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This article mainly explains "how to dock with WeChat Pay at the back end of Java". Interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn how to dock with WeChat Pay at the back end of Java.

First of all, we need to make clear the goal. We click on WeChat Pay's official website. We mainly focus on these three payment methods, among which JSPAI and APP are mainly docking with uniapp developer WeChat Mini Programs and APP, while NATIVE is mainly docking with code-scanning payment on the web.

1. Unified preparation of three kinds of payment

It is recommended to import this jar, in which some functions that provide the interconversion between map and xml and generate signatures are very convenient to use.

Com.github.wxpay wxpay-sdk 0.0.3

Ps: all the functions under the WXPayUtil involved in the following code are from this toolkit, so don't ask where the function code is.

Callback address of merchant number and payment result notification

Callback url configuration path:

Wechat merchant platform (pay.weixin.qq.com)-- > Product Center-- > Development configuration-- > payment configuration

Since Weixin Mini Program and app are involved, their app_id is necessary.

Unified order, check, refund API address, go to the official documents to find, I wrote it directly here

/ * * Unified order issuing API * / public static final String UNIFIED_ORDER_URL = "https://api.mch.weixin.qq.com/pay/unifiedorder"; / * query order API * / public static final String ORDER_QUERY_URL =" https://api.mch.weixin.qq.com/pay/orderquery"; / * * order refund API * / public static final String ORDER_REFUND_URL = "https://api.mch.weixin.qq.com/secapi/pay/refund";"

API key

Used for signature algorithm

Access to

Wechat merchant platform (pay.weixin.qq.com)-- > account Center-- > account Settings-- > API Security-- > set API key

2.JSAPI issued the order uniformly

For the use scenario of this kind of payment, we are here WeChat Mini Programs, who is developed by docking uniapp.

We read the document carefully and extract the information. In fact, many parameters of the access interface are not required. We try our best to pay attention to the required parameters.

It is summarized as follows:

Appid WeChat Mini Programs app_idmch_id merchant number nonce_str random string, you can call the generateNonceStr method under WXPayUtil to generate sign

It can be generated by calling the generateSignature method under WXPayUtil, which needs to be encrypted with the merchant API key (APP_KEY) in preparation.

Appid WeChat Mini Programs app_idmch_id merchant number nonce_str random string, you can call the generateNonceStr method under WXPayUtil to generate sign

It can be generated by calling the generateSignature method under WXPayUtil, which needs to be encrypted with the merchant API key (APP_KEY) in preparation.

Body product description, it is recommended that the software name + product operation, such as Aixiaochu-the game recharge out_trade_no our own generated order number to ensure a unique total_fee amount under the same firm. Note that the unit is divided into spbill_create_ip user client ipnotify_url payment result notification callback address trade_type transaction type, we enter JSAPIopenid here because it is JSAPI, so must pass, openid is actually very easy to get. How to get openid from reference address

But after placing an order, how can we get the front end to call WeChat Pay? You need to check the official uniapp document WeChat Mini Programs pay here.

We found that the main thing is to get the prepaid id prepay_id and signature.

Code implementation:

