微信支付簽名算法

 public static String createSign(String characterEncoding,SortedMap<Object,Object> parameters){  
        StringBuffer sb = new StringBuffer();  
        Set es = parameters.entrySet();//所有參與傳參的參數按照accsii排序（升序）  
        Iterator it = es.iterator();  
        while(it.hasNext()) {  
            Map.Entry entry = (Map.Entry)it.next();  
            String k = (String)entry.getKey();  
            Object v = entry.getValue();  
            if(null != v && !"".equals(v)   
                    && !"sign".equals(k) && !"key".equals(k)) {  
                sb.append(k + "=" + v + "&");  
            }  
        }  
        sb.append("key=" + Key);  
        String sign = MD5Encode(sb.toString(), characterEncoding).toUpperCase();  
        return sign;  
    }