org.grycap.gpf4med.util.NamingUtils.java Source code

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Here is the source code for org.grycap.gpf4med.util.NamingUtils.java

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/*
 * Copyright 2013 Institute for Molecular Imaging Instrumentation (I3M)
 * 
 * Licensed under the EUPL, Version 1.1 or - as soon they will be approved by 
 * the European Commission - subsequent versions of the EUPL (the "Licence");
 * You may not use this work except in compliance with the Licence.
 * You may obtain a copy of the Licence at:
 * 
 *   http://ec.europa.eu/idabc/eupl
 * 
 * Unless required by applicable law or agreed to in writing, software 
 * distributed under the Licence is distributed on an "AS IS" basis,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing permissions and 
 * limitations under the Licence.
 * 
 * This product combines work with different licenses. See the "NOTICE" text
 * file for details on the various modules and licenses.
 * The "NOTICE" text file is part of the distribution. Any derivative works
 * that you distribute must include a readable copy of the "NOTICE" text file.
 */

package org.grycap.gpf4med.util;

import java.io.IOException;
import java.security.MessageDigest;
import java.util.Date;

import javax.annotation.Nullable;

import org.apache.commons.codec.binary.Base32;
import org.apache.commons.codec.binary.Base64;
import org.apache.commons.lang.StringUtils;

/**
 * Utilities to work with names.
 * @author Erik Torres <ertorser@upv.es>
 */
public final class NamingUtils {

    /**
     * Joins the tokens and dates provided as parameters, computes a digest and returns a Base64 
     * representation of the string produced that can be used to identify a cache element or to 
     * store a file in the disk.
     * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC2045</a>
     * @param tokens The list of input tokens that have to be used to compute the name.
     * @param dates The list of input dates that have to be used to compute the name.
     * @return A Base64 representation of the computed key.
     * @throws IOException is thrown if the computation of the key fails.
     */
    public static String genSafeKey(final @Nullable String[] tokens, final @Nullable Date[] dates)
            throws IOException {
        try {
            final byte[] digest = digest(tokens, dates);
            // encode with Base64
            return new String(Base64.encodeBase64(digest, false, false));
        } catch (Exception e) {
            throw new IOException("Key generation has failed", e);
        }
    }

    /**
     * Joins the tokens and dates provided as parameters, computes a digest and returns a Base32 
     * representation of the string produced that can be used to identify a cache element. The 
     * generated key will only contain the characters A-Z and 2-7.
     * @see <a href="http://www.ietf.org/rfc/rfc4648.txt">RFC4648</a>
     * @param tokens The list of input tokens that have to be used to compute the key.
     * @param dates The list of input dates that have to be used to compute the key.
     * @param extension Optional file-name extension.
     * @return A Base32 representation of the computed file-name.
     * @throws IOException is thrown if the computation of the file-name fails.
     */
    public static String genSafeFilename(final @Nullable String[] tokens, final @Nullable Date[] dates,
            final @Nullable String extension) throws IOException {
        try {
            final byte[] digest = digest(tokens, dates);
            // encode with Base32
            return new Base32().encodeAsString(digest)
                    + (StringUtils.isNotBlank(extension) ? extension.trim() : "");
        } catch (Exception e) {
            throw new IOException("Filename generation has failed", e);
        }
    }

    private static byte[] digest(final @Nullable String[] tokens, @Nullable final Date[] dates) throws IOException {
        try {
            String mixName = "";
            if (tokens != null) {
                for (final String token : tokens) {
                    mixName += (token != null ? token.trim() : "");
                }
            }
            if (dates != null) {
                for (final Date date : dates) {
                    mixName += (date != null ? Long.toString(date.getTime()) : "");
                }
            }
            // compute digest
            final byte[] bytesOfMixName = mixName.getBytes("UTF-8");
            final MessageDigest md = MessageDigest.getInstance("SHA");
            return md.digest(bytesOfMixName);
        } catch (Exception e) {
            throw new IOException("Digest computation has failed", e);
        }
    }

}