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Groups > comp.lang.java.programmer > #11628

Re: Resource confusion

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Arved Sandstrom wrote:
> If you're going to use .getResource(), the String "name" that you supply
> is actually a '/'-separated path name that identifies something on a
> classloader classpath. You have a number of classloaders involved every
> time you run your app; fact is that your phrase-list file (even if you
> had a '/'-separated path spec for it) very likely isn't on the classpath
> for any of those classloaders.
>
> It doesn't sound to me like you need either the getResource() or
> getResourceAsStream() approaches (which are available through
> ClassLoader or delegated from Class); you might be better off saving and
> using file URLs.
>
> The exact form of a file URL varies across systems but they all have the
> file: scheme. On a UNIX system
>
> URL phraseListUrl = new URL("file:///home/me/Games/PhraseLists");
>
> would work, but off the top of my head on a Windows box it's something like
>
> URL phraseListUrl = new URL("file:///C:/Games/PhraseLists");
>
> This is just informational, because your app doesn't have to construct
> these things, just save them. Your user does the heavy lifting by
> selecting the location with a file chooser; that gives you a File
> object. You can save out the result with
>
> userSelectedFile.toURI().toURL().toString()
>
> To return to getResource() or getResourceAsStream(), and classloaders:
> the situation is more complicated in Java application server
> environments [1], and for this reason context classloaders were made
> available as (imperfect) solutions. But you are not in that scenario.
>
> I'll also add that *if* it made sense for you to have a file resource on
> the classpath, and you were using getResource() or
> getResourceAsStream(), it doesn't make sense for you to pose the
> question "which classloader should I use?" That's not *your* decision to
> make, per se - you can influence that choice by where you place the
> resource, but you don't directly select a classloader (again, unless you
> were in a server environment and using a context classloader).
>
> AHS
>
> 1. As anyone can attest who has spent quality hours wrestling with a
> situation where instance 1 of class X hasn't the same class as instance
> 2 of class X...for various reasons.

What he said, only adding tangentially that at some not-too-distant future 
point it pays to understand classloading in Java.

-- 
Lew
Honi soit qui mal y pense.
http://upload.wikimedia.org/wikipedia/commons/c/cf/Friz.jpg

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Resource confusion Novice <novice@example..com> - 2012-01-28 17:47 +0000
  Re: Resource confusion Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-28 15:44 -0400
    Re: Resource confusion Lew <noone@lewscanon.com> - 2012-01-28 13:43 -0800
    Re: Resource confusion Novice <novice@example..com> - 2012-01-29 05:40 +0000
      Re: Resource confusion Lew <noone@lewscanon.com> - 2012-01-28 22:43 -0800
      Re: Resource confusion Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-29 13:24 -0400
  Re: Resource confusion Roedy Green <see_website@mindprod.com.invalid> - 2012-01-30 13:33 -0800
    Re: Resource confusion Martin Gregorie <martin@address-in-sig.invalid> - 2012-01-31 02:45 +0000
      Re: Resource confusion Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-31 06:32 -0400
        Re: Resource confusion Martin Gregorie <martin@address-in-sig.invalid> - 2012-01-31 20:43 +0000
          Re: Resource confusion Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-31 18:08 -0400
            Re: Resource confusion Martin Gregorie <martin@address-in-sig.invalid> - 2012-01-31 23:01 +0000

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