Java WeChat native scan code payment

I. Introduction

This article introduces the steps and code examples for WeChat to initiate payment. If there are any deficiencies, please suggest and I will make corrections.

2. SDK download and install

Go to the official WeChat website to download the SDK  https://pay.weixin.qq.com/wiki/doc/api/native.php?chapter=11_1 , compile it yourself, and then introduce dependencies

<dependency>
    <groupId>com.github.wxpay</groupId>
    <artifactId>wxpay-sdk</artifactId>
    <version>0.0.3</version>
</dependency>

Three, initiate payment

HttpClientTool is a tool class I encapsulated, which can be encapsulated by itself, Google-Zxing for QR code generation 

@RequestMapping(value = "/pay", method = RequestMethod.GET)
public void pay(HttpServletResponse response) throws Exception {
    
    Map<String, String> params = new HashMap<>();
    params.put("appid", "公众号appid");
    params.put("mch_id", "商户号");
    params.put("nonce_str", WXPayUtil.generateNonceStr());
    params.put("body", "这是一笔测试订单");
    params.put("out_trade_no", WXPayUtil.generateNonceStr());
    params.put("total_fee", "10");
    params.put("spbill_create_ip", "127.0.0.1");
    params.put("notify_url", "回调地址");
    params.put("trade_type", "NATIVE");
    params.put("device_info","WEB");
    String sign = WXPayUtil.generateSignature(params, "商户key");
    params.put("sign", sign);

    //map转xml，请求微信统一下单接口，并获取微信返回结果，进行xml转map 得到codeurl
    String payXml = WXPayUtil.mapToXml(params);
    String orderStr = HttpClientTool.doPost("https://api.mch.weixin.qq.com/pay/unifiedorder", payXml, "UTF-8");

    Map<String, String> unifiedOrderMap = WXPayUtil.xmlToMap(orderStr);
    String codeUrl = unifiedOrderMap.get("code_url");

    //生成二维码并输出
    try{
        Map<EncodeHintType,Object> hints =  new HashMap<>();
        hints.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.L);
        hints.put(EncodeHintType.CHARACTER_SET,"UTF-8");
        BitMatrix bitMatrix = new MultiFormatWriter().encode(codeUrl, BarcodeFormat.QR_CODE,400,400,hints);
        OutputStream out =  response.getOutputStream();
        MatrixToImageWriter.writeToStream(bitMatrix,"png",out);
    }catch (Exception e){
        e.printStackTrace();
    }
}

Four, payment callback

When dealing with business logic, it must be able to correctly handle duplicate notifications

@RequestMapping(value = "/pay/callback")
public String orderCallback(HttpServletRequest request, HttpServletResponse response) throws Exception {
    String fail="<xml><return_code><![CDATA[FAIL]]></return_code><return_msg><![CDATA[FAIL]]></return_msg></xml>";
    String success="<xml><return_code><![CDATA[SUCCESS]]></return_code><return_msg><![CDATA[OK]]></return_msg></xml>";
    InputStream inputStream = request.getInputStream();
    BufferedReader in = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"));
    StringBuilder sb = new StringBuilder();
    String line;
    while ((line = in.readLine()) != null) {
        sb.append(line);
    }
    in.close();
    inputStream.close();
    Map<String, String> callbackMap = WXPayUtil.xmlToMap(sb.toString());
    boolean signatureValid = WXPayUtil.isSignatureValid(callbackMap, "商户key");
    if ("SUCCESS".equals(callbackMap.get("return_code")) && signatureValid == true){
        return success;
    }
    return fail;
}