express-negotiator
v1.1.0
Published
Express/connect middleware that does HTTP content negotiation for static files
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express-negotiator
Express/connect middleware for doing content negotiation with static files on disc. Heavily inspired by Apache's mod_negotiation.
Negotiator rewrites req.url
to the negotiated file name based on
these factors (in descending order of importance):
- Whether
req.url
matches a file name on disc exactly - The
locale
GET parameter - The value of a locale cookie (optional, specified by
options.cookieName
) - The
Accept-Language
andAccept
headers
... and of course the availability of suitable files on disc. If no
acceptable match is found, req.url
is left untouched.
Like mod_negotiation
, express-negotiator
interprets the extensions
of the files on disc as an unordered set. A file called foo.html.fr
would be treated the same as one called foo.fr.html
except when the
request url specifies an exact match.
The negotiator middleware is intended to run right before static
pointed at the same directory as options.root
.
If options.cookieName
is specified, the cookieParser
middleware
must also be in the middleware chain.
Conditional requests
When the url is rewritten, negotiator sets the ETag header to the same
value as the static
middleware would
("<size>-<modificationTime>"
), but with the negotiated Content-Type
and locale id bits suffixed. This prevents false positive 304
responses with If-None-Match
when the same client (or reverse proxy)
requests the same url later with different headers (eg. after a locale
cookie change). That would happen if the files happened to have the
same size and modification times.
Also, the If-Modified-Since
header is removed since that would cause
the static
middleware to reply 304 Not Modified
in similar
situations. ETags are a superior concept anyway.
Installation
Make sure you have node.js and npm installed, then run:
$ npm install express-negotiator
Example usage
var express = require('express'),
negotiator = require('express-negotiator'),
root = '/path/to/static/files',
app = express.createServer();
app
.use(express.cookieParser())
.use(negotiator({root: root, cookieName: 'mycookie'}))
.use(express.static(root))
.listen(1337);
If the root dir contains the files index.en.html
, index.da.html
,
and foo.png
these example requests would be rewritten as follows:
GET / HTTP/1.1
Accept: text/html
Accept-Language: en
=> /index.en.html
Response ETag: "<size>-<modificationTime>-text/html-en"
GET /?locale=da HTTP/1.1
Accept: text/html
Accept-Language: en
=> /index.da.html
Response ETag: "<size>-<modificationTime>-text/html-da"
GET /index HTTP/1.1
Cookie: mycookie=da
Accept: text/html
Accept-Language: en
=> /index.da.html
Response ETag: "<size>-<modificationTime>-text/html-da"
GET /foo HTTP/1.1
Accept: image/*
=> /foo.png
Response ETag: "<size>-<modificationTime>-image/png"
See the test suite for more examples.
License
express-negotiator is licensed under a standard 3-clause BSD license
-- see the LICENSE
file for details.