MD5+ASCII碼遞增排序 （支付寶生成簽名的 複製及用）

package com.rs.util;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Map;
import java.util.TreeMap;


public class Md5Encrypt {
    /**
     * Used building output as Hex
     */
    private static final char[] DIGITS = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a',
            'b', 'c', 'd', 'e', 'f'};

    /**
     * 對字符串進行MD5加密
     *
     * @param text 明文
     * @return 密文
     */
    public static String md5(String text) {
        MessageDigest msgDigest = null;

        try {
            msgDigest = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            throw new IllegalStateException("System doesn't support MD5 algorithm.");
        }

        try {
            msgDigest.update(text.getBytes("UTF-8")); // 注意改接口是按照指定編碼形式簽名

        } catch (UnsupportedEncodingException e) {

            throw new IllegalStateException("System doesn't support your  EncodingException.");

        }

        byte[] bytes = msgDigest.digest();

        String md5Str = new String(encodeHex(bytes));

        return md5Str;
    }

    private static char[] encodeHex(byte[] data) {

        int l = data.length;

        char[] out = new char[l << 1];
        // two characters form the hex value.
        for (int i = 0, j = 0; i < l; i++) {
            out[j++] = DIGITS[(0xF0 & data[i]) >>> 4];
            out[j++] = DIGITS[0x0F & data[i]];
        }

        return out;
    }

    /**
     * 簽名算法
     *
     * @return
     */
    public static Object createSign(Map<String, Object> params) {
        int i = 0;
        StringBuilder sb = new StringBuilder();
        // 將參數以參數名的字典升序排序
        Map<String, Object> sortParams = new TreeMap<>(params);
        // 遍歷排序的字典,並拼接"key=value"格式
        for (Map.Entry<String, Object> entry : sortParams.entrySet()) {
            String key = entry.getKey();
            Object value = ((String) entry.getValue()).trim();
            if (null != value && !value.equals("") ) {
                if (i != 0)
                	sb.append("&");
                sb.append(key).append("=").append(value);
            }
            i++;
        }
        System.out.println(sb);
        return Md5Encrypt.md5(sb.toString() + "需要的Key");
    }
}