de.fhg.igd.mapviewer.cache.FileTileCache.java Source code

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Here is the source code for de.fhg.igd.mapviewer.cache.FileTileCache.java

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/*
 * Copyright (c) 2016 Fraunhofer IGD
 * 
 * All rights reserved. This program and the accompanying materials are made
 * available under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 3 of the License,
 * or (at your option) any later version.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution. If not, see <http://www.gnu.org/licenses/>.
 * 
 * Contributors:
 *     Fraunhofer IGD <http://www.igd.fraunhofer.de/>
 */

package de.fhg.igd.mapviewer.cache;

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import org.apache.commons.io.IOUtils;
import org.jdesktop.swingx.mapviewer.AbstractBufferedImageTileCache;
import org.jdesktop.swingx.mapviewer.TileInfo;

import de.fhg.igd.slf4jplus.ALogger;
import de.fhg.igd.slf4jplus.ALoggerFactory;

/**
 * {@link SoftTileCache} that additionally stores remote images on the local
 * file system
 * 
 * @author Simon Templer
 */
public class FileTileCache extends SoftTileCache {

    private static final ALogger log = ALoggerFactory.getLogger(FileTileCache.class);

    private final File cacheDir;

    /**
     * Constructor
     * 
     * @param cacheDir the cache directory
     */
    public FileTileCache(File cacheDir) {
        super();
        this.cacheDir = cacheDir;

        log.info("Create file tile cache with cache directory " + cacheDir.getAbsolutePath()); //$NON-NLS-1$
    }

    /**
     * @see SoftTileCache#doGet(TileInfo)
     */
    @Override
    protected BufferedImage doGet(TileInfo tile) {
        BufferedImage img = super.doGet(tile);

        if (img == null && useFileCacheFor(tile.getIdentifier())) {
            // try loading the image from local file cache
            File file = getLocalFile(tile);
            if (file.exists()) {
                try {
                    img = load(tile, new FileInputStream(file));
                } catch (FileNotFoundException e) {
                    // ignore
                } /*
                    * catch (IOException e) { log.error(
                    * "Error loading local cache file: " +
                    * file.getAbsolutePath(), e); //$NON-NLS-1$ }
                    */
            }
        }

        return img;
    }

    /**
     * @see AbstractBufferedImageTileCache#load(TileInfo)
     */
    @Override
    protected BufferedImage load(TileInfo tile) {
        try {
            return load(tile, true);
        } catch (Exception e) {
            log.error("Error loading tile", e);
            return null;
        }
    }

    private BufferedImage load(TileInfo tile, boolean cache) throws IOException {
        InputStream in = null;
        if (cache && useFileCacheFor(tile.getIdentifier())) {
            // copy to local file, load from there
            File local = getLocalFile(tile);
            if (local != null) {
                // copy stream
                local.getParentFile().mkdirs();
                local.createNewFile();

                InputStream remote = openInputStream(tile.getURI());
                FileOutputStream out = new FileOutputStream(local);
                try {
                    IOUtils.copy(remote, out);
                } finally {
                    out.close();
                    remote.close();
                }

                // use local file as new source
                in = new FileInputStream(local);
            }
        }

        if (in == null) {
            in = openInputStream(tile.getURI());
        }

        // super.load closes in
        return super.load(tile, in);
    }

    /**
     * Get the local cache file name for the given URI
     * 
     * @param tile the tile info
     * 
     * @return the local file or <code>null</code>
     */
    protected File getLocalFile(TileInfo tile) {
        URI uri = tile.getIdentifier();
        File dir = new File(cacheDir, uri.getHost());
        dir = new File(dir, "level-" + tile.getZoom()); //$NON-NLS-1$
        try {
            String mapKey = computeHash(uri.toString());
            return new File(dir, tile.getX() + "_" + tile.getY() + "_" + mapKey); //$NON-NLS-1$ //$NON-NLS-2$
        } catch (Throwable e) {
            log.error("Error determinating local file name for caching", e); //$NON-NLS-1$
            return null;
        }
    }

    /**
     * Compute a secure hash for the given string
     * 
     * @param password the string
     * 
     * @return the hash of the string as HEX string
     * @throws NoSuchAlgorithmException if the SHA-1 algorithm could not be
     *             found
     */
    protected String computeHash(String password) throws NoSuchAlgorithmException {
        MessageDigest digest = MessageDigest.getInstance("SHA-1");
        digest.reset();
        digest.update(password.getBytes());
        return byteArrayToHexString(digest.digest());
    }

    /**
     * Convert a byte array to a HEX string
     * 
     * @param bytes the byte array
     * 
     * @return the bytes as HEX string
     */
    private String byteArrayToHexString(byte[] bytes) {
        StringBuilder sb = new StringBuilder(bytes.length * 2);
        for (int i = 0; i < bytes.length; i++) {
            int v = bytes[i] & 0xff;
            if (v < 16) {
                sb.append('0');
            }
            sb.append(Integer.toHexString(v));
        }
        return sb.toString().toUpperCase();
    }

    /**
     * Determines if for a given URI the local file cache shall be used
     * 
     * @param uri the URI
     * 
     * @return if the file cache shall be used
     */
    protected boolean useFileCacheFor(URI uri) {
        String scheme = uri.getScheme();
        return scheme.equalsIgnoreCase("http") || scheme.equalsIgnoreCase("https"); //$NON-NLS-1$ //$NON-NLS-2$
    }

}