Managing Object Metadata

Scenarios

Object metadata is a set of name-value pairs that describe the object, and are used for object management.

Currently, only the metadata defined by the system is supported.

The metadata defined by the system is classified into the following types: system-controlled and user-controlled. For example, metadata such as Last-Modified is controlled by the system and cannot be modified. You can modify the metadata such as ContentLanguage through the API. The metadata that can be modified is described as follows:

**Table 1** OBS metadata
Name	Description
ContentDisposition	Provides a default file name for the object that is being requested. When an object is being downloaded or accessed, the file with the default file name is directly displayed in the browser or a download dialog box is displayed if the file is being accessed. For example, select ContentDisposition as the metadata name and enter attachment;filename="testfile.xls" as the metadata value for an object. If you access the object through a link, a dialog box is directly displayed for downloading objects, and the object name is changed to testfile.xls. For details, see the definition about ContentDisposition in HTTP.
ContentLanguage	Indicates the language or languages intended for the audience. Therefore, a user can differentiate according to the user's preferred language. For details, see the definition about ContentLanguage in HTTP.
WebsiteRedirectLocation	Redirects an object to another object or an external URL. The redirection function is implemented using static website hosting. For example, you can perform the following operations to implement object redirection: Set metadata of object testobject.html in the root directory of bucket testbucket. Select WebsiteRedirectLocation for Name and enter http://www.example.com for Value. NOTE: OBS only supports redirection for objects in the root directory of a bucket. Configure static website hosting for bucket testbucket, and set the object testobject.html in the bucket as the default home page of the hosted static website. If you access object testobject.html through the URL link provided on the Configure Static Website Hosting page, the access request is redirected to http://www.example.com.
ContentEncoding	Content encoding format when an object is downloaded. The options are as follows: Standard: compress, deflate, exi, identity, gzip, and pack200-gzip Others: br, bzip2, lzma, peerdist, sdch, xpress, and xz
CacheControl	Cache behavior of the web page when the specified object is downloaded. Cacheability: public, private, no-cache, and only-if-cached Expiration time: *max-age=<seconds*>, s-maxage=<seconds>, max-stale[=<seconds>], min-fresh=<seconds>, stale-while-revalidate=<seconds>, stale-if-error=<seconds> Re-verification and reloading: must-revalidate, proxy-revalidate, and immutable Others: no-store and no-transform**
Expires	Cache expiration time (GMT)
ContentType	File type of an object. For details, see Object Metadata Content-Type.

When versioning is enabled for a bucket, you can set metadata for objects which are Latest Version, but cannot set metadata for objects which are Historical Version.
You cannot configure object metadata for an Archive object.

Object Metadata Content-Type

When an object is uploaded to OBS through OBS Console or a tool, the system automatically matches the value of Content-Type based on the file name extension of the object. When you access an object through a web browser, the system specifies an application to open the object according to the value of Content-Type. You can modify the Content-Type of an object based on its file name extension.

If you upload an object by calling an API, specify the value of Content-Type because the system does not automatically match the value of Content-Type.

