com.googlecode.DownloadCache.java Source code

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Here is the source code for com.googlecode.DownloadCache.java

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/**
 * Copyright 2012, Red Hat Inc.
 *
 * 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.googlecode;

import org.apache.commons.io.FileUtils;

import java.io.*;
import java.security.MessageDigest;
import java.util.HashMap;
import java.util.Map;

/**
 * A class representing a download cache
 * @author Mickael Istria (Red Hat Inc)
 *
 */
public class DownloadCache {

    private static final String INDEX_FILENAME = "index.ser";

    private File basedir;
    private File indexFile;
    private Map<String, CachedFileEntry> index;

    public DownloadCache(File cacheDirectory) {
        this.basedir = cacheDirectory;
        this.indexFile = new File(this.basedir, INDEX_FILENAME);
    }

    private CachedFileEntry getEntry(String url, String md5, String sha1) throws Exception {
        loadIndex();
        CachedFileEntry res = this.index.get(url);
        if (res == null) {
            return null;
        }
        File resFile = new File(this.basedir, res.fileName);
        if (!resFile.isFile()) {
            return null;
        }
        if (md5 != null && !md5.equals(SignatureUtils.getMD5(resFile))) {
            return null;
        }
        if (sha1 != null && !sha1.equals(SignatureUtils.getSHA1(resFile))) {
            return null;
        }
        return res;
    }

    /**
     * Get a File in the download cache. If no cache for this URL, or
     * if expected signatures don't match cached ones, returns null.
     * available in cache,
     * @param url URL of the file
     * @param md5 MD5 signature to verify file. Can be null => No check
     * @param sha1 Sha1 signature to verify file. Can be null => No check
     * @return A File when cache is found, null if no available cache
     */
    public File getArtifact(String url, String md5, String sha1) throws Exception {
        CachedFileEntry res = getEntry(url, md5, sha1);
        if (res != null) {
            return new File(this.basedir, res.fileName);
        }
        return null;
    }

    public void install(String url, File outputFile, String md5, String sha1) throws Exception {
        loadIndex();
        if (md5 == null) {
            md5 = SignatureUtils.computeSignatureAsString(outputFile, MessageDigest.getInstance("MD5"));
        }
        if (sha1 == null) {
            sha1 = SignatureUtils.computeSignatureAsString(outputFile, MessageDigest.getInstance("SHA1"));
        }
        CachedFileEntry entry = getEntry(url, md5, sha1);
        if (entry != null) {
            return; // entry already here
        }
        entry = new CachedFileEntry();
        entry.fileName = outputFile.getName();
        this.index.put(url, entry);
        FileUtils.copyFile(outputFile, new File(this.basedir, entry.fileName));
        saveIndex();
    }

    private void loadIndex() throws Exception {
        if (this.indexFile.isFile()) {
            FileInputStream input = new FileInputStream(this.indexFile);
            ObjectInputStream deserialize = new ObjectInputStream(input);
            this.index = (Map<String, CachedFileEntry>) deserialize.readObject();
            deserialize.close();
        } else {
            this.index = new HashMap<String, CachedFileEntry>();
        }

    }

    private void saveIndex() throws Exception {
        if (this.basedir.exists() && !this.basedir.isDirectory()) {
            throw new Exception("Cannot use " + this.basedir + " as cache directory: file exists");
        }
        if (!this.basedir.exists()) {
            this.basedir.mkdirs();
        }
        if (!this.indexFile.exists()) {
            this.indexFile.createNewFile();
        }
        FileOutputStream out = new FileOutputStream(this.indexFile);
        ObjectOutputStream res = new ObjectOutputStream(out);
        res.writeObject(index);
        res.close();
    }

}