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Java Forum / General / February 2007Access Data Inside JAR
If this is not the place to ask, I'd appreciate it if you could direct me to the correct place. I am creating an executable JAR from a project that has the following structure (I'm developing in Eclipse): Project - src files - resources - icons - config Inside the config directory is a default config file. If the user does not have a personalized config file, I want the default one to be read into an object and then, when the user is finished, that object will be written to their home directory so they have a personalized config file in the future. The problem is, I can't seem to access the config file. I can access the icons in the icons folder, but I'm stuck on how to get to the config file. (I tried ClassLoader.getSystemResource("resources/config/ config.xml") but that always throws a NullPointerException.) If anybody could point me in the right direction, I'd appreciate it. Thanks .. > The problem is, I can't seem to access the config file. I can access > the icons in the icons folder, but I'm stuck on how to get to the > config file. (I tried ClassLoader.getSystemResource("resources/config/ > config.xml") but that always throws a NullPointerException.) Really? AFAIU, getSystemResource() might return a null URL, but it does not actually throw NPE's itself. OTOH, I would usually *not* use the system class loader for my own application's resources. Instead, I recommend you try plain old 'getResource()'. Once done, print the URL. If it is 'null', it might be that this call has been done too early in the process, using the 'root' (or whatever Sun calls it) class loader that is really only good for classes. Sometimes this can happen if you call it in the program's main(), for example. It is usually better to attempt it from within (for example) a constructor for the class. HTH Andrew T. > If this is not the place to ask, I'd appreciate it if you could direct > me to the correct place. [quoted text clipped - 20 lines] > > If anybody could point me in the right direction, I'd appreciate it. Probably you want to read the data out of this config file, so you should use getResourceAsStream(String name) which will return an InputStream. HTH Phil >> If this is not the place to ask, I'd appreciate it if you could direct >> me to the correct place. [quoted text clipped - 24 lines] > should use getResourceAsStream(String name) which will return an > InputStream. OTOH you might be interested in the fact that there is a Preferences class (java.util.prefs.Preferences) which can handle the config stuff of your app in a nice and platform independent way (also providing defaults when a value is not found). Phil > >> If this is not the place to ask, I'd appreciate it if you could direct > >> me to the correct place. [quoted text clipped - 33 lines] > > - Show quoted text - Thanks for your help Phillip and Andrew. But, the resource is still coming back as "null" no matter what I try to do. Here's the portion of my code in question... URL mainURL = this.getClass().getResource("resources/config/ config.xml"); (I also tried - URL mainURL = this.getClass().getResource("/resources/ config/config.xml"); ) This always returns null. However, this works (if the file isn't packaged in a JAR): File mainFile = new File("resources/config/config.xml"); Any other suggestions? All this config file is is a default file that is used if the user does not have their own personalized config file, so I don't need to write to this config file - only read it. >>>> If this is not the place to ask, I'd appreciate it if you could direct >>>> me to the correct place. [quoted text clipped - 44 lines] > is used if the user does not have their own personalized config file, > so I don't need to write to this config file - only read it. That's why I told you to use getResourceAsStream(). AFAIK you can't open the URL you get back from getResource() as a File (don't ask me why). If you actually want to read something from it use getResourceAsStream() Maybe you also want to use: getClass().getClassLoader().getResourceAsStream("resources/config/config.xml"); or in a static method: Thread.currentThread().getContextClassLoader().getResourceAsStream("resources/config/config.xml") Phil > >>>> If this is not the place to ask, I'd appreciate it if you could direct > >>>> me to the correct place. [quoted text clipped - 59 lines] > > - Show quoted text - The problem isn't in reading what I'm getting back...it's the fact that I'm not getting anything back at all... InputStream stream = getClass().getClassLoader().getResourceAsStrea("/ resources/config/config.xml"); System.out.println(stream); Output... null It's extremely annoying because I can get the images (which are in resources/images) just fine. > > >>>> If this is not the place to ask, I'd appreciate it if you could direct > > >>>> me to the correct place. [quoted text clipped - 75 lines] > > - Show quoted text - Well...now I'm confused... When I run the code as an executable JAR, it works the way you said it should (using an InputStream from the getResourceAsStream(String)). But, when I run the code from Eclipse, the direct file method works. Each method does not work with the other way of running the application (and results in a FileNotFoundException or NullPointException). I prefer the JAR method, but, I still want to be able to run my code via Eclipse since it's great for debugging, etc. Any suggestions on this? > URL mainURL = this.getClass().getResource("resources/config/ > config.xml"); That will be looking for the config.xml in a place relative the class's location in the jar. E.g. if "this" is an instance of my.stuff.MyClass, then the above will be looking for: my/stuff/resource/config/config.xml If that isn't what you want then you should adjust accordingly. It may help to know that when you ask the class's classloader for the resource (instead of asking the class itself directly) the path you provide is taken relative to the root of the containing JAR file (or directory tree). -- chris On Feb 27, 12:46 pm, "Chris Uppal" <chris.up...@metagnostic.REMOVE- THIS.org> wrote: > > URL mainURL = this.getClass().getResource("resources/config/ > > config.xml"); [quoted text clipped - 10 lines] > > -- chris Okay, well, that makes sense (and works when I try it). But why doesn't this work within Eclipse? If I use the System classloader, it works fine in the executable JAR but does not work when I run it within Eclipse? (I know this is more of an Eclipse question - but it is annoying that I can't do the same thing in one method of running that I can do in another method.) Thanks for your help. > On Feb 27, 12:46 pm, "Chris Uppal" <chris.up...@metagnostic.REMOVE- > THIS.org> wrote: [quoted text clipped - 18 lines] > is annoying that I can't do the same thing in one method of running > that I can do in another method.) It should. It works here, both ways (eclipse & jar). Phil Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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