java web start jars

Hello,

I'm a student at the university of Antwerp Belgium and I'm writing a
program for java web start that has to support plugins.
Now my question is why does java web start download 3 versions of the
resources specified in the jnlp file: RC*.jar, RM*.jar and RT*.jar and
is there any way in which I can acces the jar files in the following
way:


String url = "location of jar file downloaded by java web start"
URL u = new URL("jar", "", url + "!/");
JarURLConnection uc = (JarURLConnection)u.openConnection();
JarFile jar = uc.getJarFile();
Manifest man = jar.getManifest();
Attributes attr = man.getMainAttributes();

this always throws the following exception no matter which version
(rm,rc,rt) I access.
I/O error while loading JAR file:
java.util.zip.ZipException: The system cannot find the file specified
at java.util.zip.ZipFile.open(Native Method)
at java.util.zip.ZipFile.<init>(Unknown Source)
at java.util.jar.JarFile.<init>(Unknown Source)
at java.util.jar.JarFile.<init>(Unknown Source)
at sun.net.www.protocol.jar.URLJarFile.<init>(Unknown Source)
at sun.net.www.protocol.jar.URLJarFile.getJarFile(Unknown Source)
at sun.net.www.protocol.jar.JarFileFactory.get(Unknown Source)
at sun.net.http://www.protocol.jar.JarURLConnec...onnect(Unknown Source)
at sun.net.http://www.protocol.jar.JarURLConnec...arFile(Unknown
Source)
at PluginClassLoader.getMainClassName(PluginClassLoad er.java:28)
at PluginRunner.run(PluginRunner.java:30)
at Notepad.main(Notepad.java:78)

although the file I specify in the url is in the java web start cache
directory

thx.

re: java web start jars

On 5 Apr 2004 02:14:08 -0700, vde_steven@hotmail.com (Steven) wrote or
quoted :
[color=blue]
>String url = "location of jar file downloaded by java web start"
>URL u = new URL("jar", "", url + "!/");[/color]

jar:file:///C|/bar/baz.jar!/com/foo/Quux.class

Is used for accessing a member of jar. If you want the entire jar,
you use a url like this

file:///C|/bar/baz.jar
--
Canadian Mind Products, Roedy Green.
Coaching, problem solving, economical contract programming.
See http://mindprod.com/jgloss/jgloss.html for The Java Glossary.

re: java web start jars

Hello Stefen,

Did you finally managed to access the jar files and do you know the use of RC*.jar, RM*.jar and RT*.jar ?

If yes, can you please tell us about it.

I'm actually trying to know when Java Web Start has updated an application so I can display a special screen (ONLY IF updates have been made). And I figured I could get some info from those three jars.

If you have any better idea, feel free to post.

Thanks in advance,

Alex.