各种参与签名的参数和加密方式都检查过了，生成prepay_id是成功的，但是二次签名返给前端拉起页面的时候提示签名失败；代码如下：

map.put("appid", "xxxxxxx");//父APPid
map.put("body", "buy_course");
map.put("mch_id", "xxxxxxx");//父商户号

map.put("nonce_str", nonce_str);
map.put("notify_url", unifiedOrder.getNotify_url());
map.put("out_trade_no", unifiedOrder.getOut_trade_no());
map.put("spbill_create_ip", unifiedOrder.getSpbill_create_ip());
map.put("sub_appid", "xxxxxxx");//子商户ID
map.put("sub_mch_id", "xxxxxxx");//子

商户号

map.put("total_fee", "100");

map.put("trade_type", unifiedOrder.getTrade_type());
map.put("sub_openid", unifiedOrder.getOpenid());
System.out.print("======================openId============================"+unifiedOrder.getOpenid()+"\n");
String sign = WxPayUtils.sign(map,"xxxxxxxx");//父商户key
String xml=WXPayUtil.generateSignedXml(map,"yunqihuifuwushang7654123yunqihui");
        //微信统一订单接口
String url = "https://api.mch.weixin.qq.com/pay/unifiedorder";
            //https://api.mch.weixin.qq.com/pay/unifiedorde
//post方式访问微信统一订单接口
Map<String,String> response_map= WxPayUtils.sendPost(url, xml);
System.out.print("========================所有返回值=========================="+response_map.toString()+"\n");
System.out.print("==========================prepay_id========================"+response_map.get("prepay_id")+"\n");
System.out.print("========================nonce_str=========================="+response_map.get("nonce_str")+"\n");
Map<String,String > mapr=new HashMap<>();
mapr.put("appid", "xxxxxxx");//子商户id
mapr.put("noncestr", nonce_str);//子商户商户号

mapr.put("package", "prepay_id=" + response_map.get("prepay_id").toString());

mapr.put("partnerid", "xxxxxxxx");
mapr.put("prepayid",  response_map.get("prepay_id").toString());
mapr.put("timestamp", String.valueOf(new Date().getTime()).substring(0,10));
System.out.print("========================times=========================="+String.valueOf(new Date().getTime()).substring(0,10)+"\n");
//重新生成签名
//String poaySign=WXPayUtil.generateSignature(mapr,"yunqihuifuwushang7654123yunqihui");
String poaySign=WxPayUtils.sign(mapr,"key");//
System.out.print("========================签名=========================="+poaySign+"\n");
mapr.put("sign", poaySign);
mapr.put("signType", "MD5");