http中的Content-Type
要学习content-type,必须事先知道它到底是什么,是干什么用的。
HTTP协议(RFC2616)采用了请求/响应模型。客户端向服务器发送一个请求,请求头包含请求的方法、URI、协议版本、以及包含请求修饰符、客户 信息和内容的类似于MIME的消息结构。服务器以一个状态行作为响应,相应的内容包括消息协议的版本,成功或者错误编码加上包含服务器信息、实体元信息以 及可能的实体内容。
通常HTTP消息由一个起始行,一个或者多个头域,一个只是头域结束的空行和可选的消息体组成。HTTP的头域包括通用头,请求头,响应头和实体头四个部 分。每个头域由一个域名,冒号(:)和域值三部分组成。域名是大小写无关的,域 值前可以添加任何数量的空格符,头域可以被扩展为多行,在每行开始处,使用至少一个空格或制表符。
请求消息和响应消息都可以包含实体信息,实体信息一般由实体头域和实体组成。实体头域包含关于实体的原信息,实体头包括Allow、Content- Base、Content-Encoding、Content-Language、 Content-Length、Content-Location、Content-MD5、Content-Range、Content-Type、 Etag、Expires、Last-Modified、extension-header。
Content-Type是返回消息中非常重要的内容,表示后面的文档属于什么MIME类型。Content-Type: [type]/[subtype]; parameter。例如最常见的就是text/html,它的意思是说返回的内容是文本类型,这个文本又是HTML格式的。原则上浏览器会根据Content-Type来决定如何显示返回的消息体内容。
type有下面的形式。
Text:用于标准化地表示的文本信息,文本消息可以是多种字符集和或者多种格式的;
Multipart:用于连接消息体的多个部分构成一个消息,这些部分可以是不同类型的数据;
Application:用于传输应用程序数据或者二进制数据;
Message:用于包装一个E-mail消息;
Image:用于传输静态图片数据;
Audio:用于传输音频或者音声数据;
Video:用于传输动态影像数据,可以是与音频编辑在一起的视频数据格式。
subtype用于指定type的详细形式。content-type/subtype配对的集合和与此相关的参数,将随着时间而增长。为了确保这些值在一个有序而且公开的状态下开发,MIME使用Internet Assigned Numbers Authority (IANA)作为中心的注册机制来管理这些值。
parameter可以用来指定附加的信息,更多情况下是用于指定text/plain和text/htm等的文字编码方式的charset参数。MIME根据type制定了默认的subtype,当客户端不能确定消息的subtype的情况下,消息被看作默认的subtype进行处理。Text默认是text/plain,Application默认是application/octet-stream而Multipart默认情况下被看作multipart/mixed。
MIME定义在RFC-2046 MIME Part 2: Media Types 。
常用类型:
Mime Types By File Extension
Extension |
Type/sub-type |
|
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 |
|
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 |
对于IE6浏览器来说,如果Content-Type中的类型和实际的消息体类型不一致,那么它会根据内容中的类型来分析实际应该是什么类型,对于JPG、GIF等常用图片格式都可以正确的识别出来,而不管Content-Type中写的是什么。
如果Content-Type中指定的是浏览器可以直接打开的类型,那么浏览器就会直接打开其内容显示出来,如果是被关联到其它应用程序的类型,这时就要
查找注册表中关于这种类型的注册情况,如果是允许直接打开而不需要询问的,就会直接调出这个关联的应用程序来打开这个文件,但如果是不允许直接打开的,就
会询问是否打开。对于没有关联到任何应用程序的类型,IE浏览器不知道它该如何打开,此时IE6就会把它当成XML来尝试打开。
如果要想实现文件下载,可以在http的头中加入:
fprintf( file, "Content-Disposition:attachment; filename=\"%s\" \r\n", fileName);
经过测试,html,pdf,gif等原来在网页中打开的文件都可以正常实现下载。
努力把老板的双手搞残废,我顶替他的双手。