Public Map unifiedOrderByJsp (Order order, String clientIp) throws Exception {long begin = System.currentTimeMillis (); / / use map to encapsulate the fixed parameter Map m = new HashMap () needed by WeChat Pay; / / set the payment parameter m.put ("appid", OrderUtils.WX_APP_ID); m.put ("mch_id", OrderUtils.MCH_ID) M.put ("nonce_str", WXPayUtil.generateNonceStr ()); / / Product description for example: Aixiaochu-Game recharge m.put ("body", "change easy -" + order.getGoodsModel () + "Buy"); / / order No. M.put ("out_trade_no", order.getOrderSn ()) M.put ("total_fee", order.getActualPrice (). Multiply (new BigDecimal). LongValue () + "); m.put (" spbill_create_ip ", clientIp); m.put (" notify_url ", OrderUtils.NOTIFY_URL); m.put (" trade_type "," JSAPI "); / / trade_type=JSAPI (i.e. JSAPI payment), openid UserThreeDao userThreeDao = new UserThreeDaoImpl () UserThree userThree = userThreeDao.queryOpenid (order.getUserId ()); if (userThree = = null) {return null;} m.put ("openid", userThree.getThreeOpenid ()); / / generate signature m.put ("sign", WXPayUtil.generateSignature (m, OrderUtils.APP_KEY)) / / send request, request path: UNIFIED_ORDER_URL = "https://api.mch.weixin.qq.com/pay/unifiedorder" HttpClient client = new HttpClient (OrderUtils.UNIFIED_ORDER_URL); / / set parameters in xml format to convert map to xml client.setXmlParam (WXPayUtil.mapToXml (m)); / / set support for https client.setHttps (true) / / send client.post () to execute the request; / / convert xml to map to accept the result Map response = WXPayUtil.xmlToMap (client.getContent ()); long end = System.currentTimeMillis (); System.out.println ("request https://api.mch.weixin.qq.com/pay/unifiedorder time: + (end-begin) +" ms ") System.out.println ("request result:" + JSON.toJSONString (response)); if ("SUCCESS" .equals (response.get ("return_code")) & & "SUCCESS" .equals (response.get ("result_code")) {Map param = new HashMap () / / the format of the returned result is https://uniapp.dcloud.io/api/plugins/payment?id=requestpayment / / random string / / timestamp, but the unit is s, not millisecond param.put ("timeStamp", String.valueOf (System.currentTimeMillis () / 1000)); param.put ("nonceStr", WXPayUtil.generateNonceStr ()) Param.put ("package", "prepay_id=" + response.get ("prepay_id")); param.put ("signType", "MD5"); param.put ("paySign", WXPayUtil.generateSignature (param, OrderUtils.APP_KEY)); return param;} / / an empty order is issued for failure return null;} 3.NATIVE

The main application scenario is code scan payment on PC.

The required parameters are summarized as follows:

Appid WeChat Mini Programs app_idmch_id merchant number nonce_str random string, you can call the generateNonceStr method under WXPayUtil to generate sign

It can be generated by calling the generateSignature method under WXPayUtil, which needs to be encrypted with the merchant API key (APP_KEY) in preparation.

Body product description, it is recommended that the software name + product operation, such as Aixiaochu-recharge the game out_trade_no the order number generated by ourselves, to ensure the unique total_fee amount under the same firm. Note that the unit is divided into spbill_create_ip user client ipnotify_url payment result notification address trade_type transaction type. When we enter NATIVEproduct_idtrade_type=NATIVE here, this parameter must be passed. This parameter is the product ID contained in the QR code, which we can define by ourselves.

The code is as follows:

Public Map unifiedOrderByNative (Order order, String clientIp) throws Exception {long begin = System.currentTimeMillis (); / / use map to encapsulate the fixed parameter Map m = new HashMap () needed by WeChat Pay; / / 1. Set the payment parameter m.put ("appid", OrderUtils.WX_APP_ID); m.put ("mch_id", OrderUtils.MCH_ID) M.put ("nonce_str", WXPayUtil.generateNonceStr ()); / / Product description for example: Aixiaochu-Game recharge m.put ("body", "change easy -" + order.getGoodsModel () + "Buy"); / / order No. M.put ("out_trade_no", order.getOrderSn ()) M.put ("total_fee", order.getActualPrice (). Multiply (new BigDecimal). LongValue () + "); m.put (" spbill_create_ip ", clientIp); m.put (" notify_url ", OrderUtils.NOTIFY_URL); m.put (" trade_type "," NATIVE ") / / when trade_type=NATIVE, this parameter must be m.put ("product_id", order.getId ()); / / generate signature m.put ("sign", WXPayUtil.generateSignature (m, OrderUtils.APP_KEY)) / / send request, request path: UNIFIED_ORDER_URL = "https://api.mch.weixin.qq.com/pay/unifiedorder" HttpClient client = new HttpClient (OrderUtils.UNIFIED_ORDER_URL); / / set parameters in xml format to convert map to xml client.setXmlParam (WXPayUtil.mapToXml (m)); / / set support for https client.setHttps (true) / / send client.post () to execute the request; / / convert xml to map to accept the result Map response = WXPayUtil.xmlToMap (client.getContent ()); long end = System.currentTimeMillis (); System.out.println ("request https://api.mch.weixin.qq.com/pay/unifiedorder time: + (end-begin) +" ms ") System.out.println ("request result:" + JSON.toJSONString (response)); if ("SUCCESS" .equals (response.get ("return_code")) & & "SUCCESS" .equals (response.get ("result_code")) {Map param = new HashMap (); / / QR code address param.put ("code_url", response.get ("code_url")) Param.put ("order_sn", order.getOrderSn ()); param.put ("order_id", order.getId ()); param.put ("total_fee", order.getActualPrice (). Multiply (new BigDecimal ("100s)). LongValue () +"); return param;} / / empty represents order failure return null;}

