java实现浏览器下载文件,并解决兼容各浏览器的乱码与后缀问题

之前用java写了一个文件流输出文件的功能，测试细节功能的时候，发现了许多问题

一、火狐浏览器下载带中文名字的文件会乱码，其他浏览器不会

1、原因：找了下资料后发现，是火狐使用了RFC 2183协议。

文件名存在http header中的filename，Content-Disposition: attachment; filename=FILENAME，该filename参数可用于为浏览器下载资源的文件的名称提供建议。但是，RFC 2183中声明文件名只能使用US-ASCII字符，目前大多数流行的Web浏览器似乎允许非US-ASCII字符（由于缺乏标准）在编码方案和文件名的字符集规范上不同意。那么问题是，如果文件名“naïvefile”（没有引号和第三个字母是U + 00EF）需要编码到Content-Disposition头文件中。 

2、解决方案：因此只需要在Content-Disposition做下处理即可：重点是filename*=utf-8'zh_cn'

byte[] source = (byte[]) result.get("exportData");
HttpServletResponse response = RequestContextHolder.getRequestAttributes().getResponse();
if (response != null) {
    response.reset();
    response.setHeader("Content-Disposition", "attachment;filename*=utf-8'zh_cn'" + URLEncoder.encode("导出文件名.csv", "UTF-8"));
    response.setHeader("Connection", "close");
    response.setHeader("Content-Type", "application/octet-stream");
    OutputStream out = response.getOutputStream();
    out.write(source);
    out.flush();
    out.close();
}
           

二、ios系统safiri浏览器导出任何类型文件都变成dms后缀类型的文件

原因：header请求中，Content-Type设置application/octet-stream，而该type类型对应Mime 类型列表刚好是dms后缀的文件，所以safiri浏览器就直接将该文件生成为dms后缀的文件了

解决方案：大部分浏览器都可以使用通用类型application/octet-stream，但遇到特殊的如safiri，就最好是生成什么类型的文件，就传对应的tpye

//这里Content-Type传对应的文件类型，参考下面的MIME表
response.setHeader("Content-Type", "text/csv");
           

另附上Mime 类型列表：

扩展名	类型/子类型
application/octet-stream
323	text/h323
acx	application/internet-property-stream
ai	application/postscript
aif	audio/x-aiff
aifc	audio/x-aiff
aiff	audio/x-aiff
asf	video/x-ms-asf
asr	video/x-ms-asf
asx	video/x-ms-asf
au	audio/basic
avi	video/x-msvideo
axs	application/olescript
bas	text/plain
bcpio	application/x-bcpio
bin	application/octet-stream
bmp	image/bmp
c	text/plain
cat	application/vnd.ms-pkiseccat
cdf	application/x-cdf
cer	application/x-x509-ca-cert
class	application/octet-stream
clp	application/x-msclip
cmx	image/x-cmx
cod	image/cis-cod
cpio	application/x-cpio
crd	application/x-mscardfile
crl	application/pkix-crl
crt	application/x-x509-ca-cert
csh	application/x-csh
css	text/css
dcr	application/x-director
der	application/x-x509-ca-cert
dir	application/x-director
dll	application/x-msdownload
dms	application/octet-stream
doc	application/msword
dot	application/msword
dvi	application/x-dvi
dxr	application/x-director
eps	application/postscript
etx	text/x-setext
evy	application/envoy
exe	application/octet-stream
fif	application/fractals
flr	x-world/x-vrml
gif	image/gif
gtar	application/x-gtar
gz	application/x-gzip
h	text/plain
hdf	application/x-hdf
hlp	application/winhlp
hqx	application/mac-binhex40
hta	application/hta
htc	text/x-component
htm	text/html
html	text/html
htt	text/webviewhtml
ico	image/x-icon
ief	image/ief
iii	application/x-iphone
ins	application/x-internet-signup
isp	application/x-internet-signup
jfif	image/pipeg
jpe	image/jpeg
jpeg	image/jpeg
jpg	image/jpeg
js	application/x-javascript
latex	application/x-latex
lha	application/octet-stream
lsf	video/x-la-asf
lsx	video/x-la-asf
lzh	application/octet-stream
m13	application/x-msmediaview
m14	application/x-msmediaview
m3u	audio/x-mpegurl
man	application/x-troff-man
mdb	application/x-msaccess
me	application/x-troff-me
mht	message/rfc822
mhtml	message/rfc822
mid	audio/mid
mny	application/x-msmoney
mov	video/quicktime
movie	video/x-sgi-movie
mp2	video/mpeg
mp3	audio/mpeg
mpa	video/mpeg
mpe	video/mpeg
mpeg	video/mpeg
mpg	video/mpeg
mpp	application/vnd.ms-project
mpv2	video/mpeg
ms	application/x-troff-ms
mvb	application/x-msmediaview
nws	message/rfc822
oda	application/oda
p10	application/pkcs10
p12	application/x-pkcs12
p7b	application/x-pkcs7-certificates
p7c	application/x-pkcs7-mime
p7m	application/x-pkcs7-mime
p7r	application/x-pkcs7-certreqresp
p7s	application/x-pkcs7-signature
pbm	image/x-portable-bitmap
pdf	application/pdf
pfx	application/x-pkcs12
pgm	image/x-portable-graymap
pko	application/ynd.ms-pkipko
pma	application/x-perfmon
pmc	application/x-perfmon
pml	application/x-perfmon
pmr	application/x-perfmon
pmw	application/x-perfmon
pnm	image/x-portable-anymap
pot,	application/vnd.ms-powerpoint
ppm	image/x-portable-pixmap
pps	application/vnd.ms-powerpoint
ppt	application/vnd.ms-powerpoint
prf	application/pics-rules
ps	application/postscript
pub	application/x-mspublisher
qt	video/quicktime
ra	audio/x-pn-realaudio
ram	audio/x-pn-realaudio
ras	image/x-cmu-raster
rgb	image/x-rgb
rmi	audio/mid
roff	application/x-troff
rtf	application/rtf
rtx	text/richtext
scd	application/x-msschedule
sct	text/scriptlet
setpay	application/set-payment-initiation
setreg	application/set-registration-initiation
sh	application/x-sh
shar	application/x-shar
sit	application/x-stuffit
snd	audio/basic
spc	application/x-pkcs7-certificates
spl	application/futuresplash
src	application/x-wais-source
sst	application/vnd.ms-pkicertstore
stl	application/vnd.ms-pkistl
stm	text/html
svg	image/svg+xml
sv4cpio	application/x-sv4cpio
sv4crc	application/x-sv4crc
swf	application/x-shockwave-flash
t	application/x-troff
tar	application/x-tar
tcl	application/x-tcl
tex	application/x-tex
texi	application/x-texinfo
texinfo	application/x-texinfo
tgz	application/x-compressed
tif	image/tiff
tiff	image/tiff
tr	application/x-troff
trm	application/x-msterminal
tsv	text/tab-separated-values
txt	text/plain
uls	text/iuls
ustar	application/x-ustar
vcf	text/x-vcard
vrml	x-world/x-vrml
wav	audio/x-wav
wcm	application/vnd.ms-works
wdb	application/vnd.ms-works
wks	application/vnd.ms-works
wmf	application/x-msmetafile
wps	application/vnd.ms-works
wri	application/x-mswrite
wrl	x-world/x-vrml
wrz	x-world/x-vrml
xaf	x-world/x-vrml
xbm	image/x-xbitmap
xla	application/vnd.ms-excel
xlc	application/vnd.ms-excel
xlm	application/vnd.ms-excel
xls	application/vnd.ms-excel
xlt	application/vnd.ms-excel
xlw	application/vnd.ms-excel
xof	x-world/x-vrml
xpm	image/x-xpixmap
xwd	image/x-xwindowdump
z	application/x-compress
zip	application/zip
csv	text/csv

