Language and File Types Oracle Application Server Tips by Burleson Consulting

The next section of the httpd.conf file deals with file types or mime support.  Again, this section is inside a Block Directive, and will only be read if the test returns true.  Mime support provides metadata about files, so that OHS can service requests correctly, or if necessary, pass that information to the client so that they can handle the file correctly.  We saw this in action with the MultiViews option above. A good example is language support. 

OHS uses the module mod_negotiation to select the correct file using file mappings, or by executing a filename pattern match and choosing from the results.  Files used by OHS to service requests can have multiple extensions. The order of the extension does not matter unless OHS cannot identify an extension.  In that case, OHS uses the extensions to the right of the unidentified extension only.  For example:

filename.jwg.html.en
filename.jwg.en.html
filename.en.jwg.html

In the three files above, we have defined types for html and en, but not for jwg.  The first two files are identified as an HTML file associated with the language English.  The last file is only identified as an HTML file and no language information can be determined.  So, the order file extensions added are irrelevant, as long as the undefined extensions are to the left of the defined extensions.  Also, extensions are case sensitive (.z and .Z are two different extensions).  Lets return to our httpd.conf file and walk through this section.

<IfModule mod_mime.c>
    TypesConfig /home/oracle/oraportal904/Apache/Apache/conf/mime.types
    AddEncoding x-compress Z
    AddEncoding x-gzip gz tgz

The fist step is to read a file that is used to define a long list of file types called mime.types.  Next, it defines additional extensions for compressed files.   This mapping is added to existing mapping and will override any mappings that already exist for these extensions.  The above example marks a file with the .Z extension as encoded using x-compress, and any file with the .gz or .tgz as encoded using x-gzip.

Now lets look at the language types and character sets.  When a client browser initiates a request, it supplies a heading that also identifies the preferred language.  The preferred language is used to determine which file to serve that browser if there are a number of files to select from.  Taking another section from the httpd.conf file:

    AddLanguage da .da
    AddLanguage nl .nl
    AddLanguage en .en
    AddLanguage et .ee
    AddLanguage fr .fr
    AddLanguage de .de
    AddLanguage el .el
    AddLanguage es .es_ES
    AddLanguage he .he
    AddCharset ISO-8859-8 .iso8859-8
    AddLanguage it .it
    AddLanguage ja .ja
    AddCharset ISO-2022-JP .jis
    AddLanguage ko .ko
    AddLanguage kr .kr
    AddCharset ISO-2022-KR .iso-kr
    AddLanguage no .no
    AddLanguage pl .po
    AddCharset ISO-8859-2 .iso-pl
    AddLanguage pt .pt
    AddLanguage pt-br .pt-br
    AddLanguage pt-BR .pt_BR

In this section we define file extensions that support different languages.  Using the AddLanguage directive allows you to map an extension to a language code.  Normally, the extension is the same as the language code, however, some will differ. 

The language code for Poland is pl, however, the .pl extension usually denotes a Perl script.  Thus, we can map .po to the language code pl and use the .po extension on the Polish documents.

Another thing to note is that documents in some languages need a specific character set to properly display.  This can be defined using the AddCharset directive.  For example, the Korean language code is kr. We can see above that it maps to the .kr extension.  However, for the browser to properly display this document, it needs to also know which character set to use.  The character set ISO-2022-KR is mapped to the extension .iso-kr.  Thus, a document in the format  filename.html.iso-kr.kr is an html document that requires the ISO-2022-KR character set and is in Korean. 

It is important to note that an extension can only be mapped to one language.  In the code segment below, .en is mapped only to kr while both .po and .pl are mapped to Polish.

    AddLanguage en .en
    AddLanguage pl .pl
    AddLanguage pl .po
    AddLanguage kr .en
     

If more than one mapping is present for a single extension, the last occurrence is used.  The final step in defining language support is to provide a priority list, so that if two files tie, OHS will know which to use.

<IfModule mod_negotiation.c>
    LanguagePriority en da nl et de el it ja kr no pl pt pt-br ru
</IfModule>

This nested Block Directive establishes a priority list in descending order to be used by the module mod_negotiation to break a tie.  Note that it is a language list, not an extensions list.

The final directive dealing with file types is the location of the magic file.  This file is used by the module mod_mime_magic and is normally located in the ServerRoot/conf directory.  This module will look into an unknown file and use the definitions in the magic file to try and determine the file type.

 

This is an excerpt from "Oracle 10g Application Server Administration Handbook" by Don Burleson and John Garmany.