The most important return result in the above code is code_url. That is, the generated payment QR code address, and then scan the code with Wechat and pay.

4.APP issued the order uniformly

The application scenario is that the APP end calls WeChat Pay to dock with the app developed by uniapp

It is summarized as follows:

AppidAPP's app_idmch_id merchant number nonce_str random string. You can call the generateNonceStr method under WXPayUtil to generate sign.

It can be generated by calling the generateSignature method under WXPayUtil, which needs to be encrypted with the merchant API key (APP_KEY) in preparation.

Body product description, it is recommended that the software name + product operation, such as Aixiaochu-recharge the game out_trade_no the order number generated by ourselves, to ensure that the total_fee amount is unique under the same firm. Note that the unit is divided into spbill_create_ip user client ipnotify_url payment result notification address trade_type transaction type, we enter APP here

But after placing an order, how can we get the front end to call WeChat Pay? Here you need to check the official uniapp document WeChat Mini Programs pay:

We can see regular ones such as appid, merchant number needs, and what is necessary is prepaid id prepayid and signature.

The code is implemented as follows:

Public Map unifiedOrderByApp (Order order, String clientIp) throws Exception {long begin = System.currentTimeMillis (); / / use map to encapsulate the fixed parameter Map m = new HashMap () needed by WeChat Pay; / / 1. Set the payment parameter m.put ("appid", OrderUtils.APP_APP_ID); m.put ("mch_id", OrderUtils.MCH_ID) M.put ("nonce_str", WXPayUtil.generateNonceStr ()); / / Product description for example: Aixiaochu-Game recharge m.put ("body", "change easy -" + order.getGoodsModel () + "Buy"); / / order No. M.put ("out_trade_no", order.getOrderSn ()) M.put ("total_fee", order.getActualPrice (). Multiply (new BigDecimal). LongValue () + "); m.put (" spbill_create_ip ", clientIp); m.put (" notify_url ", OrderUtils.NOTIFY_URL); m.put (" trade_type "," APP ") / / generate signature m.put ("sign", WXPayUtil.generateSignature (m, OrderUtils.APP_KEY)); / / send request, request path: UNIFIED_ORDER_URL = "https://api.mch.weixin.qq.com/pay/unifiedorder" HttpClient client = new HttpClient (OrderUtils.UNIFIED_ORDER_URL) / / set parameters in xml format to convert map to xml client.setXmlParam (WXPayUtil.mapToXml (m)); / / set support for https client.setHttps (true); / / send client.post () to execute request; / / convert xml to map to accept the result Map response = WXPayUtil.xmlToMap (client.getContent ()); long end = System.currentTimeMillis () System.out.println ("request https://api.mch.weixin.qq.com/pay/unifiedorder time:" + (end-begin) + "ms"); System.out.println ("request result:" + JSON.toJSONString (response)) If ("SUCCESS" .equals (response.get ("return_code")) & & "SUCCESS" .equals (response.get ("result_code")) {Map param = new HashMap (); param.put ("appid", OrderUtils.APP_APP_ID); / / random string param.put ("noncestr", WXPayUtil.generateNonceStr ()) / / fixed param.put ("package", "Sign=WXPay"); param.put ("partnerid", OrderUtils.MCH_ID); param.put ("prepayid", response.get ("prepay_id")); / / timestamp, but in s, not millisecond param.put ("timestamp", String.valueOf (System.currentTimeMillis () / 1000)) / / param.put ("package", response.get ("sign")); param.put ("sign", WXPayUtil.generateSignature (param, OrderUtils.APP_KEY)); return param;} / / empty represents order failure return null;}