**Table 2** Common Content-Type values
File Name Extension	Content-Type	File Name Extension	Content-Type
.* (binary stream, unknown file type)	application/octet-stream	.7z	application/x-7z-compressed
.001	application/x-001	.301	application/x-301
.323	text/h323	.906	application/x-906
.907	drawing/907	.a11	application/x-a11
.acp	audio/x-mei-aac	.ai	application/postscript
.aif	audio/aiff	.aifc	audio/aiff
.aiff	audio/aiff	.anv	application/x-anv
.asa	text/asa	.asf	video/x-ms-asf
.asp	text/asp	.asx	video/x-ms-asf
.au	audio/basic	.avi	video/avi
.awf	application/vnd.adobe.workflow	.biz	text/xml
.bmp	application/x-bmp	.bot	application/x-bot
.c4t	application/x-c4t	.c90	application/x-c90
.cal	application/x-cals	.cat	application/vnd.ms-pki.seccat
.cdf	application/x-netcdf	.cdr	application/x-cdr
.cel	application/x-cel	.cer	application/x-x509-ca-cert
.cg4	application/x-g4	.cgm	application/x-cgm
.cit	application/x-cit	.class	java/*
.cml	text/xml	.cmp	application/x-cmp
.cmx	application/x-cmx	.cot	application/x-cot
.crl	application/pkix-crl	.crt	application/x-x509-ca-cert
.csi	application/x-csi	.css	text/css
.cut	application/x-cut	.dbf	application/x-dbf
.dbm	application/x-dbm	.dbx	application/x-dbx
.dcd	text/xml	.dcx	application/x-dcx
.der	application/x-x509-ca-cert	.dgn	application/x-dgn
.dib	application/x-dib	.dll	application/x-msdownload
.doc	application/msword	.docx	application/vnd.openxmlformats-officedocument.wordprocessingml.document
.drw	application/x-drw	.dot	application/msword
.dwf	Model/vnd.dwf	.dtd	text/xml
.dwg	application/x-dwg	.dwf	application/x-dwf
.dxf	application/x-dxf	.dxb	application/x-dxb
.emf	application/x-emf	.edn	application/vnd.adobe.edn
.ent	text/xml	.eml	message/rfc822
.eps	application/x-ps	.epi	application/x-epi
.etd	application/x-ebx	.eps	application/postscript
.fax	image/fax	.exe	application/x-msdownload
.fif	application/fractals	.fdf	application/vnd.fdf
.frm	application/x-frm	.fo	text/xml
.gbr	application/x-gbr	.g4	application/x-g4
.gif	image/gif	.	application/x-
.gp4	application/x-gp4	.gl2	application/x-gl2
.hmr	application/x-hmr	.hgl	application/x-hgl
.hpl	application/x-hpl	.hpg	application/x-hpgl
.hrf	application/x-hrf	.hqx	application/mac-binhex40
.htc	text/x-component	.hta	application/hta
.html	text/html	.htm	text/html
.htx	text/html	.htt	text/webviewhtml
.ico	image/x-icon	.icb	application/x-icb
.iff	application/x-iff	.ico	application/x-ico
.igs	application/x-igs	.ig4	application/x-g4
.img	application/x-img	.iii	application/x-iphone
.isp	application/x-internet-signup	.ins	application/x-internet-signup
.java	java/*	.IVF	video/x-ivf
.jpe	image/jpeg	.jfif	image/jpeg
.jpeg	image/jpeg	.jpe	application/x-jpe
.jpg	application/x-jpg	.jpg	image/jpeg
.jsp	text/html	.js	text/javascript
.lar	application/x-laplayer-reg	.la1	audio/x-liquid-file
.lavs	audio/x-liquid-secure	.latex	application/x-latex
.lmsff	audio/x-la-lms	.lbm	application/x-lbm
.ltr	application/x-ltr	.ls	application/x-javascript
.m2v	video/x-mpeg	.m1v	video/x-mpeg
.m4e	video/mpeg4	.m3u	audio/mpegurl
.man	application/x-troff-man	.mac	application/x-mac
.mdb	application/msaccess	.math	text/xml
.mfp	application/x-shockwave-flash	.mdb	application/x-mdb
.mhtml	message/rfc822	.mht	message/rfc822
.mid	audio/mid	.mi	application/x-mi
.mil	application/x-mil	.midi	audio/mid
.mnd	audio/x-musicnet-download	.mml	text/xml
.mocha	application/x-javascript	.mns	audio/x-musicnet-stream
.mp1	audio/mp1	.movie	video/x-sgi-movie
.mp2v	video/mpeg	.mp2	audio/mp2
.mp4	video/mp4	.mp3	audio/mp3
.mpd	application/vnd.ms-project	.mpa	video/x-mpg
.mpeg	video/mpg	.mpe	video/x-mpeg
.mpga	audio/rn-mpeg	.mpg	video/mpg
.mps	video/x-mpeg	.mpp	application/vnd.ms-project
.mpv	video/mpg	.mpt	application/vnd.ms-project
.mpw	application/vnd.ms-project	.mpv2	video/mpeg
.mtx	text/xml	.mpx	application/vnd.ms-project
.net	image/pnetvue	.mxp	application/x-mmxp
.nws	message/rfc822	.nrf	application/x-nrf
.out	application/x-out	.odc	text/x-ms-odc
.p12	application/x-pkcs12	.p10	application/pkcs10
.p7c	application/pkcs7-mime	.p7b	application/x-pkcs7-certificates
.p7r	application/x-pkcs7-certreqresp	.p7m	application/pkcs7-mime
