MD5.java

/*
 * Copyright (c) 2009-2016, b3log.org & hacpai.com
 *
 * 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 org.b3log.latke.util;


import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import org.b3log.latke.logging.Level;
import org.b3log.latke.logging.Logger;


/**
 * MD5 hash.
 *
 * @author <a href="http://88250.b3log.org">Liang Ding</a>
 * @version 1.0.0.4, Dec 3, 2010
 */
public final class MD5 {

    /**
     * Logger.
     */
    private static final Logger LOGGER = Logger.getLogger(MD5.class.getName());

    /**
     * Message digest.
     */
    private static MessageDigest messageDigest;

    /**
     * Low 8 bits all sets to 1.
     */
    private static final int LOW_8_BITS_1 = 0xff;

    /**
     * Append size.
     */
    private static final int APPEND_SIZE = 16;

    /**
     * Private default constructor.
     */
    private MD5() {}

    static {
        try {
            messageDigest = MessageDigest.getInstance("MD5");
        } catch (final NoSuchAlgorithmException e) {
            LOGGER.log(Level.ERROR, e.getMessage(), e);
            throw new RuntimeException(e);
        }
    }

    /**
     * Hashs(MD5) the specified string.
     *
     * @param string the specified string
     * @return hashed string from the specified string
     */
    public static String hash(final String string) {
        final char[] charArray = string.toCharArray();
        final byte[] byteArray = new byte[charArray.length];

        for (int i = 0; i < charArray.length; i++) {
            byteArray[i] = (byte) charArray[i];
        }

        final byte[] bytes = messageDigest.digest(byteArray);
        final StringBuffer hexValue = new StringBuffer();

        for (int i = 0; i < bytes.length; i++) {
            final int val = ((int) bytes[i]) & LOW_8_BITS_1;

            if (val < APPEND_SIZE) {
                hexValue.append("0");
            }

            hexValue.append(Integer.toHexString(val));
        }

        return hexValue.toString();
    }
}