java实现微信支付之扫码支付

本文直接从代码调用微信扫码支付讲起。账号配置，参数生成等请参考官方文档：https://pay.weixin.qq.com/wiki/doc/api/native.php?chapter=6_1

微信扫码支付。简单来说，就是你把微信支付需要的信息，生成到二维码图片中。通过微信扫一扫，发起支付。我们需要做的就是二件事：

一是：按照微信扫码支付规则生成二维码信息.

二是：微信没有提供生成二维码图片的接口。需要我们自己把二维码信息生成到二维码图片中。

1.模式选择：

微信扫码支付，有两种模式，文档中有介绍。第二种模式，微信接口会返回二维码信息给我们。而第一种模式则需要我们自己去生成二维码信息。会有些麻烦。尤其 是参数大小写，还有签名的问题，容易出错。总的来说第二种模式比第一种模式简单。所有我采用的是第二种模式，比较通用。京东与携程亦用的是第二种模式。

2.调用统一下单接口获取带有二维码信息的url：（模式二）

模式二的微信扫码支付，需要先调用微信的统一下单接口，生成预交易单。（参数传递与接收都是XML 数据格式。）

正确调用后，会返回含有交易标示ID，和二维码链接的URL。

3.实现扫码支付（模式二）

　　private static String APPID = "";　　

　　private static String MCHID= "";

　　private static String KEY= "";

　　private static String APPSECRET= "";

　　private static String body= "";

　　private static String notify_url= "";　　　　//回调地址。测试回调必须保证外网能访问到此地址

　  /**
　   * 统一下单接口
     * 微信二维码支付
     * @param params
     * @return
     */
    public String weixin_pay(String out_trade_no,String product_id) {
        JSONObject retJson = new JSONObject();
        try {

            String currTime = PayCommonUtil.getCurrTime();
            String strTime = currTime.substring(8, currTime.length());
            String strRandom = PayCommonUtil.buildRandom(4) + "";
            String nonce_str = strTime + strRandom;　　　　　　//生成随机字符串

            JSONObject requestObj = JSONObject.fromObject(params);

            // 正式上线的时候价格根据订单id查询
            String order_price = "1"; // 价格 注意：价格的单位是分

            SortedMap<Object, Object> packageParams = new TreeMap<Object, Object>();
            packageParams.put("appid", APPID);
            packageParams.put("mch_id", MCHID);
            packageParams.put("nonce_str", nonce_str);
            packageParams.put("body", body);
            packageParams.put("out_trade_no", out_trade_no);
            packageParams.put("total_fee", order_price);
            packageParams.put("spbill_create_ip", "用户端ip");
            packageParams.put("notify_url", notify_url);
            packageParams.put("trade_type", "NATIVE");
            packageParams.put("product_id", product_id);
            Calendar nowTime = Calendar.getInstance();
            packageParams.put("time_start", DateFormatUtil.formatDate(
                    nowTime.getTime(), "yyyyMMddHHmmss"));
            nowTime.add(Calendar.MINUTE, requestObj.getInt("expire_time"));
            packageParams.put("time_expire", DateFormatUtil.formatDate(
                    nowTime.getTime(), "yyyyMMddHHmmss"));

            String sign = PayCommonUtil.createSign("UTF-8", packageParams,
                   KEY);
            packageParams.put("sign", sign);　　　　　　　　//加密

            String requestXML = PayCommonUtil.getRequestXml(packageParams);
            logger.info("支付请求：" + requestXML);
            long startTime=System.currentTimeMillis();
            String resXml = HttpRequest.postData(
                    "https://api.mch.weixin.qq.com/pay/unifiedorder",
                    requestXML);
            long endTime=System.currentTimeMillis();

            Integer execute_time = (int) ((endTime-startTime)/1000);
            logger.info("支付结果：" + resXml);
            Map map = XMLUtil.doXMLParse(resXml);

            JSONObject reportParams = new JSONObject();
            reportParams.put("url", "https://api.mch.weixin.qq.com/pay/unifiedorder");
            reportParams.put("execute_time", execute_time);
            reportParams.put("return_code", map.get("return_code").toString());
            reportParams.put("return_msg", map.get("return_msg").toString());
            reportParams.put("result_code", map.get("result_code").toString());
            if (map.get("err_code") != null) {
                reportParams.put("err_code", map.get("err_code").toString());
                reportParams.put("err_code_des", map.get("err_code_des").toString());
            }
            reportParams.put("out_trade_no", out_trade_no);
            //交易保障
            report(reportParams.toString());
            if (map.get("return_code").toString().equals("SUCCESS") && map.get("result_code").toString().equals("SUCCESS")) {
                String urlCode = (String) map.get("code_url");　　　　　　　　　　//微信二维码短链接
                retJson.put("code", 0);
                retJson.put("message", "下单成功.");
                retJson.put("data", urlCode);
            } else {
                retJson.put("code", 1);
                retJson.put("message", map.get("err_code_des").toString());
                retJson.put("data", "");
            }
            return retJson.toString();
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }
    }

4.支付工具类

public class PayCommonUtil {

    public static Logger log = LoggerFactory.getLogger(PayCommonUtil.class);