.pc5	application/x-pc5	.p7s	application/pkcs7-signature
.pcl	application/x-pcl	.pci	application/x-pci
.pdf	application/pdf	.pcx	application/x-pcx
.pdx	application/vnd.adobe.pdx	.pfx	application/x-pkcs12
.pgl	application/x-pgl	.pic	application/x-pic
.pko	application/vnd.ms-pki.pko	.pl	application/x-perl
.plg	text/html	.pls	audio/scpls
.plt	application/x-plt	.png	image/png
.png	application/x-png	.pot	application/vnd.ms-powerpoint
.ppa	application/vnd.ms-powerpoint	.ppm	application/x-ppm
.pps	application/vnd.ms-powerpoint	.ppt	application/vnd.ms-powerpoint
.ppt	application/x-ppt	.pr	application/x-pr
.prf	application/pics-rules	.prn	application/x-prn
.prt	application/x-prt	.ps	application/x-ps
.ps	application/postscript	.ptn	application/x-ptn
.pwz	application/vnd.ms-powerpoint	.r3t	text/vnd.rn-realtext3d
.ra	audio/vnd.rn-realaudio	.ram	audio/x-pn-realaudio
.ras	application/x-ras	.rat	application/rat-file
.rdf	text/xml	.rec	application/vnd.rn-recording
.red	application/x-red	.rgb	application/x-rgb
.rjs	application/vnd.rn-realsystem-rjs	.rjt	application/vnd.rn-realsystem-rjt
.rlc	application/x-rlc	.rle	application/x-rle
.rm	application/vnd.rn-realmedia	.rmf	application/vnd.adobe.rmf
.rmi	audio/mid	.rmj	application/vnd.rn-realsystem-rmj
.rmm	audio/x-pn-realaudio	.rmp	application/vnd.rn-rn_music_package
.rms	application/vnd.rn-realmedia-secure	.rmvb	application/vnd.rn-realmedia-vbr
.rmx	application/vnd.rn-realsystem-rmx	.rnx	application/vnd.rn-realplayer
.rp	image/vnd.rn-realpix	.rpm	audio/x-pn-realaudio-plugin
.rsml	application/vnd.rn-rsml	.rt	text/vnd.rn-realtext
.rtf	application/msword	.rtf	application/x-rtf
.rv	video/vnd.rn-realvideo	.sam	application/x-sam
.sat	application/x-sat	.sdp	application/sdp
.sdw	application/x-sdw	.sit	application/x-stuffit
.slb	application/x-slb	.sld	application/x-sld
.slk	drawing/x-slk	.smi	application/smil
.smil	application/smil	.smk	application/x-smk
.snd	audio/basic	.sol	text/plain
.sor	text/plain	.spc	application/x-pkcs7-certificates
.spl	application/futuresplash	.spp	text/xml
.ssm	application/streamingmedia	.sst	application/vnd.ms-pki.certstore
.stl	application/vnd.ms-pki.stl	.stm	text/html
.sty	application/x-sty	.svg	text/svg+xml
.swf	application/x-shockwave-flash	.tdf	application/x-tdf
.tg4	application/x-tg4	.tga	application/x-tga
.tif	image/tiff	.tif	application/x-tif
.tiff	image/tiff	.tld	text/xml
.top	drawing/x-top	.torrent	application/x-bittorrent
.tsd	text/xml	.txt	text/plain
.uin	application/x-icq	.uls	text/iuls
.vcf	text/x-vcard	.vda	application/x-vda
.vdx	application/vnd.visio	.vml	text/xml
.vpg	application/x-vpeg005	.vsd	application/vnd.visio
.vsd	application/x-vsd	.vss	application/vnd.visio
.vst	application/vnd.visio	.vst	application/x-vst
.vsw	application/vnd.visio	.vsx	application/vnd.visio
.vtx	application/vnd.visio	.vxml	text/xml
.wav	audio/wav	.wax	audio/x-ms-wax
.wb1	application/x-wb1	.wb2	application/x-wb2
.wb3	application/x-wb3	.wbmp	image/vnd.wap.wbmp
.wiz	application/msword	.wk3	application/x-wk3
.wk4	application/x-wk4	.wkq	application/x-wkq
.wks	application/x-wks	.wm	video/x-ms-wm
.wma	audio/x-ms-wma	.wmd	application/x-ms-wmd
.wmf	application/x-wmf	.wml	text/vnd.wap.wml
.wmv	video/x-ms-wmv	.wmx	video/x-ms-wmx
.wmz	application/x-ms-wmz	.wp6	application/x-wp6
.wpd	application/x-wpd	.wpg	application/x-wpg
.wpl	application/vnd.ms-wpl	.wq1	application/x-wq1
.wr1	application/x-wr1	.wri	application/x-wri
.wrk	application/x-wrk	.ws	application/x-ws
.ws2	application/x-ws	.wsc	text/scriptlet
.wsdl	text/xml	.wvx	video/x-ms-wvx
.xdp	application/vnd.adobe.xdp	.xdr	text/xml
.xfd	application/vnd.adobe.xfd	.xfdf	application/vnd.adobe.xfdf
.xhtml	text/html	.xls	application/vnd.ms-excel
.xls	application/x-xls	.xlw	application/x-xlw
.xml	text/xml	.xpl	audio/scpls
.xq	text/xml	.xql	text/xml
.xquery	text/xml	.xsd	text/xml
.xsl	text/xml	.xslt	text/xml
.xwd	application/x-xwd	.x_b	application/x-x_b
.sis	application/vnd.symbian.install	.sisx	application/vnd.symbian.install
.x_t	application/x-x_t	.ipa	application/vnd.iphone
.apk	application/vnd.android.package-archive	.xap	application/x-silverlight-app
.zip	application/zip	.rar	application/x-rar-compressed

