Servlet.service() for servlet [servlets.Upload] in context with path [/Excel] threw exception [Servlet execution threw an exception] with root cause java.lang.ClassNotFoundException: org.apache.poi.xssf.usermodel.XSSFWorkbook
在main函数里面和web里面不太一样
web要到web-info底下的lib目录查找 jar
原文：http://www.cnblogs.com/niuni-623/p/6718676.html