Encapsulate the returned results to the front end in the format officially required by uniapp.

5. Three payment methods return results

For the above three payment methods, I did not analyze their return results in detail, because the official documents are very detailed, and we need to pay close attention to the return result of prepaid id. So post the official document, if you are interested, you can read it carefully (I will mark the important ones)

Common

Among them, APP and JSAPI should focus on prepaid id.

Native scanning payment mainly focuses on code_url.

6. Check the order

In our actual business, it is obviously not appropriate to rely too much on WeChat Pay's callback results to judge the status of the order, so it is very common to check the order ourselves. The required parameters for order checking are summarized as follows:

Appidapp_idmch_id merchant number nonce_str random string. You can call the generateNonceStr method under WXPayUtil to generate sign.

It can be generated by calling the generateSignature method under WXPayUtil, which needs to be encrypted with the merchant API key (APP_KEY) in preparation.

The order number generated by out_trade_no ourselves is guaranteed to be unique under the same firm. This order number needs to be the same as the order number that we called to issue the order uniformly at that time.

Ps: the out_trade_no here can be replaced with transaction_id, but usually we may not have transaction_id when we check the order, so we can only use our own program business order number out_trade_no to check it, because transaction_id needs the API for investigation order to get it, that is to say, this parameter can be used if we "check the order again" in the future.

The code implementation goes below:

Public Map queryOrderStatus (String orderSn) throws Exception {long beginTime = System.currentTimeMillis (); / / 1, package parameters Map m = new HashMap (); m.put ("appid", OrderUtils.APP_APP_ID); m.put ("mch_id", OrderUtils.MCH_ID); m.put ("out_trade_no", orderSn); m.put ("nonce_str", WXPayUtil.generateNonceStr ()) / / generate signature m.put ("sign", WXPayUtil.generateSignature (m, OrderUtils.APP_KEY)); / / send request, request path: UNIFIED_ORDER_URL = "https://api.mch.weixin.qq.com/pay/orderquery" HttpClient client = new HttpClient (OrderUtils.ORDER_QUERY_URL); client.setXmlParam (WXPayUtil.mapToXml (m)); client.setHttps (true) Client.post (); / / 3. Return third-party data Map result = WXPayUtil.xmlToMap (client.getContent ()); long endTime = System.currentTimeMillis (); System.out.println ("request https://api.mch.weixin.qq.com/pay/orderquery time: + (endTime-beginTime) +" ms "); System.out.println (" request result: "+ JSON.toJSONString (result)) Return result;}

The parameters of the returned result are as follows, and important ones are marked:

Generally speaking, trade_state is mainly used to judge whether the user has paid successfully so as to update the order or record the successful logistics and other business operations.

Map map = orderDao.queryOrderStatus (orderSn); if (map = = null) {return ApiResponse.createApiResponse (ApiResponse.HTTP_STATE_400_ERROR_10001, "WeChat Pay error");} / / Wechat if ("SUCCESS" .equals (map.get ("trade_state")) {/ / update orders or record successful transactions and other business operations} 7. Refund

To be concise and to the point is convenient (rnm, refund)

Important parameters

Appidapp_idmch_id merchant number nonce_str random string. You can call the generateNonceStr method under WXPayUtil to generate sign.

It can be generated by calling the generateSignature method under WXPayUtil, which needs to be encrypted with the merchant API key (APP_KEY) in preparation.

