在完成wxpay開發時，需通過MD5簽名，生成sign。

在此過程中，需對map中的key按照ASCII碼值順序進行排序，程式碼如下：

package com.yzq.te;

import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.SortedMap;
import java.util.TreeMap;

public class CreateSign {
// 微信統一下單介面路徑
private static final String UNIFORMORDER = "https://api.mch.weixin.qq.com/pay/unifiedorder";
// 微信商戶號：*****
private static final String MCHID = "1498743142";
// 微信回撥地址
private static final String NOTIFYURL = "http://139.199.115.216:8086/api/v2/wxpay/activityWxPay/activityNotify";
// 微信交易型別
private static final String TRADETYPE = "APP";
// 微信APIKEY
private static final String APIKEY = "C80056AA0C2C7321F3D62C4221D67";
// 微信APPID
private static final String APPID = "wxc5f56faced8b2";

public static void main(String[] args) {
SortedMap<Object, Object> parame = new TreeMap<Object, Object>();
parame.put("appid", APPID);
parame.put("mch_id", MCHID);// 商家賬號。
parame.put("notify_url", NOTIFYURL);// 回撥地址

StringBuffer buffer = new StringBuffer();
Set set = parame.entrySet();
Iterator iterator = set.iterator();
while (iterator.hasNext()) {
Map.Entry entry = (Map.Entry) iterator.next();
String key = (String) entry.getKey();
Object value = (String) entry.getValue();
if (null != value && !"".equals(value) && !"sign".equals(key) && !"key".equals(key)) {
buffer.append(key + "=" + value + "&");
}
}
buffer.append("key=" + APIKEY);
System.out.println(buffer);
}
}

執行結果為：

appid=wxc5f56faced8b2&mch_id=1498743142&notify_url=http://139.199.115.216:8086/api/v2/wxpay/activityWxPay/activityNotify&key=C80056AA0C2C7321F3D62C4221D67