SMACK-286 Made ProviderManager much more configurable.

Separated the reading of provider files from the ProviderManager.  Manager now only manages.  Added ability to add collections of providers to the manager via a ProviderLoader, of which there is one default implementation which loads from the default file format.  Now provider files can be programmatically added at any time.  Also updated the configuration abilities so that a provider file can also be set via VM arg, as well as the smack configuration itself. Introduced Java Util Logging as well.

git-svn-id: http://svn.igniterealtime.org/svn/repos/smack/branches/smack_3_4_0@13861 b35dd754-fafc-0310-a699-88a17e54d16e

source/org/jivesoftware/smack/util/FileUtils.java

@@ -0,0 +1,59 @@
+package org.jivesoftware.smack.util;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.MalformedURLException;
+import java.net.URI;
+import java.util.ArrayList;
+import java.util.List;
+
+public final class FileUtils {
+
+    private FileUtils() {
+    }
+    
+    public static InputStream getStreamForUrl(String url, ClassLoader loader) throws MalformedURLException, IOException {
+        URI fileUri = URI.create(url);
+        
+        if (fileUri.getScheme() == null) {
+            throw new MalformedURLException("No protocol found in file URL: " + url);
+        }
+        
+        if (fileUri.getScheme().equals("classpath")) {
+            // Get an array of class loaders to try loading the providers files from.
+            ClassLoader[] classLoaders = getClassLoaders();
+            for (ClassLoader classLoader : classLoaders) {
+                InputStream is = classLoader.getResourceAsStream(fileUri.getSchemeSpecificPart());
+                
+                if (is != null) {
+                    return is;
+                }
+            }
+        }
+        else {
+            return fileUri.toURL().openStream();
+        }
+        return null;
+    }
+    
+    /**
+     * Returns default classloaders.
+     *
+     * @return an array of ClassLoader instances.
+     */
+    public static ClassLoader[] getClassLoaders() {
+        ClassLoader[] classLoaders = new ClassLoader[2];
+        classLoaders[0] = FileUtils.class.getClassLoader();
+        classLoaders[1] = Thread.currentThread().getContextClassLoader();
+        // Clean up possible null values. Note that #getClassLoader may return a null value.
+        List<ClassLoader> loaders = new ArrayList<ClassLoader>();
+
+        for (ClassLoader classLoader : classLoaders) {
+            if (classLoader != null) {
+                loaders.add(classLoader);
+            }
+        }
+        return loaders.toArray(new ClassLoader[loaders.size()]);
+    }
+
+}