    /**
     * 是否签名正确,规则是:按参数名称a-z排序,遇到空值的参数不参加签名。
     * @return boolean
     */
    public static boolean isTenpaySign(String characterEncoding, SortedMap<Object, Object> packageParams, String API_KEY) {
        StringBuffer sb = new StringBuffer();
        Set es = packageParams.entrySet();
        Iterator it = es.iterator();
        while(it.hasNext()) {
            Map.Entry entry = (Map.Entry)it.next();
            String k = (String)entry.getKey();
            String v = (String)entry.getValue();
            if(!"sign".equals(k) && null != v && !"".equals(v)) {
                sb.append(k + "=" + v + "&");
            }
        }  

        sb.append("key=" + API_KEY);  

        //算出摘要
        String mysign = MD5.MD5Encode(sb.toString(), characterEncoding).toLowerCase();
        String tenpaySign = ((String)packageParams.get("sign")).toLowerCase();  

        //System.out.println(tenpaySign + "    " + mysign);
        return tenpaySign.equals(mysign);
    }  

    /**
     * @author
     * @date 2016-4-22
     * @Description：sign签名
     * @param characterEncoding
     *            编码格式
     * @param parameters
     *            请求参数
     * @return
     */
    public static String createSign(String characterEncoding, SortedMap<Object, Object> packageParams, String API_KEY) {
        StringBuffer sb = new StringBuffer();
        Set es = packageParams.entrySet();
        Iterator it = es.iterator();
        while (it.hasNext()) {
            Map.Entry entry = (Map.Entry) it.next();
            String k = (String) entry.getKey();
            String v = "";
            try {
                v = (String) entry.getValue();
            } catch (Exception e) {
                // TODO: handle exception
                v = entry.getValue() + "";
            }

            if (null != v && !"".equals(v) && !"sign".equals(k) && !"key".equals(k)) {
                sb.append(k + "=" + v + "&");
            }
        }
        sb.append("key=" + API_KEY);
        String sign = MD5.MD5Encode(sb.toString(), characterEncoding).toUpperCase();
        return sign;
    }  

    /**
     * @author
     * @date 2016-4-22
     * @Description：将请求参数转换为xml格式的string
     * @param parameters
     *            请求参数
     * @return
     */
    public static String getRequestXml(SortedMap<Object, Object> parameters) {
        StringBuffer sb = new StringBuffer();
        sb.append("<xml>");
        Set es = parameters.entrySet();
        Iterator it = es.iterator();
        while (it.hasNext()) {
            Map.Entry entry = (Map.Entry) it.next();
            String k = (String) entry.getKey();
            String v = "";
            try {
                v = (String) entry.getValue();
            } catch (Exception e) {
                // TODO: handle exception
                v = entry.getValue() + "";
            }

            if ("attach".equalsIgnoreCase(k) || "body".equalsIgnoreCase(k) || "sign".equalsIgnoreCase(k)) {
                sb.append("<" + k + ">" + "<![CDATA[" + v + "]]></" + k + ">");
            } else {
                sb.append("<" + k + ">" + v + "</" + k + ">");
            }
        }
        sb.append("</xml>");
        return sb.toString();
    }  

    /**
     * 取出一个指定长度大小的随机正整数.
     *
     * @param length
     *            int 设定所取出随机数的长度。length小于11
     * @return int 返回生成的随机数。
     */
    public static int buildRandom(int length) {
        int num = 1;
        double random = Math.random();
        if (random < 0.1) {
            random = random + 0.1;
        }
        for (int i = 0; i < length; i++) {
            num = num * 10;
        }
        return (int) ((random * num));
    }  

    /**
     * 获取当前时间 yyyyMMddHHmmss
     *
     * @return String
     */
    public static String getCurrTime() {
        Date now = new Date();
        SimpleDateFormat outFormat = new SimpleDateFormat("yyyyMMddHHmmss");
        String s = outFormat.format(now);
        return s;
    }  

    public static JSONObject httpsRequestToJsonObject(String requestUrl,
            String requestMethod, String outputStr) {
        JSONObject jsonObject = null;
        try {
            StringBuffer buffer = httpsRequest(requestUrl, requestMethod,
                    outputStr);
            jsonObject = JSONObject.fromObject(buffer.toString());
        } catch (ConnectException ce) {
            log.error("连接超时：" + ce.getMessage());
        } catch (Exception e) {
            log.error("https请求异常：" + e.getMessage());
        }
        return jsonObject;
    }

    private static StringBuffer httpsRequest(String requestUrl,
            String requestMethod, String output)
            throws NoSuchAlgorithmException, NoSuchProviderException,
            KeyManagementException, MalformedURLException, IOException,
            ProtocolException, UnsupportedEncodingException {
        URL url = new URL(requestUrl);
        HttpsURLConnection connection = (HttpsURLConnection) url
                .openConnection();
        connection.setDoOutput(true);
        connection.setDoInput(true);
        connection.setUseCaches(false);
        connection.setRequestMethod(requestMethod);
        if (null != output) {
            OutputStream outputStream = connection.getOutputStream();
            outputStream.write(output.getBytes("UTF-8"));
            outputStream.close();
        }
        // 从输入流读取返回内容
        InputStream inputStream = connection.getInputStream();
        InputStreamReader inputStreamReader = new InputStreamReader(
                inputStream, "utf-8");
        BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
        String str = null;
        StringBuffer buffer = new StringBuffer();
        while ((str = bufferedReader.readLine()) != null) {
            buffer.append(str);
        }
        bufferedReader.close();
        inputStreamReader.close();
        inputStream.close();
        inputStream = null;
        connection.disconnect();
        return buffer;
    }
}