" ]; then
        /usr/sbin/tmpwatch "$flags" -f 30d "$d"
    fi
done

可以看到添加了一行

-X '/tmp/tomcat.*' 10d /tmp