input/output with Java Web Start

Question

I'm working on converting a very simple java desktop application to run in java web start and I'm having all kinds of trouble with the input/output files. Most specifically I can't seem to find any information on how to handle i/o in a web start application. I tried placing the input files in the same folder on my web server as the jar and jnlp file, but it doesn't read it.

I've got one input file that I want to keep on the web server and read into the application from there.

I've got a second file that I want the application to generate on the client machine the first time it's run, and read in from there every time thereafter.

If anyone knows what considerations I need to take for i/o in java web start or can point me towards a resource that explains it I would appreciate it.

Answer 1

You can find out where you were downloaded from with BasicService and then use HTTP to transfer the file. You could also just add them to a jar.

You can store a limited amount of information (I think it currently defaults to 128K/muffin) with PeristenceService.

http://java.sun.com/javase/6/docs/jre/api/javaws/jnlp/

Answer 2

You don't have many choices.

• You could read the file from http new URL(address).openStream()
• You could embed the file in the jar which I believe you don't want to, and then use getResourceAsStream()

You usually store files on the user hard drive using a hidden folder

public final class ApplicationConstants{
  final static String HOMEDIR_STRING = System.getProperty("user.home");
  final static File HOMEDIR = new File(HOMEDIR_STRING);
  final static File CONFIG_DIR = new File(HOMEDIR, ".com.mycompany.myapp");
}
///
if(!ApplicationConstants.CONFIG_DIR.exists()) ApplicationConstants.CONFIG_DIR.mkdirs();

File outputFile = new File(ApplicationConstants.CONFIG_DIR, "my.xx"));