Help with writing to the JWS cache directory?

Question

We have a java application named "foo" that we would like to deploy via Webstart. The original version of foo is packaged into a single foo.jar archive. Foo creates a textfile "info.txt" outside of foo.jar. "Info.txt" stores information that we would like to remain constant for each client machine, which is why we are not wrapping this info inside foo.jar b/c "foo.jar" is overwritten each time a new version is available on the server.
When running "java -jar foo.jar" outside of Webstart, foo works correctly and generates "info.txt" in the same directory where foo.jar is located. The current directory is determined by this code snippet--
File infoFile = new File ( "info.txt");
However, when we deploy "foo.jar" through Webstart, foo fails to work properly on the client machine b/c it is unable to write "info.txt" in the directory where "foo.jar" has been downloaded and cached. Note that we have signed foo.jar properly and it is allowed to write to the local filesystem. But instead of generating "info.txt" in the same location as "foo.jar", it creates "info.txt" on the client desktop causing problems with the running application.
Can anyone tell us how to capture the client's cache directory location during Webstart download so that "info.txt" can be created and placed in that directory?

Answer 1

you can find the path to the cache directory by getting a jar url to one of your resources in the cache:
URL jarURL = this.getClass().getClassLoader().getResource("MyClass.class");
String jarFileStr = jarURL.getFile();
1.) first remove the "!/MyClass.class":
jarFileStr = jarFileStr.substring(0, jarFileStr.length() - "!/MyClass.class".length());
2.) then remove the jar://file: in front:
if (jarFileStr.startsWith("jar://file:") { jarFileStr = jarFileStr.substr(11); }
3.) may need to transform %20 to spaces, and forward slashes to File.seperator
jarFileStr.replace("%20", " ");
This gives me a string value of:
file:C:/Documents%20and%20Settings/glyn/.javaws/cache/http/Dgwwinxp/P80/DMlive/DMjava/RMBBClient.jar
When I try to do:
File jarFile = new File(jarFileStr);
JarFile jar = new JarFile(jarFile);
I get java.util.zip.ZipException: The filename, directory name, or volume label syntax is incorrect.
Has anyone got this method of getting the jar file to work?
Thanks
Glyn
Re: Java Web Start getResource() issue
Author: dietz333
In Reply To: Re: Java Web Start getResource() issue      Sep 29, 2003 10:18 AM
Reply 5 of 8
Glenn:
the string - file:C:/Documents%20and%20Settings/glyn/... is not legal path.
1.) first you need to strip off the "file:"
2.) you need to change the '/' to '\' (on windows).
use str.replaceAll("/", File.separator)
/dietz
Re: Java Web Start getResource() issue
Author: gdub
In Reply To: Re: Java Web Start getResource() issue      Sep 30, 2003 9:29 AM
Reply 6 of 8
Thanks for the reply.
I changed the line to
jarFileStr = jarFileStr.substring("file:".length(), jarFileStr.length() - "!/com/xxxx".length());
File file = new File(jarFileStr);
The System.out of file is
C:\Documents%20and%20Settings\glyn\.javaws\cache\http\Dgwwinxp\P80\DMlive\DMjava\RMMyApp.jar but isExists() returns false on the file.
I guess it doesn't like the %20 etc. because that it the path to the file alright..
Re: Java Web Start getResource() issue
Author: gdub
In Reply To: Re: Java Web Start getResource() issue      Sep 30, 2003 9:33 AM
Reply 7 of 8
This works:
jarFileStr = jarFileStr.substring("file:".length(), jarFileStr.length() - "!/com/xxxx".length());
jarFileStr.replaceAll("%20", " ");
File file = new File(jarFileStr);
Not very pretty. But it will do me for now.
Thanks for your help.
Re: Java Web Start getResource() issue
Author: josephconder
In Reply To: Re: Java Web Start getResource() issue      Oct 3, 2003 1:43 PM
Reply 8 of 8
I ran into this problem as well. The string is URL encoded (hence the %20=space).
You could use URLDecoder.decode(jarFileStr) to get the same result (and not worry about any other encoded characters).