文件格式对应http的Content-Type字段

"doc" = "application/msword"
"bin" = "application/octet-stream"
"dll" = "application/octet-stream"
"exe" = "application/octet-stream"
"pdf" = "application/pdf"
"p7c" = "application/pkcs7-mime"
"ai" = "application/postscript"
"eps" = "application/postscript"
"ps" = "application/postscript"
"rtf" = "application/rtf"
"fdf" = "application/vnd.fdf"
"arj" = "application/x-arj"
"gz" = "application/x-gzip"
"class" = "application/x-java-class"
"js" = "application/x-javascript"
"lzh" = "application/x-lzh"
"lnk" = "application/x-ms-shortcut"
"tar" = "application/x-tar"
"hlp" = "application/x-winhelp"
"cert" = "application/x-x509-ca-cert"
"zip" = "application/zip"
"cab" = "application/x-compressed"
"arj" = "application/x-compressed"
"aif" = "audio/aiff"
"aifc" = "audio/aiff"
"aiff" = "audio/aiff"
"au" = "audio/basic"
"snd" = "audio/basic"
"mid" = "audio/midi"
"rmi" = "audio/midi"
"mp3" = "audio/mpeg"
"vox" = "audio/voxware"
"wav" = "audio/wav"
"ra" = "audio/x-pn-realaudio"
"ram" = "audio/x-pn-realaudio"
"bmp" = "image/bmp"
"gif" = "image/gif"
"jpeg" = "image/jpeg"
"jpg" = "image/jpeg"
"tif" = "image/tiff"
"tiff" = "image/tiff"
"xbm" = "image/xbm"
"wrl" = "model/vrml"
"htm" = "text/html"
"html" = "text/html"
"c" = "text/plain"
"cpp" = "text/plain"
"def" = "text/plain"
"h" = "text/plain"
"txt" = "text/plain"
"rtx" = "text/richtext"
"rtf" = "text/richtext"
"java" = "text/x-java-source"
"css" = "text/css"
"mpeg" = "video/mpeg"
"mpg" = "video/mpeg"
"mpe" = "video/mpeg"
"avi" = "video/msvideo"
"mov" = "video/quicktime"
"qt" = "video/quicktime"
"shtml" = "wwwserver/html-ssi"
"asa" = "wwwserver/isapi"
"asp" = "wwwserver/isapi"
"cfm" = "wwwserver/isapi"
"dbm" = "wwwserver/isapi"
"isa" = "wwwserver/isapi"
"plx" = "wwwserver/isapi"
"url" = "wwwserver/isapi"
"cgi" = "wwwserver/isapi"
"php" = "wwwserver/isapi"
"wcgi" = "wwwserver/isapi"