[支付]微信NATIVE扫码支付JAVA实现

步骤：

　　1.预订单

　　2.接受微信返回的url

　　3.将url转为二维码显示到页面上

　　4.扫码支付

　　5.接收微信的异步通知，在这步修改订单的状态

　　6.收到异步通知的同时给微信返回指定数据，告知对方已成功处理异步通知

难点：

　　1.根据传递的参数生成签名

　　2.将数据转为xml格式发送给微信预订单接口

常见错误：

　　1.签名错误（推荐用微信的验签工具检验）

　　2.xml格式错误（很有可能是发送数据的方式出现了问题）

具体实现：

　　1.预订单

public String getImageUrl(String body,String out_trade_no,String product_id,String total_fee) throws Exception{
        Map<String, Object> paramMap = new HashMap<String, Object>();
        paramMap.put("appid", data.getAppid()); //appid：每个公众号都有一个appid
        paramMap.put("body", body); //商品描述
        paramMap.put("mch_id", data.getMch_id()); //商户号：开通微信支付后分配
        paramMap.put("nonce_str", RandomStringGenerator.getRandomStringByLength(32));  // 随机字符串
        paramMap.put("notify_url", data.getNotify_url()); //支付成功后，回调地址
        paramMap.put("out_trade_no",  out_trade_no);  //商户订单号
        paramMap.put("product_id", product_id); // 商户根据自己业务传递的参数 当trade_type=NATIVE时必填
        paramMap.put("spbill_create_ip", this.localIp()); //本机的Ip
        paramMap.put("total_fee", total_fee); //金额必须为整数  单位为分
        paramMap.put("trade_type", data.getTrade_type()); //交易类型
        paramMap.put("sign", WxzfUtil.getSign(paramMap, WXPayAction.KEY));//根据微信签名规则，生成签名。随机参数可以在商户后台管理系统中进行设置。

        String xmlData = XmlUtils.map2xmlBody(paramMap,"xml");//把参数转换成XML数据格式
        String codeUrl = getCodeUrl(xmlData);   //获取二维码链接
        return codeUrl;
    }

public static String getSign(Map map, String key) throws Exception {
        String signTemp = "appid=" + map.get("appid") + "&body="
                + map.get("body") + "&mch_id=" + map.get("mch_id")
                + "&nonce_str=" + map.get("nonce_str") + "&notify_url="
                + map.get("notify_url") + "&out_trade_no="
                + map.get("out_trade_no") + "&product_id="
                + map.get("product_id") + "&spbill_create_ip="
                + map.get("spbill_create_ip") + "&total_fee="
                + map.get("total_fee") + "&trade_type=" + map.get("trade_type")
                + "&key=" + key;
        String sign = MD5.MD5Encode(signTemp).toUpperCase();//MD5微信接口中提供，直接调用即可
        return sign;
    }

public static String map2xmlBody(Map<String, Object> vo, String rootElement) {
        org.dom4j.Document doc = DocumentHelper.createDocument();
        Element body = DocumentHelper.createElement(rootElement);
        doc.add(body);
        __buildMap2xmlBody(body, vo);
        return doc.asXML();
    }

    @SuppressWarnings("unchecked")
    private static void __buildMap2xmlBody(Element body, Map<String, Object> vo) {
        if (vo != null) {
            Iterator<String> it = vo.keySet().iterator();
            while (it.hasNext()) {
                String key = (String) it.next();
                if (StringUtil.isNotEmpty(key)) {
                    Object obj = vo.get(key);
                    Element element = DocumentHelper.createElement(key);
                    if (obj != null) {
                        if (obj instanceof java.lang.String) {
                            element.setText((String) obj);
                        } else {
                            if (obj instanceof java.lang.Character || obj instanceof java.lang.Boolean || obj instanceof java.lang.Number
                                    || obj instanceof java.math.BigInteger || obj instanceof java.math.BigDecimal) {
                                org.dom4j.Attribute attr = DocumentHelper.createAttribute(element, "type", obj.getClass().getCanonicalName());
                                element.add(attr);
                                element.setText(String.valueOf(obj));
                            } else if (obj instanceof java.util.Map) {
                                org.dom4j.Attribute attr = DocumentHelper.createAttribute(element, "type", java.util.Map.class.getCanonicalName());
                                element.add(attr);
                                __buildMap2xmlBody(element, (Map<String, Object>) obj);
                            } else {
                            }
                        }
                    }
                    body.add(element);
                }
            }
        }
    }

/**
     * 获取一定长度的随机字符串
     * @param length 指定字符串长度
     * @return 一定长度的字符串
     */
    public static String getRandomStringByLength(int length) {
        String base = "abcdefghijklmnopqrstuvwxyz0123456789";
        Random random = new Random();
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < length; i++) {
            int number = random.nextInt(base.length());
            sb.append(base.charAt(number));
        }
        return sb.toString();
    }

//获取本机ip地址
@SuppressWarnings("rawtypes")
    private String localIp(){
         String ip = null;
         Enumeration allNetInterfaces;
         try {
             allNetInterfaces = NetworkInterface.getNetworkInterfaces();
             while (allNetInterfaces.hasMoreElements()) {
                 NetworkInterface netInterface = (NetworkInterface) allNetInterfaces.nextElement();
                 List<InterfaceAddress> InterfaceAddress = netInterface.getInterfaceAddresses();
                 for (InterfaceAddress add : InterfaceAddress) {
                     InetAddress Ip = add.getAddress();
                     if (Ip != null && