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-----Message d'origine-------
De : web400-bounces@xxxxxxxxxxxx
[mailto:web400-bounces@xxxxxxxxxxxx] De la part de Scott Klement
Envoyà : jeudi 4 juin 2009 18:57
à : Web Enabling the AS400 / iSeries
Objet : Re: [WEB400] Basic CGIDEV2 problem
Hi David,
ScriptAliasMatch lines, though.
I wish I fully understood all those Alias and
Alias, AliasMatch, ScriptAlias and ScriptAliasMatch aren't
too hard to understand. I'll try to explain them, but please
ask questions if you still don't understand.
BACKGROUND
----------
When you configure Apache, you give it a DocumentRoot. This
is an IFS pathname to the start of your web server. In the
simplest configuration, everything on your server would be
under DocumentRoot.
So you might have this:
DocumentRoot /www/myserver/htdocs
HTTP was designed for fetching documents (originally, that's
all you could do, just fetch a document, nothing else). So a
browser would code something like this:
http://www.example.com/mydir/mydoc.html
This tells the browser (a) use the http protocol. (b),
connect to www.example.com, and (c) ask for the document
named /mydir/mydoc.html
Apache will get that request, but it'll add the DocumentRoot
to it. So the actual IFS path to the document will be
/www/myserver/htdocs/mydir/mydoc.html
That's the simplest behavior. It lets you designate some
part of your IFS (DocumentRoot) where all subfolders will be
accessible via URLs.
That's the basic configuration.
ALIAS
-----
What if you want something OUTSIDE of that area to be
accessible to the browser? How would you do it? You declare
an Alias.
DocumentRoot /www/myserver/htdocs
Alias /foo /home/scott/bar
This says that all URLs go under /www/myserver/htdocs, just
as in the previous example... EXCEPT for /foo. Any URL
starting with /foo will point to /home/scott/bar
So this works just as it did before:
http://www.example.com/mydir/mydoc.html
But this works differently.
http://www.example.com/foo/mydir/mydoc.html
In this second case, the /foo is an alias for
/home/scott/foo, so the URL points to
/home/scott/bar/mydir/mydoc.html.
That's all an alias does. It provides a way to specify
directories in the URL that are "redirected" to another area
of the IFS, outside of the document root.
ALIASMATCH
----------
AliasMatch does the same thing that Alias does, except it
allows "wildcards" (technically... Regular Expressions.) For
example, I could do something like this:
AliasMatch /foo/(.*jpg) /images/jpg/foo/$1
In a regular expression, a single dot matches any one
character. An asterisk says "zero or more of the preceding
character". So when you have .* it matches any number of any
character. In this example, any URL that begins with /foo/
and ends with jpg will match the alias.
In Apache, the parenthesis designate a section of the URL o
be copied to the resulting URL. So in this example, the
/foo/ is not in parenthesis, but the .*jpg is. So whatever
matches the wildcard of .*jpg will be considered "variable
number 1". You'll notice the result is
/images/jpg/foo/$1 -- that $1 will be replaced at runtime
with whatever matched the .*jpg pattern.
Example:
http://www.example.com/foo/goofy/scott_dancing.jpg
Once the hostname is removed, it starts with /foo/ and ends
with jpg, so it matches the Alias. The (.*jpg) part will
match goofy/scott_dancing.jpg, so Apache will access the
/images/jpg/foo/goofy/scott_dancing.jpg file in the IFS
FWIW, I tend to avoid AliasMatch (or ScriptAliasMatch) since
they run slower, and IMHO, they're more complicated than I
need for my projects.
SCRIPTALIAS
-----------
If you understood Alias, then ScriptAlias should be easy.
There's really only one difference. Alias is for fetching a
document... it tells Apache which document in the IFS to
fetch. By contrast, ScriptAlias is for running a script or
program. Instead of downloading the program object to the
browser (that's what Alias would do), ScriptAlias tells
Apache to run the program. The output of the program will be
sent to the browser, instead of downloading the program object itself.
Without ScriptAlias:
DocumentRoot /www/myserver/htdocs
http://www.example.com/qgpl/pmu010.pgm
This tells Apache to go to the /www/myserver/htdocs/qgpl
directory and download a program named pmu010.pgm to the browser.
With ScriptAlias:
DocumentRoot /www/myserver/htdocs
ScriptAlias /qgpl /QSYS.LIB/QGPL.LIB
http://www.example.com/qgpl/pmu010.pgm
Hopefully you already understand that /QSYS.LIB in the IFS
provides access to your traditional libraries and their
contents. With that in mind, Apache will build the IFS
pathname of /QSYS.LIB/QGPL.LIB/PMU010.PGM and it will
therefore be equivalent of CALL PGM(QGPL/PMU010)
SCRIPTALIASMATCH
----------------
Same as ScriptAlias, except it now has regular expressions
("wildcards") available. ScriptAliasMatch is to ScriptAlias
what AliasMatch is to Alias.
The installer for CGIDEV2 likes to set things up like this:
ScriptAliasMatch /mylibp(.*).pgm /qsys.lib/mylib.lib/$1.pgm
AliasMatch /mylibh/(.*)\.htm /QSYS.LIB/MYLIB.LIB/HTMLSRC.FILE/$1.mbr
Alias /mylibh/ /QSYS.LIB/MYLIB.LIB/HTMLSRC.FILE/ Alias /mylib/ /mylib/
The ScriptAliasMatch at the top says that any URL that begins
with /mylibp and ends with .pgm should be run as a program in
/qsys.lib/mylib.lib. Contrast these two statements:
ScriptAlias /mylibp /qsys.lib/mylib.lib
ScriptAliasMatch /mylibp(.*).pgm /qsys.lib/mylib.lib/$1.pgm
In the first case, anything that starts with /mylibp
(including files, data areas, queues, user spaces, etc) will
be run as a program from the /QSYS.LIB/MYLIB.LIB library. Of
course, if you list a program object, no problem, it'll run
it. If you list a non-program object, however, Apache will
still try to call it (though, it'll fail with an error.)
In the second case, only URLs that end in .PGM are called.
Apache will forcibly add the .pgm extension to it when it
tries to call it.
Therefore, non-programs will not match this script alias.
Instead, they'll match this one (also from the configs, above)
Alias /mylib/ /mylib/
This tells it to go to the /mylib/ folder of the IFS instead
of the library. So program objects go to the library,
non-program objects go to an IFS folder. If you left off
this extra Alias, it would go to the DocumentRoot instead --
and go to /www/myserver/htdocs/mylib.
Shrug... I personally prefer to go in and delete the CGIDEV2
provided instructions and insert my own. I don't like the
instructions they provide. They're more complicated than
they need to be, IMHO.
But, anyway... hope this all made sense.
--
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