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java web start jars

P: n/a

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
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: The system cannot find the file specified
at Method)
at<init>(Unknown Source)
at java.util.jar.JarFile.<init>(Unknown Source)
at java.util.jar.JarFile.<init>(Unknown Source)
at<init>(Unknown Source)
at Source)
at Source)
at Source)
at PluginClassLoader.getMainClassName(PluginClassLoad
at Notepad.main(

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

Jul 17 '05 #1
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2 Replies

P: n/a
On 5 Apr 2004 02:14:08 -0700, vd******** (Steven) wrote or
quoted :
String url = "location of jar file downloaded by java web start"
URL u = new URL("jar", "", url + "!/");


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

Canadian Mind Products, Roedy Green.
Coaching, problem solving, economical contract programming.
See for The Java Glossary.
Jul 17 '05 #2

P: 1
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,

Nov 9 '05 #3

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