Jonathan Mast wrote:
Andre, its one single, physical app/docBase, mapped to multiple contexts
(which happen to located on different virtual hosts). This is a
requirement.
It seems to be a bad requirement then, see
http://tomcat.apache.org/tomcat-6.0-doc/virtual-hosting-howto.html
I believe (but we need a real expert here) that having multiple <Host>
entries sharing the same appBase is a receipe for problems.
If it is really just to have a single copy of the code on disk however,
you may be able to get away with having multiple (differently named)
appBase attributes, but all symlinked to the same physical location, see
below.
I must say that I don't really understand the requirement, unless your
"fruit" webapp is really big (in disk size), or you have many different
"fruit" hosts.
You can have this :
<Host name"apples.company.com" appBase="webapps-apples">
<Host name"pears.company.com" appBase="webapps-pears">
<Host name"lemons.company.com" appBase="webapps-lemons">
and then have
(CATALINA_BASE)/webapps-apples/ROOT/your webapp code
(CATALINA_BASE)/webapps-pears/ROOT/your webapp code
(CATALINA_BASE)/webapps-lemons/ROOT/your webapp code
and still, browsers would access your webapp by URLs like
http://apples.company.com
http://pears.company.com
http://lemons.company.com
and they would all get your same webapp
The above is if your want to make your "fruit" webapp be the default webapp.
Alternatively, you could have
<Host name"apples.company.com" appBase="webapps-apples">
<Host name"pears.company.com" appBase="webapps-pears">
<Host name"lemons.company.com" appBase="webapps-lemons">
and then have
(CATALINA_BASE)/webapps-apples/fruit/your webapp code
(CATALINA_BASE)/webapps-pears/fruit/your webapp code
(CATALINA_BASE)/webapps-lemons/fruit/your webapp code
and browsers would access your webapp by URLs like
http://apples.company.com/fruit
http://pears.company.com/fruit
http://lemons.company.com/fruit
and they would all get your same webapp
but in each case, during the deployment and initialisation of your
webapp, each of the "fruit" instances, during it's own init(), could
through getServerName() get its own Host's "name", and initialise
accordingly.
So, as per your requirement
http://apples.company.com/fruit would get an apple
http://pears.company.com/fruit would get a pear
If you absolutely want to save disk space, the each of "webapps-apples",
"webapps-pears" and "webapps-lemons", could be a symlink to
"webapps-00common", and the code could really be stored there.
Like :
(CATALINA_BASE)/webapps-00common/fruit/your webapp code
(CATALINA_BASE)/webapps-apples (link to 00common)
(CATALINA_BASE)/webapps-pears (link to 00common)
(CATALINA_BASE)/webapps-lemoms (link to 00common)
But I have no idea how Tomcat would react if, for instance, you did a
new deployment of your webapp (replace the files).
That's what I mean by "receipe for problems" above.
I think unless you really have many fruit, it's better to avoid that.
All of the above is predicated on the asumption that you really need to
do this specific per-host initialisation ahead of time.
If you don't, then you could use a single <Host> entry, pick up the
hostname at request processing time, and do away with all the setup above.
Don't forget the maxim : "Premature optimisation is the root of much evil".
How many "fruit" are we really talking about ?
The /META-INF/context.xml approach is ruled out by this requirement.
There are alternatives to that, see here :
http://tomcat.apache.org/tomcat-6.0-doc/config/context.html
My goal is to have a layer of code takes a the current host (eg.
apples.mysite.com) looks it up in a database where it is linked to
host-specific content. After this stage, the showFruit.jsp will display an
Apple and so on.
- have your webapp (actually I guess, the first servlet) in it's init()
code, get the hostname from getServerName() and
perform whatever setup it needs to. Then save this in an attribute of the
ServletContext
But where do I find this elusive init() method?
javax.servlet.Servlet
inherited by HttpServlet.
Here is an example :
http://java.sun.com/products/servlet/articles/tutorial/
On Wed, Jun 24, 2009 at 5:01 PM, André Warnier <a...@ice-sa.com> wrote:
Hi.
I am one of the least Tomcat and Java qualified people that regularly lurk
on this forum, so don't take my word for any of what follows.
Let's say that I am just trying to apply what I think I have learned here.
And I am eager for contradiction, because it is said that this is how one
learns.
Jonathan Mast wrote:
I have a webapp that I would like to behave in a context (actually
host)-specific manner. Where is the best place to initialize the
context/host specific functionality?
Let me demonstrate what I'm talking about. Lets say I have a webapp Fruit
located in folder webapps/fruit.
I want to define:
apples.mysite.com
bananas.mysite.com
coconuts.mysite.com
etc ...
all of which point to webapps/fruit (these are hosts with a "/" context
pointing to "webapps/fruit" as the docBase, to be more precise).
appBase ?
Do you mean all Hosts point to the *same physical* webapps/fruit, or does
each Host have its own copy in a separate directory ?
When someone visits apples.mysite.com they see an apple, when they visit
bananas.mysite.com they see a banana, and so on.
Where in the fruit app is the best place for instance of Fruit to
introspect
itself (basically look for what host name it is defined under) and prepare
accordingly?
I've looked into using Context Parameters in the server.xml declarations
That would probably better be in a /META-INF/context.xml, no ?
(at least if these are distinct webapp/fruit)
or see here for more complete info :
http://tomcat.apache.org/tomcat-6.0-doc/config/context.html
but
I would like to avoid this if possible b/c this functionally is more
elegantly determined through introspection (the web-app saying "what host
do
i belong to?").
Of course I could always call request.getLocalName(),
I think you want getServerName(), or you'd always get the same DNS name/IP,
no matter wich virtual Host is called..
but that would be
inefficient as it would have to be invoked on every request.
I guess what I'm looking for someplace in the context initialization
process
where i could hook into and do my stuff and have it apply to the entire
context throughout it's lifecycle. Can't seem to find it digging around
the
javax.servlet.* javadocs.
I reason as follows :
- a webapp is run by a thread
- a thread is started by a Connector
- I don't think that a thread is Host-specific, in the sense that it can
run one webapp for one Host, and the next instant run another webapp for
another Host.
What I'm saying is that I am not sure that above the Request level, you
will find anything that is "Host-persistent" to keep your stuff in and
retrieve it (I mean for webapps shared by several Hosts, which is probably a
bad idea anyway).
To this eager student thus, the correct way to do what I understand you
want to do, seems to be :
- have each Host have its own appBase (webapp dir), with in each a copy of
your (identical) webapp code "Fruit".
- have your webapp (actually I guess, the first servlet) in it's init()
code, get the hostname from getServerName() and perform whatever setup it
needs to. Then save this in an attribute of the ServletContext
- which should then be available at each subsequent execution of any
servlet composing the webapp
Inspired by the Servlet Spec 2.5, section 2.3 Servlet lifecyle, 2.3.2
Initialization.
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