How make working directory files available to WebStart application?

Question

Hello everyone,

We have to make a Java application demo available on Internet using JWS. It goes pretty well; all that's missing is making working directory files available for the application.

We know about the getResource() way... The problem is that we have different plugins for the same application and each one require different files (and often different versions of the same files) in their working directory to work properly. So we just change the working directory when we want the application to have a different behavior.

Currently, the demo is packaged in a signed jar file and it loads correctly until it requires a file from the working directory. Obviously, the Internet users of this demo don't have the files ready. We need a way to make these files available to the WebStart application (read/write access) in its working directory.

We've thought of some things, like having the application download the files itself when it starts, or package them in the jar and extract them on startup.

Looking for advices and/or new ideas. I'll continue working on this... I'll update if I ever find something reliable.

Thank you very much!

Answer 1

Note there is a service you can explicitly ask for, to get file access to the computer (unless you go all the way and ask for full access (which requires signed jar files)).

Then you need to determine where these files need to go - basically you have no idea what is where and whether you may actually write anywhere. You can create tmp-files but those go away.

Would a file system abstraction talking to the JNLP-server do so you store the users data on the server?

Answer 2

I said I would share what I found in my research for something that would fit my needs. Here's what I have so far.

I have found that the concept of current working directory (CWD) does not really make sense in the context of a Java Web Start (JWS) application. This had for effect that I stopped trying to find the CWD of a JWS and started looking for other options.

I have found that (no, I didn't know that) you can refer (using getResource()) to a file in the root directory of a JAR file by simply adding a '/' in front of its name. ("/log4j.properties", for example.) The impact of this is that I can now take any file which is only referred to in a read-only manner in the root of that JAR file (which is really only a ZIP file). You can refer to any file in the root of the JAR file using AnyClass.class.getResourceAsStream. That rules out the problem with read-only files required to run the application, at the cost of a switch in the code telling whether the application is run from a valid CWD or from a JWS context. (You can very simply set a property in the JNLP file of the JWS application and check if that property is set or not to know where to look for the file.)

For write-only files (log files in my case), I used the property , adding a directory with the name of the application: /.appname and added log files to it.

Read/write files (which I don't have in my case) would probably simply go at the same place than write-only files. The software could deal with uploading them somewhere if needed, once modified, I guess.

That's the way I deal with the problem for now.