ApiSignatureUtil

package com.**.**.utils;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class ApiSignatureUtil {
    private static final char[] DIGITS_LOWER = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
    /**
     * 
     * 功能描述: <br>
     * 獲取簽名，會將paramMap裏的數據和secretKey組成name1=value1&name2=value2格式的數據後進行md5算法加簽名
     * @param appSecret 
     * @param paramMap 調用api時要傳遞參數組成的map,不可爲null
     * @return
     * @since V1.0.0
     */
    public static String getSignature(String appSecret,final Map<String, String> paramMap){
        //複製一份數據，防止源數據信息被修改
        Map<String,String> newParamMap = new HashMap<String,String>(paramMap);
        newParamMap.put("appSecret", appSecret);
        String signature = md5Hex(getSortString(newParamMap).getBytes());
        return signature;
    }
    /**
     * 
     * 功能描述: <br>
     * 獲取排序後的字符串信息
     *
     * @param paramMap 參數組成的map
     * @return
     * @since V1.0.0
     */
    private static String getSortString(Map<String, String> paramMap) {
        // 將map中的參數拼接成name=value的形式
        List<String> paramList = new ArrayList<String>(paramMap.size());
        for (String key : paramMap.keySet()) {
            String value = paramMap.get(key); 
            if(null!=value&&!value.isEmpty()){
                paramList.add(key + "=" + paramMap.get(key));
            }
        }
        // 將結果排序後拼接成name1=value1&name2=value2的形式
        Collections.sort(paramList);
        StringBuilder sb = new StringBuilder();
        for (String str : paramList) {
sb.append(str).append("&");
        }
        return sb.toString();
    }
    public static String md5Hex(byte[] data) {
        return encodeHexString(md5(data));
    }
    public static String encodeHexString(byte[] data) {
        return new String(encodeHex(data));
    }
    protected static char[] encodeHex(byte[] data) {
        char[] toDigits = DIGITS_LOWER;
        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++] = toDigits[(0xF0 & data[i]) >>> 4];
            out[j++] = toDigits[0x0F & data[i]];
        }
        return out;
    }
    public static byte[] md5(byte[] data) {
        return getMd5Digest().digest(data);
    }
    private static MessageDigest getDigest(String algorithm) {
        try {
            return MessageDigest.getInstance(algorithm);
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e.getMessage());
        }
    }
    private static MessageDigest getMd5Digest() {
        return getDigest("MD5");
    }
}