The order number generated by out_trade_no ourselves is guaranteed to be unique under the same firm. This order number needs to be the same as the order number we called to issue the order and send it to us at that time. Transaction_id and the out_trade_no above choose one of the two. The official recommendation transaction_idout_refund_no is actually similar to the principle of the order number when issuing an order uniformly. We randomly generate one ourselves. Guarantee the amount of the order that can be refunded by total_fee only under the same merchant system the amount that refund_fee actually wants to refund

The code is implemented as follows:

Public Map refundOrder (RefundTrace refundTrace, Order order) throws Exception {long begin = System.currentTimeMillis (); / / use map to encapsulate the fixed parameter Map m = new HashMap () needed by WeChat Pay; / / 1. Set the payment parameter m.put ("appid", OrderUtils.WX_APP_ID); m.put ("mch_id", OrderUtils.MCH_ID) M.put ("nonce_str", WXPayUtil.generateNonceStr ()); / WeChat Pay order number m.put ("transaction_id", order.getPayId ()); / / merchant refund order number m.put ("out_refund_no", refundTrace.getRefundSn ()) / / order amount m.put ("total_fee", order.getActualPrice (). Multiply (new BigDecimal)). LongValue () + "); / / refund amount is the actual refund amount m.put (" refund_fee ", refundTrace.getRefundAmount (). Multiply (new BigDecimal (" 100 ")). LongValue () +") / / refund reason m.put ("refund_desc", refundTrace.getRefundReason ()); m.put ("notify_url", OrderUtils.NOTIFY_URL); / / generate signature m.put ("sign", WXPayUtil.generateSignature (m, OrderUtils.APP_KEY)) Send a request, request path: ORDER_REFUND_URL = "https://api.mch.weixin.qq.com/secapi/pay/refund" String content = HttpRequestUtils.refundRequest (WXPayUtil.mapToXml (m)); / / xml is converted to map to accept the result Map response = WXPayUtil.xmlToMap (content); long end = System.currentTimeMillis () System.out.println ("request https://api.mch.weixin.qq.com/secapi/pay/refund time:" + (end-begin) + "ms"); System.out.println ("request result:" + JSON.toJSONString (response)) If ("SUCCESS" .equals (response.get ("return_code")) & & "SUCCESS" .equals (response.get ("result_code")) {Map param = new HashMap (); param.put ("refund_id", response.get ("refund_id")); param.put ("refund_fee", response.get ("refund_fee")); return param } / / empty means refund failed return null;}

Pay attention here! Because the operation involves transferring the merchant's money back to the buyer's operation, the safety factor is relatively high. The official certificate required by the refund api is called.

The ways to apply for certificates are as follows:

Wechat Merchant platform (pay.weixin.qq.com)-- > account Center-- > account Settings-- > API Security-- > apply for API Certificate

To apply for a certificate, you need to put it under the project:

Then our http request here cannot be used before, and the certificate needs to be configured.

The details of the refundRequest function used in the above code are as follows:

