How to download metafiles using a signed applet

B

Brian

I want an applet which, once launched, downloads 3 metafiles (files
that it will need later on to work properly) and proceeds into a
processing phase only if the files have been successfully fetched.

So far I do not have a solution for requesting these files and writing
them locally.

Am I following the right track with URL and HttpURLConnection, or
should I be looking into packages like the Apache Jakarta project?

Is there possibly a more straightforward way to instruct the JRE to go
get file "http://www.foo.com/dist/localdata.dat" and put it at
location "C:\localdata.dat" ?

Is there possibly some correlation between the domain mentioned in my
signing certificate and the domain from which I download any
particular file?

Thanks for any ideas,

Brian Herbert Withun
 
A

Andrew Thompson

I want an applet which, once launched, downloads 3 metafiles

Easy enough done. If they are coming from the same
server, it can be done in a sandboxed applet. A
trusted applet could obtain them from any server
on which they available as a publicly fetchable
resource (assuming the server does not specifically
refuse connections to whatever UA the URLConnection
identifies itself as).
..(files
that it will need later on to work properly) and proceeds into a
processing phase only if the files have been successfully fetched.

So far I do not have a solution for requesting these files

There are a number of ways to do it.
...and writing them locally.

Why do you want to do that?

Andrew T.
 
B

Brian

Easy enough done. If they are coming from the same
server, it can be done in a sandboxed applet. A
trusted applet could obtain them from any server
on which they available as a publicly fetchable
resource (assuming the server does not specifically
refuse connections to whatever UA the URLConnection
identifies itself as).

I'll have a signed applet hosted on a partner's site (not the same
company as identified in the signing cert) The files will be coming
from the same server as the applet, though.

That being said, what is a reasonable *way* to retrieve the files?
I'm new to Java and I'm looking for some best-practices. I have read
about HttpURLConnection and have looked briefly at Jakarta.

What's the equivalent to

C:\XCOPY www.domain.com/dist/file.dat C:\LOCALDATA\
Why do you want to do that?

One of the files is a java-compatible Windows DLL that automotive
repair shops will need when using this applet to interface with their
vehicle VCI. That DLL needs to go into the Windows directory.

...or will Windows LoadLibrary find a DLL within the sandbox?

Brian Herbert Withun
 
A

Andrew Thompson

Brian wrote:

(DLL+metafile applet)
...
I'll have a signed applet hosted on a partner's site (not the same
company as identified in the signing cert) The files will be coming
from the same server as the applet, though.

That being said, what is a reasonable *way* to retrieve the files?

Retrieving them - InputStream. That might sound like a
dumb answer, but to make it more specific and less
dumb, I will add, to use..
a) for a resource available 'loose' on the server -
URL.openStream() for that InputStream
b) for a resource inside a jar file on the applet(/application)'s
classpath, use Class.getResource() for that URL, then see a).

The other side to your question is either using,
or storing and using them. ..
..classpath, Class.getResource(name) for an URL, then a)..
I'm new to Java and I'm looking for some best-practices. I have read
about HttpURLConnection and have looked briefly at Jakarta.

It can be done with HttpURLConnection, but now I
check the JavaDocs, I realise it has a lot of cruft
(over URL) not needed for simply gettting an input
stream.
What's the equivalent to

C:\XCOPY www.domain.com/dist/file.dat C:\LOCALDATA\

(checks) XCOPY Copies files and directory trees.

I'll return to that later (if needed).
One of the files is a java-compatible Windows DLL that automotive
repair shops will need when using this applet to interface with their
vehicle VCI. That DLL needs to go into the Windows directory.

..or will Windows LoadLibrary find a DLL within the sandbox?

Hmm.. OK.

Not in an applet, it must be located in the 'Win' directory
for the applet to use it. *But* a web start based (and
sandboxed) applet or application can use DLLs that are
identified as nativelib's in the launch file (put on the
classpath). The only issue with using a sandboxed JWS
app. remains these metafiles.

Most well behaving DLLs that use external files expect
them to be in the 'same directory' so these could
(find and) use any metafiles supplied at the 'root' of
an archive also on the classpath of the JWS app.

BTW. I just realised this was the first time I'd
mentioned Java web start (JWS) in this thread, so
in case you are unfamiliar with it, check here for
some examples. <http://www.physci.org/jws/>

I am hoping you will abandon the idea of doing this
as an applet. That will be very problematic.

--
Andrew Thompson
http://www.athompson.info/andrew/

Message posted via JavaKB.com
http://www.javakb.com/Uwe/Forums.aspx/java-general/200710/1
 

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