com.newatlanta.appengine.vfs.provider.GaeFileNameParser.java Source code

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Here is the source code for com.newatlanta.appengine.vfs.provider.GaeFileNameParser.java

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/*
 * Copyright 2009 New Atlanta Communications, LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.newatlanta.appengine.vfs.provider;

import org.apache.commons.vfs.*;
import org.apache.commons.vfs.provider.*;

/**
 * Parses GAE URIs and creates {@link GaeFileName} instances. This is an
 * internal GaeVFS implementation class that is
 * normally not referenced directly, but only indirectly via the
 * <a href="http://commons.apache.org/vfs/apidocs/index.html" target="_blank">Apache
 * Commons VFS API</a>. See {@link GaeVFS} as the entry point for application
 * code that interacts with GaeVFS.
 *  
 * @author <a href="mailto:vbonfanti@gmail.com">Vince Bonfanti</a>
 */
public class GaeFileNameParser extends AbstractFileNameParser {

    private static GaeFileNameParser instance = new GaeFileNameParser();

    private GaeFileNameParser() {
    }

    static GaeFileNameParser getInstance() {
        return instance;
    }

    /**
     * Makes sure <code>filename</code> always specifies a path that is within a
     * sub-directory of the webapp root path.
     */
    public FileName parseUri(VfsComponentContext context, FileName baseName, String uri)
            throws FileSystemException {
        StringBuffer name = new StringBuffer();

        // Extract the scheme
        String scheme = UriParser.extractScheme(uri, name);
        if (scheme == null) { // this should never happen
            scheme = "gae";
        }

        // Remove encoding, and adjust the separators
        UriParser.canonicalizePath(name, 0, name.length(), this);
        UriParser.fixSeparators(name);

        // Normalise the path
        FileType fileType = UriParser.normalisePath(name);

        // all GAE files *must* be relative to the root file, which must be the
        // webapp root (though we have no way of enforcing this)
        String rootPath = "";
        if (baseName == null) { // this is the root object
            rootPath = name.toString();
            name.setLength(0);
        } else {
            rootPath = getRootPath(baseName);
            if (name.indexOf(rootPath) == 0) { // if ( name.startsWith( basePath ) )
                name.delete(0, rootPath.length());
            }
        }
        return new GaeFileName(scheme, rootPath, name.toString(), fileType);
    }

    public static String getRootPath(FileName baseName) throws FileSystemException {
        FileName rootName = baseName.getRoot();
        if (rootName instanceof GaeFileName) {
            return ((GaeFileName) rootName).getRootPath();
        } else {
            StringBuffer rootPath = new StringBuffer();
            UriParser.extractScheme(baseName.getURI(), rootPath);
            UriParser.normalisePath(rootPath);
            return rootPath.toString().intern();
        }
    }
}