使用MD5對字符串加密

package com.iwhalecloud.retail.enterprise.c.utils;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class MD5Util {
    //將字節數組轉成十六進制字符串
    private static String byteArrayToHexString(byte b[]) {
        StringBuffer resultSb = new StringBuffer();
        for (int i = 0; i < b.length; i++)
            resultSb.append(byteToHexString(b[i]));

        return resultSb.toString();
    }

    //對單個字節轉換成整數進行取商取余數計算
    private static String byteToHexString(byte b) {
        int n = b;
        if (n < 0)
            n += 256;
        int d1 = n / 16;
        int d2 = n % 16;
        //根據下標d1，d2去數組hexDigits的數據
        return hexDigits[d1] + hexDigits[d2];
    }

    public static String MD5Encode(String origin, String charsetname) {
        String resultString = null;
        try {
            resultString = new String(origin);
            // 獲得MD5摘要算法的 MessageDigest 對象
            MessageDigest md = MessageDigest.getInstance("MD5");
            if (charsetname == null || "".equals(charsetname))
                //將加密之后的字節數據轉換成16進制的字符串
                resultString = byteArrayToHexString(md.digest(resultString
                        .getBytes()));
            else
                resultString = byteArrayToHexString(md.digest(resultString
                        .getBytes(charsetname)));
        } catch (Exception exception) {
        }
        return resultString;
    }

    private static final String hexDigits[] = {"0", "1", "2", "3", "4", "5",
            "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};
    /**
     * MD5加密字符串（32位大寫）
     *
     * @param string 需要進行MD5加密的字符串
     * @return 加密后的字符串（大寫）
     */
    public static String md5Encrypt32Upper(String string) {
        byte[] hash;
        try {
            //創建一個MD5算法對象，並獲得MD5字節數組,16*8=128位
            hash = MessageDigest.getInstance("MD5").digest(string.getBytes("UTF-8"));
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("Huh, MD5 should be supported?", e);
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException("Huh, UTF-8 should be supported?", e);
        }

        //轉換為十六進制字符串
        StringBuilder hex = new StringBuilder(hash.length * 2);
        for (byte b : hash) {
            if ((b & 0xFF) < 0x10) hex.append("0");
            hex.append(Integer.toHexString(b & 0xFF));
        }
        return hex.toString().toUpperCase();
    }

    /**
     * MD5加密字符串（32位小寫）
     *
     * @param string 需要進行MD5加密的字符串
     * @return 加密后的字符串（小寫）
     */
    public static String md5Encrypt32Lower(String string) {
        //直接上面的方法轉換成小寫就可以了
        return md5Encrypt32Upper(string).toLowerCase();
    }

    /**
     * 將二進制字節數組轉換為十六進制字符串
     *
     * @param bytes 二進制字節數組
     * @return 十六進制字符串
     */
    public static String bytesToHex(byte[] bytes) {
        StringBuffer hexStr = new StringBuffer();
        int num;
        for (int i = 0; i < bytes.length; i++) {
            num = bytes[i];
            if (num < 0) {
                num += 256;
            }
            if (num < 16) {
                hexStr.append("0");
            }
            hexStr.append(Integer.toHexString(num));
        }
        return hexStr.toString().toUpperCase();
    }

    /**
     * Unicode中文編碼轉換成字符串
     */
    public static String unicodeToString(String str) {
        Pattern pattern = Pattern.compile("(\\\\u(\\p{XDigit}{4}))");
        Matcher matcher = pattern.matcher(str);
        char ch;
        while (matcher.find()) {
            ch = (char) Integer.parseInt(matcher.group(2), 16);
            str = str.replace(matcher.group(1), ch + "");
        }
        return str;
    }

    public static void main(String[] args) {
        System.out.println(md5Encrypt32Lower("123456"));
        System.out.println(md5Encrypt32Upper("123456"));
    }
}