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Re: [scala] problem with getResource

by Meredith Gregory :: Rate this Message:

Christos,

Many thanks for your reply. In my experimentation i did find that the ClassLoader returned from getContextClassLoader is indeed a URLClassLoader. i note that there is a big difference between your system and mine: your box is running some version of Windows, while my MacBook Pro is running the latest update of Leopard.

As for relying on classloaders... unfortunately the code is not mine to make that decision. i'm integrating some Scala functionality with CAL functionality. The Quark/CAL initialization is failing here because the getResource method is returning null under every invocation i can think of. Since i have the CAL source i looked through it relatively carefully. i believe they wrote it this way by way of following their interpretation of best practices. Moreover, i tried putting in a small hack of the form replacing

       if (folderFile == null) {
            return null;
        }

with

      if (folderFile == null) {
            try {
                File lastChanceFile = new File(new File(".").getCanonicalPath() + filePath.getPathString());
                if (lastChanceFile.exists()) {
                    return lastChanceFile;
                }
            } catch (java.io.IOException e) {
                return null;
            }
            return null;
        }

But even though this actually returns the file, all hell breaks loose further on. So, i think what i have to do is attempt invoke the Scala code that calls the CAL/Quark API with the exact same environment that they use in the ICE.sh invocation script. My guess is that they never got a chance to test their APIs in a inter-JVM-language situation.

Best wishes,

--greg

On Wed, Jul 23, 2008 at 12:45 AM, Christos KK Loverdos <loverdos@...> wrote:

Hi Gregory,

Generally speaking, do not rely on classloaders to follow your path in the disk. Now, to your case, I cannot reproduce the behaviour (I have made the folder and files as in your case):

C:\>java-apps\scala-2.7.1-final\bin\scala -Xnojline
Welcome to Scala version 2.7.1.final (Java HotSpot(TM) Client VM, Java 1.6.0_07).

Type in expressions to have them evaluated.
Type :help for more information.

scala> new java.io.File("WorkspaceDecls")

res0: java.io.File = WorkspaceDecls

scala> res0.listFiles()

res1: Array[java.io.File] = Array(WorkspaceDecls\App.class, WorkspaceDecls\gemcutter.default.cws)

scala> java.lang.Thread.currentThread().getContextClassLoader()
res2: java.lang.ClassLoader = java.net.URLClassLoader@354093

scala> res2.getResource("WorkspaceDecls/gemcutter.default.cws")

res3: java.net.URL = file:/C://WorkspaceDecls/gemcutter.default.cws

Since in Scala 2.7.1 the context class loader is a URLClassLoader, please do the following, just to see if the folder containing WorkspaceDecls is the classpath of the classloader:

scala> res2.asInstanceOf[java.net.URLClassLoader].getURLs

If you don't see it here, then you get normal behaviour. Otherwise, we shall have to dig a little further :-)

BR
Christos

On 7/23/08, Meredith Gregory <lgreg.meredith@...> wrote:

Scalads and Lasses,

Please see the trace below. The method getResource on java.lang.Thread.currentThread().getContextClassLoader() is not behaving as i expect it would. It never returns anything but null as far as my experimentation has gone. Any help would be greatly appreciated.

Best wishes,

--greg

[INFO] [scala:console]
Welcome to Scala version 2.7.1.final (Java HotSpot(TM) Client VM, Java 1.5.0_13).
Type in expressions to have them evaluated.
Type :help for more information.

scala> new java.io.File("WorkspaceDecls")
new java.io.File("WorkspaceDecls")
new java.io.File("WorkspaceDecls")
res0: java.io.File = WorkspaceDecls

scala> res0.listFiles()
res0.listFiles()
res0.listFiles()
res1: Array[java.io.File] = Array(WorkspaceDecls/App.class, WorkspaceDecls/gemcutter.default.cws)

scala> java.lang.Thread.currentThread().getContextClassLoader()
java.lang.Thread.currentThread().getContextClassLoader()
java.lang.Thread.currentThread().getContextClassLoader()
res2: java.lang.ClassLoader = java.net.URLClassLoader@697c4

scala> res2.getResource("WorkspaceDecls/gemcutter.default.cws")
res2.getResource("WorkspaceDecls/gemcutter.default.cws")
res2.getResource("WorkspaceDecls/gemcutter.default.cws")
res3: java.net.URL = null

scala> new java.io.File(".").getCanonicalPath()
new java.io.File(".").getCanonicalPath()
new java.io.File(".").getCanonicalPath()
res4: java.lang.String = /Users/lgm/work/src/projex/bobj/magritte/pipe-cutter/pipes_to_cal

scala> res2.getResource(new java.io.File(".").getCanonicalPath() + "WorkspaceDecls/gemcutter.default.cws")
res2.getResource(new java.io.File(".").getCanonicalPath() + "WorkspaceDecls/gemcutter.default.cws")
res2.getResource(new java.io.File(".").getCanonicalPath() + "WorkspaceDecls/gemcutter.default.cws")
res5: java.net.URL = null

scala>

--
L.G. Meredith
Managing Partner
Biosimilarity LLC
806 55th St NE
Seattle, WA 98105

+1 206.650.3740

http://biosimilarity.blogspot.com

--
  __~O
-\ <,       Christos KK Loverdos
(*)/ (*)      http://ckkloverdos.com

--
L.G. Meredith
Managing Partner
Biosimilarity LLC
806 55th St NE
Seattle, WA 98105

+1 206.650.3740

http://biosimilarity.blogspot.com

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