 | Apache: The Definitive Guide |  |
In the last section, we looked at multiviews as a way of providing language and image negotiation. The other way to achieve the same effects in the current release of Apache, and more lavish effects later (probably to negotiate browser plug-ins), is to use type maps, also known as *.var files. Multiviews works by scrambling together a vanilla type map; now you have the chance to set it up just as you want it. The Config file is as follows:
User webuser Group webgroup ServerName www.butterthlies.com DocumentRoot /usr/www/site.typemap/htdocs AddHandler type-map var DirectoryIndex index.var AccessConfig /dev/null ResourceConfig /dev/null
One should write, as seen in this file:
AddHandler type-map var
Having set that, we can sensibly say:
DirectoryIndex index.var
to set up a set of language-specific indexes.
What this means, in plainer English, is that the DirectoryIndex line overrides the default index file index.html. If you also want index.html to be used as an alternative, you would have to specify it -- but you probably don't, because you are trying to do something more elaborate here. In this case there are several versions of the index: index.en.html, index.it.html, index.ko.html, so Apache looks for index.var for an explanation.
Look at ... /site.typemap/htdocs. We want to offer language-specific versions of the index.html file and alternatives to the generalized images bath, hen, tree, and bench, so we create two files, index.var and bench.var (we will only bother with one of the images, since the others are the same).
This is index.var :
# It seems that this URI _must_ be the filename minus the extension... URI: index; vary="language" URI: index.en.html # Seems we _must_ have the Content-type or it doesn't work... Content-type: text/html Content-language: en URI: index.it.html Content-type: text/html Content-language: it
This is bench.var :
URI: bench; vary="type" URI: bench.jpg Content-type: image/jpeg; qs=0.8 level=3 URI: bench.gif Content-type: image/gif; qs=0.5 level=1
The first line tells Apache what file is in question, here index.* or bench.* ; vary tells Apache what sort of variation we have. The possibilities are:
type
language
charset
encoding
The name of the corresponding header, as defined in the HTTP specification, is obtained by prefixing these names with Content-. The headers are:
Content-type
Content-language
Content-charset
Content-encoding
The qs numbers are quality scores , from to 1. You decide what they are and write them in. The qs values for each type of return are multiplied to give the overall qs for each variant. For instance, if a variant has a qs of .5 for Content-type and a qs of .7 for Content-language, its overall qs is .35. The higher the result, the better. The level values are also numbers, and you decide what they are. In order for Apache to decide rationally which possibility to return, it resolves ties in the following way:
Find the best (highest) qs.
If there's a tie, count the occurrences of "*" in the type and choose the one with the lowest value (i.e., the one with the least wildcarding).
If there's still a tie, choose the type with the highest language priority.
If there's still a tie, choose the type with the highest level number.
If there's still a tie, choose the highest content length.
If you can predict the outcome of all this in your head, you must qualify for some pretty classy award! Following is the full list of possible directives, given in the Apache documentation:
URI of the file containing the variant (of the given media type, encoded with the given content encoding). These are interpreted as URLs relative to the map file; they must be on the same server (!), and they must refer to files to which the client would be granted access if the files were requested directly.
These are often referred to as MIME types; typical media types are image/gif, text/plain, or text/html.
The language of the variant, specified as an Internet standard language code (e.g., en for English, ko for Korean).
If the file is compressed or otherwise encoded, rather than containing the actual raw data, this value says how compression was done. For compressed files (the only case where this generally comes up), content encoding should be x-compress or gzip, as appropriate.
The size of the file. The size of the file is used by Apache to decide which file to send; specifying a content length in the map allows the server to compare the length without checking the actual file.
To throw this into action, start Apache with ./go, set the language of your browser to Italian, (in Netscape, choose Edit→Preferences→Netscape→Languages) and access http://www.butterthlies.com /. You should see the Italian version.
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| 6.3. Language Negotiation |  | 6.5. Browsers and HTTP/1.1 |
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