ASCII 排序,signUtil，MD5，StringToMap

package Utils;

import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.SortedMap;
import java.util.TreeMap;
import com.alibaba.fastjson.JSONObject;

public class signUtil {

    /**
     * 按照字段名的ASCII 码从小到大排序,并且使用”&”作为分隔符，组成字符串
     * 对组装好的参数添加双方约好的密钥Key,进行MD5加密,并将签名都转换为小写字母
     * @param params
     * @param key
     * @return
     */
    public static JSONObject createSign(Map params, String key) {

        StringBuffer sb = new StringBuffer();
        StringBuffer sbkey = new StringBuffer();
        // entrySet 所有参与传参的参数按照accsii排序（升序）
        Set es = params.entrySet();
        Iterator it = es.iterator();

        while (it.hasNext()) {
            Map.Entry entry = (Map.Entry) it.next();
            String k = (String) entry.getKey();
            Object v = entry.getValue();
            //空值不传递，不参与签名组串
            if (null != v && !"".equals(v)) {
                sb.append(k + "=" + v + "&");
            }
        }
        JSONObject json = new JSONObject();
        json.put("sb", sb.toString());
        sbkey = sb.append("key=" + key);
        System.out.println("请求参数+key---> : "+sbkey);
        //MD5加密,结果转换为小写字符
        String sign = encode(sbkey.toString()).toLowerCase();
        json.put("sign", sign.toString());
        return json;
    }
    
    /**
     * MD5加密
     * @param str
     * @return
     */
     public static String encode(String str) {
            MessageDigest digest;
            try {
                digest = MessageDigest.getInstance("MD5");
                digest.update(str.getBytes());
                return new BigInteger(1, digest.digest()).toString(16);
            } catch (NoSuchAlgorithmException e) {
                e.printStackTrace();
                return null;
            }
        }
     
    /**
     * StringToMap
     * @param str
     * @return
     */
     public static SortedMap<Object, Object> StringToMap(String str){  
            String[] strs=str.split("&");  
            SortedMap<Object, Object> map = new  TreeMap<>();
            for (String string : strs) {  
                String key=string.split("=")[0];  
                String value=string.split("=")[1];  
                map.put(key, value);  
            }  
            return map;  
        }  
     
    public static void main(String[] args) {

        
        String key = "1234";
        SortedMap<Object, Object> map = new  TreeMap<>();
        map.put("user", "1");
        map.put("time", "2018-09-09 23:31:00");
        map.put("number", "3000000000000");
        JSONObject json = createSign(map,key);
        String sb = json.containsKey("sb")?json.getString("sb"):"";
        String sign = json.containsKey("sign")?json.getString("sign"):"";
        String url = sb+"sign="+sign;
        System.out.println("url--->  :  "+url);
        
    }
    
    
    
    
}

针对同一字符串加密结果不通的问题，需要根据运行环境指定字符集：

/**
* MD5加密
* @param str
* @return
* @throws UnsupportedEncodingException
*/
public static String encode(String str) throws UnsupportedEncodingException {
MessageDigest digest;
try {
digest = MessageDigest.getInstance("MD5");
digest.update(str.getBytes("UTF-8"));
return new BigInteger(1, digest.digest()).toString(16);
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
return null;
}
}

验证地址：http://tool.chinaz.com/Tools/md5.aspx