Add 'asset' URLConnection; IOUtil uses URLConnection / incr. effeciency; Android ClassLoaderUtil cleanup;

- Add 'asset' URLConnection
  - Please read API doc 'PiggybackURLConnection' and 'AssetURLConnection'

  - Solves generic resource handling where platform locations may differ,
    ie ClassLoader lookup on Android in the 'assets/' subfolder.

  - New Android 'AssetDexClassLoader' uses 'assets/' folder for findResource(..)

  - aapt.signed (our APK ant task)
    - uses 'assets/' folder

    - adds the 'assetsdir' attribute allowing to copy other assets into the APK

- IOUtil uses URLConnection / incr. effeciency
  - using URLConnection on all getResource(..) since URL
    is connected anyways for validation and URLConnection can be used by caller right away

  - String getRelativeOf(URL, String) -> URL getRelativeOf(URL, String)
    - preserves scheme, authority, etc
    - simple parentOf handling, more efficient

  - reusing new 'asset' protocol impl.

- Android ClassLoaderUtil cleanup;
  - Use createClassLoader(..) impl for build-in static jogamp and user APKs,
    which removes code redundancy

Tests: New code path, especially 'assets' are covered by new unit tests, no regressions on Linux.

1 files changed, 212 insertions, 0 deletions

diff --git a/src/java/com/jogamp/common/net/AssetURLContext.java b/src/java/com/jogamp/common/net/AssetURLContext.java
new file mode 100644
index 0000000..00c7df7
--- /dev/null
+++ b/src/java/com/jogamp/common/net/AssetURLContext.java
@@ -0,0 +1,212 @@
+package com.jogamp.common.net;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.net.URLConnection;
+import java.net.URLStreamHandler;
+
+import jogamp.common.Debug;
+
+import com.jogamp.common.os.AndroidVersion;
+import com.jogamp.common.util.IOUtil;
+
+/**
+ * See {@link PiggybackURLConnection} for description and examples.
+ */
+public abstract class AssetURLContext implements PiggybackURLContext {
+    private static final boolean DEBUG = Debug.isPropertyDefined("jogamp.debug.IOUtil", true);
+    
+    /** The <i>asset URL</i> protocol name <code>asset</code> */
+    public static final String asset_protocol = "asset";
+    
+    /** The <i>asset URL</i> protocol prefix <code>asset:</code> */
+    public static final String asset_protocol_prefix = "asset:";
+    
+    /** 
+     * The <i>optional</i> <i>asset</i> folder name with ending slash <code>assets/</code>.
+     * <p>
+     * Note that the <i>asset</i> folder is not used on all platforms using the <i>asset</i> protocol
+     * and you should not rely on it, use {@link AssetURLConnection#getEntryName()}.
+     * </p>
+     **/
+    public static final String assets_folder = "assets/";
+
+    public static AssetURLContext create(final ClassLoader cl) {
+        return new AssetURLContext() {
+            @Override
+            public ClassLoader getClassLoader() {
+                return cl;
+            }
+        };
+    }
+    
+    public static AssetURLStreamHandler createHandler(final ClassLoader cl) {
+        return new AssetURLStreamHandler(create(cl));
+    }
+    
+    /**
+     * Create an <i>asset</i> URL, suitable even w/o the registered <i>asset</i> URLStreamHandler.
+     * <p>
+     * This is equivalent with:
+     * <pre>
+     *   return new URL(null, path.startsWith("asset:") ? path : "asset:" + path, new AssetURLStreamHandler(cl));
+     * </pre>
+     * </p>
+     * @param path resource path, with or w/o <code>asset:</code> prefix
+     * @param cl the ClassLoader used to resolve the location, see {@link #getClassLoader()}.
+     * @return
+     * @throws MalformedURLException
+     */
+    public static URL createURL(String path, ClassLoader cl) throws MalformedURLException {
+        return new URL(null, path.startsWith(asset_protocol_prefix) ? path : asset_protocol_prefix + path, createHandler(cl));
+    }
+    
+    /**
+     * Create an <i>asset</i> URL, suitable only with the registered <i>asset</i> URLStreamHandler.
+     * <p>
+     * This is equivalent with:
+     * <pre>
+     *   return new URL(path.startsWith("asset:") ? path : "asset:" + path);
+     * </pre>
+     * </p>
+     * @param path resource path, with or w/o <code>asset:</code> prefix
+     * @return
+     * @throws MalformedURLException
+     */
+    public static URL createURL(String path) throws MalformedURLException {
+        return new URL(path.startsWith(asset_protocol_prefix) ? path : asset_protocol_prefix + path);
+    }
+    
+    /**
+     * Returns the <i>asset</i> handler previously set via {@link #registerHandler(ClassLoader)}, 
+     * or null if none was set.
+     */
+    public static URLStreamHandler getRegisteredHandler() {