Public static String refundRequest (String order) throws Exception {try {KeyStore clientStore = KeyStore.getInstance ("PKCS12"); / / read the PKCS12 certificate file FileInputStream instream = new FileInputStream ("apiclient_cert.p12") stored in the project; try {/ / specify the password of PKCS12 (merchant ID) clientStore.load (instream, OrderUtils.MCH_ID.toCharArray ()) } finally {instream.close ();} SSLContext sslcontext = SSLContexts.custom (). LoadKeyMaterial (clientStore, OrderUtils.MCH_ID.toCharArray ()). Build (); / / specify TLS version SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory (sslcontext, new String [] {"TLSv1"}, null, SSLConnectionSocketFactory.getDefaultHostnameVerifier ()) / / set SSLSocketFactory CloseableHttpClient httpclient of httpclient = HttpClients.custom (). SetSSLSocketFactory (sslsf). Build (); try {HttpPost httpost = new HttpPost (OrderUtils.ORDER_REFUND_URL); / / set response header information / / httpost.addHeader ("Connection", "keep-alive"); / / httpost.addHeader ("Accept", "* / *") / / httpost.addHeader ("Content-Type", CONTENT_TYPE_FORM.toString ()); / / httpost.addHeader ("X-Requested-With", "XMLHttpRequest"); / / httpost.addHeader ("Cache-Control", "max-age=0"); / / httpost.addHeader ("User-Agent", DEFAULT_USER_AGENT) Httpost.setEntity (new StringEntity (order, "UTF-8")); CloseableHttpResponse response = httpclient.execute (httpost); try {HttpEntity entity = response.getEntity (); String jsonStr = EntityUtils.toString (response.getEntity (), "UTF-8"); EntityUtils.consume (entity) Return jsonStr;} finally {response.close ();}} finally {httpclient.close ();}} catch (Exception e) {throw new RuntimeException (e);}} 8. Supplement

The HttpClient tool class source code I use here is mainly used to send post requests with xml parameters.

Public class HttpClient {private String url; private Map param; private int statusCode; private String content; private String xmlParam; private boolean isHttps; public boolean isHttps () {return isHttps;} public void setHttps (boolean isHttps) {this.isHttps = isHttps;} public String getXmlParam () {return xmlParam;} public void setXmlParam (String xmlParam) {this.xmlParam = xmlParam } public HttpClient (String url, Map param) {this.url = url; this.param = param;} public HttpClient (String url) {this.url = url;} public void setParameter (Map map) {param = map;} public void addParameter (String key, String value) {if (param = = null) {param = new HashMap () } param.put (key, value);} public void post () throws ClientProtocolException, IOException {HttpPost http = new HttpPost (url); setEntity (http); execute (http);} public void put () throws ClientProtocolException, IOException {HttpPut http = new HttpPut (url); setEntity (http); execute (http) } public void get () throws ClientProtocolException, IOException {if (param! = null) {StringBuilder url = new StringBuilder (this.url); boolean isFirst = true; for (String key: param.keySet ()) {if (isFirst) {url.append ("?"); isFirst = false } else {url.append ("&");} url.append (key) .append ("=") .append (param.get (key));} System.out.println ("url of the request:" + url.toString ()); this.url = url.toString () } HttpGet http = new HttpGet (url); execute (http);} / * * set http post,put param * / private void setEntity (HttpEntityEnclosingRequestBase http) {if (param! = null) {List nvps = new LinkedList (); for (String key: param.keySet ()) nvps.add (new BasicNameValuePair (key, param.get (key) / / Parameter http.setEntity (new UrlEncodedFormEntity (nvps, Consts.UTF_8)); / / set parameter} if (xmlParam! = null) {http.setEntity (new StringEntity (xmlParam, Consts.UTF_8));}} private void execute (HttpUriRequest http) throws ClientProtocolException, IOException {CloseableHttpClient httpClient = null Try {if (isHttps) {SSLContext sslContext = new SSLContextBuilder () .loadTrustMaterial (null, new TrustStrategy () {/ / Trust all @ Override public boolean isTrusted (X509Certificate [] chain) String authType) throws CertificateException {return true }}). Build (); SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory (sslContext); httpClient = HttpClients.custom (). SetSSLSocketFactory (sslsf). Build ();} else {httpClient = HttpClients.createDefault () } CloseableHttpResponse response = httpClient.execute (http); try {if (response! = null) {if (response.getStatusLine ()! = null) statusCode = response.getStatusLine () .getStatusCode (); HttpEntity entity = response.getEntity () / / response content content = EntityUtils.toString (entity, Consts.UTF_8);}} finally {response.close ();}} catch (Exception e) {e.printStackTrace ();} finally {httpClient.close () }} public int getStatusCode () {return statusCode;} public String getContent () throws ParseException, IOException {return content;}} so far, I believe you have a better understanding of "how the Java backend docks WeChat Pay". You might as well do it in practice! Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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