User-Defined Object Metadata

You can add the user-defined metadata whose name starts with x-obs-meta- for easy object management. When you retrieve or query the metadata of the object, the added user-defined metadata will be returned in the response header. The user-defined metadata is limited to 8 KB in size. To measure the total size of user-defined metadata, sum the number of bytes in the UTF-8 encoding of each key and value.

The user-defined metadata keys are case insensitive, but are stored in lowercase by OBS. The key values are case sensitive.

The following is an example.

    
         PUT /key HTTP/1.1
Host: bucket01.obs.myhuaweicloud.com
x-obs-meta-Test1: Test Meta1

HEAD /Key HTTP/1.1
Host: bucket01.obs.myhuaweicloud.com
x-obs-meta-test1: Test Meta1

Both user-defined metadata keys and their values must conform to US-ASCII standards. If non-ASCII or unrecognizable characters are necessary, they must be encoded or decoded in URL or Base64 on the client side, because the server side does not perform any decoding.

How to Use

You can use OBS Console, APIs, SDKs, or obsutil to customize object metadata.

Tool	Reference
OBS Console	Configuring Object Metadata
SDKs	OBS supports software development kits (SDKs) in multiple languages. For details, see the corresponding developer guide on the SDK Overview page.
API	Modifying Object Metadata
obsutil	Uploading an Object