+        final GenericURLStreamHandlerFactory f = GenericURLStreamHandlerFactory.register();
+        return ( null != f ) ? f.getHandler(asset_protocol) : null;
+    }
+    
+    /**
+     * Registers the generic URLStreamHandlerFactory via {@link GenericURLStreamHandlerFactory#register()} 
+     * and if successful sets the <i>asset</i> <code>handler</code> for the given ClassLoader <code>cl</code>.
+     * 
+     * @return true if successful, otherwise false
+     */
+    public static boolean registerHandler(ClassLoader cl) {
+        final GenericURLStreamHandlerFactory f = GenericURLStreamHandlerFactory.register();
+        if( null != f ) {
+            f.setHandler(asset_protocol, createHandler(cl));
+            return true;
+        } else {
+            return false;
+        }
+    }
+    
+    /** 
+     * Returns an <i>asset</i> aware ClassLoader.
+     * <p>
+     * The ClassLoader is required to find the <i>asset</i> resource 
+     * via it's <code>URL findResource(String)</code> implementation.
+     * </p>
+     * <p>
+     * It's <code>URL findResource(String)</code> implementation shall return either
+     * an <i>asset</i> URL <code>asset:sub-protocol</code> or just the sub-protocol URL.
+     * </p>
+     * <p>
+     * For example, on Android, we <i>redirect</i> all <code>path</code> request to <i>assets/</i><code>path</code>.
+     * </p>
+     */
+    public abstract ClassLoader getClassLoader();
+
+    @Override
+    public String getImplementedProtocol() {
+        return asset_protocol;
+    }        
+    
+    /**
+     * {@inheritDoc}
+     * <p> 
+     * This implementation attempts to resolve <code>path</code> in the following order:
+     * <ol>
+     *   <li> as a valid URL: <code>new URL(path)</code>, use sub-protocol if <i>asset</i> URL</li>
+     *   <li> via ClassLoader: {@link #getClassLoader()}.{@link ClassLoader#getResource(String) getResource(path)}, use sub-protocol if <i>asset</i> URL </li>
+     *   <li> as a File: <code>new File(path).toURI().toURL()</code>
+     * </ol>
+     * </p> 
+     * <p>
+     * In case of using the ClassLoader (2) <b>and</b> if running on Android,
+     * the {@link #assets_folder} is being prepended to <code>path</code> if missing.
+     * </p> 
+     **/    
+    @Override
+    public URLConnection resolve(String path) throws IOException {
+        return resolve(path, getClassLoader());
+    }
+    
+    public static URLConnection resolve(String path, ClassLoader cl) throws IOException {
+        URL url = null;
+        URLConnection conn = null;
+        int type = -1;
+        
+        if(DEBUG) {
+            System.err.println("AssetURLContext.resolve: <"+path+">");
+        }
+        
+        try {
+            // lookup as valid sub-protocol
+            url = new URL(path);
+            conn = open(url);
+            type = null != conn ? 1 : -1;
+        } catch(MalformedURLException e1) { if(DEBUG) { System.err.println("ERR: "+e1.getMessage()); } }
+        
+        if(null == conn && null != cl) {
+            // lookup via ClassLoader .. cleanup leading '/'
+            String cpath = path;
+            while(cpath.startsWith("/")) {
+                cpath = cpath.substring(1);
+            }
+            if(AndroidVersion.isAvailable) {
+                cpath = cpath.startsWith(assets_folder) ? cpath : assets_folder + cpath;
+            }
+            url = cl.getResource(cpath);
+            conn = open(url);
+            type = null != conn ? 2 : -1;
+        }
+        
+        if(null == conn) {
+            // lookup as File
+            try {
+                File file = new File(path);
+                if(file.exists()) {
+                    url = IOUtil.toURLSimple(file);
+                    conn = open(url);
+                    type = null != conn ? 3 : -1;
+                }
+            } catch (Throwable e) { if(DEBUG) { System.err.println("ERR: "+e.getMessage()); } }
+        }
+        
+        if(DEBUG) {
+            System.err.println("AssetURLContext.resolve: type "+type+": url <"+url+">, conn <"+conn+">, connURL <"+(null!=conn?conn.getURL():null)+">");
+        }
+        if(null == conn) {
+            throw new FileNotFoundException("Could not look-up: "+path+" as URL, w/ ClassLoader or as File");
+        }
+        return conn;
+    }
+    
+    private static URLConnection open(URL url) {
+        if(null==url) {
+            return null;
+        }
+        try {
+            final URLConnection c = url.openConnection();
+            c.connect(); // redundant
+            return c;
+        } catch (IOException ioe) { if(DEBUG) { System.err.println("ERR: "+ioe.getMessage()); } } 
+        return null;
+    }
+    
+}