我使用的是poi 3.7，上传的文件是.xlsx

控制台显示：

org.apache.poi.POIXMLException: org.apache.poi.openxml4j.exceptions.InvalidFormatException: Package should contain a content type part [M1.13]
    at org.apache.poi.util.PackageHelper.open(PackageHelper.java:41)
    at org.apache.poi.xssf.usermodel.XSSFWorkbook.<init>(XSSFWorkbook.java:186)
    at poi.POITest.ReadAndPrintExcelFile(POITest.java:15)
    at poi.POITest.main(POITest.java:59)
Caused by: org.apache.poi.openxml4j.exceptions.InvalidFormatException: Package should contain a content type part [M1.13]
    at org.apache.poi.openxml4j.opc.ZipPackage.getPartsImpl(ZipPackage.java:147)
    at org.apache.poi.openxml4j.opc.OPCPackage.getParts(OPCPackage.java:592)
    at org.apache.poi.openxml4j.opc.OPCPackage.open(OPCPackage.java:222)
    at org.apache.poi.util.PackageHelper.open(PackageHelper.java:39)
    ... 3 more