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nodejs implements WeChat code scanning payment function

小云云Original: 2018-02-22 09:00:361678browse

Preparation work

WeChat public account-appid

WeChat merchant account-mch_id

key value (required for the signature algorithm, is actually a For a 32-bit password, you can use md5 to generate one) (key setting path: WeChat Merchant Platform (pay.weixin.qq.com)-->Account Settings-->API Security-->Key Settings)

Scan QR code to pay - unified ordering

The following is WeChat mode 2 because it is simpler

  let MD5 = require(&#39;md5&#39;),
    xml2js = require(&#39;xml2js&#39;),
    url = "https://api.mch.weixin.qq.com/pay/unifiedorder",// 下单请求地址
    appid = &#39;公众号id&#39;,
    mch_id = &#39;微信商户号&#39;；
    notify_url = &#39;回调地址&#39;,
    out_trade_no = &#39;自己设置的订单号&#39;,// 微信会有自己订单号、我们自己的系统需要设置自己的订单号
    total_fee = &#39;订单金额&#39;,// 注意，单位为分
    body = &#39;商品简单描述&#39;, 
    trade_type = &#39;NATIVE&#39;,// 交易类型，JSAPI--公众号支付、NATIVE--原生扫码支付、APP--app支付
    nonce_str = moment().format(&#39;YYYYMMDDHHmmssSSS&#39;),// 随机字符串32位以下
    stringA = `appid=${公众号id}&body=${body}&mch_id=${微信商户号}&nonce_str=${nonce_str}&notify_url=${
    notify_url}&out_trade_no=${out_trade_no}&spbill_create_ip=${ctx.request.ip}&total_fee=${total_fee}&trade_type=${trade_type}`,
    stringSignTemp = stringA + "&key=xxxxxxxxxxxxxxxxx", //注：key为商户平台设置的密钥key
    sign = MD5(stringSignTemp).toUpperCase(); //注：MD5签名方式

The above are some parameters we need

For the signature generation algorithm, see WeChat official: https://pay.weixin.qq.com/wiki/doc/api/native.php?chapter=4_3

spbill_create_ip is the terminal ip address

The following splices all the parameters into xml

  const formData = "<xml>";
    formData += "<appid>" + appid + "</appid>"; //appid
    formData += "<body>" + body + "</body>"; //商品或支付单简要描述
    formData += "<mch_id>" + mch_id + "</mch_id>"; //商户号
    formData += "<nonce_str>" + nonce_str + "</nonce_str>"; //随机字符串，不长于32位
    formData += "<notify_url>" + notify_url + "</notify_url>"; //支付成功后微信服务器通过POST请求通知这个地址
    formData += "<out_trade_no>" + out_trade_no + "</out_trade_no>"; //订单号
    formData += "<total_fee>" + total_fee + "</total_fee>"; //金额
    formData += "<spbill_create_ip>" + ctx.request.ip + "</spbill_create_ip>"; //ip
    formData += "<trade_type>NATIVE</trade_type>"; //NATIVE会返回code_url ，JSAPI不会返回
    formData += "<sign>" + sign + "</sign>";
    formData += "</xml>";
  // 这里使用了egg里面请求的方式
  const resultData = yield ctx.curl(url, {
      method: &#39;POST&#39;,
      content: formData,
      headers: {
        &#39;content-type&#39;: &#39;text/html&#39;,
      },
    });

  // xml转json格式
  xml2js.parseString(resultData.data, function (err, json) {
    if (err) {
      new Error("解析xml报错")
    } else {
      var result = formMessage(json.xml); // 转换成正常的json 数据
      console.log(result) //打印出返回的结果
    }
  })
  var formMessage = function (result) {
    var message = {};
    if (typeof result === &#39;object&#39;) {
      var keys = Object.keys(result);
      for (var i = 0; i < keys.length; i++) {
        var item = result[keys[i]];
        var key = keys[i];
        if (!(item instanceof Array) || item.length === 0) {
          continue;
        }
        if (item.length === 1) {
          var val = item[0];
          if (typeof val === &#39;object&#39;) {
            message[key] = formMessage(val);
          } else {
            message[key] = (val || &#39;&#39;).trim();
          }
        } else {
          message[key] = [];
          for (var j = 0, k = item.length; j < k; j++) {
            message[key].push(formMessage(itemp[j]));
          }
        }
      }
    }
    return message;
  }

The egg request is used above Method, native node can use request

var request = require(&#39;request&#39;);
  request({
    url: url,
    method: "POST",
    body: formData
  }, function(error, response, body) {
    if (!error && response.statusCode == 200) {
    }
  });

If the request is successful, an xml will eventually be returned, and then we will parse it into json format, which will have a code_url and out_trade_no, we These two need to be returned to the front end, and then the QR code is generated and displayed to the user to scan the code to complete the payment.

Monitor whether the payment is successful

The above operations After completion, we need to know whether the user has completed the payment, because the user will stay on this page, and we need to notify the user that the payment was successful after the user has completed the payment.

First of all, when the user initiates payment, we will generate a QR code to allow the user to scan the code to pay. What we also need to do is to set up a timer and send a request every once in a while. , at this time, our node background needs to write an interface for querying orders. Previously we got out_trade_no, which is the order number inside our system. We send this data to the interface for querying orders in the background, and then the background will request after receiving it. The query interface address of WeChat is https://api.mch.weixin.qq.com/pay/orderquery. The process is the same as above, except that the interface address is different from the xml returned by WeChat. The returned fields will have a status of SUCCESS and NOTPAY, we can return it to the front end by judging whether to pay. After success, it will prompt the user that the payment is successful and close the timer.

Callback address

This is a very important part. Most operations can actually be completed above, but there are special circumstances, such as users The computer is disconnected and cannot send requests, but the mobile phone is used to pay, which will result in us not being able to record the user's payment information. At this time, the callback address is very important

Set the callback address

WeChat Merchant Center->Product Center->Development Configuration->Scan QR code After paying

, what we need to do is to use POST on the backend to receive the asynchronous callback information sent by WeChat, which is also in XML format. Note here that if receiving XML is not supported, you may get empty data

It should also be noted here that while saving the user's payment information, we must first check whether the order is paid to avoid repeated operations and the possibility of inserting multiple records

Summary

There are still pitfalls in WeChat scan code payment. If this is your first time, here is a list of things you need to pay attention to

The signature algorithm must be written correctly, otherwise it will not be successful. It must be spliced correctly.
WeChat returns data in xml format. We have to convert it to json through a plug-in, which is convenient. Obtain data
The returned code_url is used to generate a QR code for the front end, and then a timer needs to be set up to query whether the order has been paid, and finally the user is notified of the result
The callback address is very important. Our backend needs to post to receive the callback information returned by WeChat and then save the information. However, before saving the user's payment information, we need to know whether the order has been saved to avoid repeated additions. Also, the returned XML data must be ensured by the backend to be able to receive it. It cannot be received in the normal way and requires additional settings.

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