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Date: Sat, 7 Apr 2012 20:10:54 +0400
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 <CABzHfVnr3k78XBaShw-kPX2GvQT4B-s-7k2wfeTbGSHhLJK=Ew@mail.gmail.com>
Subject: Re: Accessing USB drive content from pages served from tomcat6 server
From: Konstantin Kolinko <knst.kolinko@gmail.com>
To: Tomcat Users List <users@tomcat.apache.org>
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2012/4/7  <souvik.datta@wipro.com>:
> Hello Chris,
>
> Thanks a lot for responding to my post.
>
> [Chris]What do you mean "not able to access its content"? Do you get 404s=
?
> 500s? Does the thread hang? Does the JVM crash?
>
> [Souvik]: When I am trying to access the content of usb_1, I am getting 4=
04 error.
> Here are the details:
> HTTP Status 404
> message < This is blank>
> description The requested resource () is not available.
>
> [Souvik]
>
> [Chris]Q:What about starting Tomcat with no USB devices, then trying to a=
ccess the resources, then attaching the devices and trying again?
> Ans: Only usb_0 works.
>
> [Chris]Q:What happens when both devices are connected *before* you start =
Tomcat?
> Ans: Only in this case I could access both the devices.
>
> [Chris] Honestly, I'm not sure why you'd want to run a web server off a d=
evice
> which isn't guaranteed to be available.
>
> [Souvik] Actually I am developing a HTML5 App which would run on an embed=
ded target. One of the functionalities of the application is to allow user =
to playback and browse the media content available in an USB stick. Since I=
 am using Webkit browser so some features of HTML5 do not run from file:// =
url and therefore the pages need to be served from a local web server. I ha=
ve chosen tomcat for that.
>
> So it seems to achieve my goal, I need to first connect usb sticks to all=
 the available usb ports on my target and then start tomcat6. As mentioned =
by you,is the server keeping this information in the cache so that in futur=
e when a USB device is connected to a port, it is able to make that out?
> Is this understanding correct?

1. You are (ab)using Tomcat Autodeployment feature.

If docbase of a webapp is not readable, it really cannot start. (Just
a guess. If you looked at the logs your would see it more clearly).

2. It is possible to control deployment process via JMX. That is to
deploy new contexts when needed - the Manager webapp does that.

But I think that using contexts to display those USB sticks is not a
good thing. One thing to beware is that when application is undeployed
 all its contents is deleted (so you risk to delete all data from that
USB stick).

I think it would be better to write a servlet that will serve static
files from the stick. It should not be hard. It might be based on
Tomcat's DefaultServlet,  but actually yours can be more simple:

1. You do not need to use servlet API to get the resources. You have
to use direct file access using java.io.
2. Your access is read-only. You do not need to support writing.

Best regards,
Konstantin Kolinko

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