@Override
    public AssetInfo locate(AssetManager manager, AssetKey key) {
        String name = key.getName();
        File file = new File(root, name);
        if (file.exists() && file.isFile()){
            try {
                // Now, check asset name requirements
                String canonical = file.getCanonicalPath();
                String absolute = file.getAbsolutePath();
                if (!canonical.endsWith(absolute)){
                    throw new AssetNotFoundException("Asset name doesn't match requirements.\n"+
                                                     "\"" + canonical + "\" doesn't match \"" + absolute + "\"");
                }
            } catch (IOException ex) {
                throw new AssetLoadException("Failed to get file canonical path " + file, ex);
            }
            
            return new AssetInfoFile(manager, key, file);
        }else{
            return null;
        }
    }
<code>FileLocator</code> allows you to specify a folder where to
look for assets. 

@author Kirill Vainer
jme3-core/src/plugins/java/com/jme3/asset/plugins/FileLocator.java