三、用GBK编码还是UTF-8？

上面的问题其实还有一个原因，就是中文系统默认编码是GBK的，所以当时生成文件流的时候设置了GBK，但导出的时候却用了UTF-8，所以乱码了。必须使用统一的编码。

ByteArrayOutputStream baos = new ByteArrayOutputStream();
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(baos, "GBK"))
...
byte[] source = baos.toByteArray();
baos.close();
return source;

byte[] source = (byte[]) result.get("exportData");
HttpServletResponse response = DataUtils.getResponse();
if (response != null) {
    response.reset();
    //这里设置了utf-8，不一致
    response.setHeader("Content-Disposition", "attachment;filename*=utf-8'zh_cn'"
                        + URLEncoder.encode(result.get("subject") + ".csv", "UTF-8").replace("+", "%20"));
    response.setHeader("Connection", "close");
    response.setHeader("Content-Type", "text/csv");
    OutputStream out = response.getOutputStream();
    out.write(source);
    out.flush();
    out.close();
}
           

·1、解析：

GBK是在国家标准GB2312基础上扩容后兼容GB2312的标准（好像还不是国家标准）。GBK编码专门用来解决中文编码的，是双字节的。不论中英文都是双字节的。

UTF－8 编码是用以解决国际上字符的一种多字节编码，它对英文使用8位（即一个字节），中文使用24位（三个字节）来编码。对于英文字符较多的论坛则用UTF－8 节省空间。另外，如果是外国人访问你的GBK网页，需要下载中文语言包支持。访问UTF-8编码的网页则不出现这问题。可以直接访问。

GBK包含全部中文字符；UTF-8则包含全世界所有国家需要用到的字符。

经常有人问网页编写UTF-8和GBK哪个编码好，根据个人需要，如果你主要做中文程序的开发，客户也主要是中国人的话就用GBK吧，因为UTF-8编码的中文使用了三个字节，用GBK节省了空间。

如果做英文网站开发，还是用utf-8吧，因为utf-8中英文只占一个字节。GBK中英文也是两个字节的，并且国外客户访问GBK要下载语言包。

如果你的网站是中文的，但国外用户也不少，最好也用UTF-8的吧。

UTF-8编码的文字可以在各国各种支持UTF8字符集的浏览器上显示。

比如，如果是UTF8编码，则在外国人的英文IE上也能显示中文，而无需他们下载IE的中文语言支持包。 所以，对于英文比较多的论坛 ，使用GBK则每个字符占用2个字节，而使用UTF－8英文却只占一个字节。

UTF8是国际编码，它的通用性比较好，外国人也可以浏览论坛，GBK是国家编码，通用性比UTF8差，不过UTF8占用的数据库比GBK大。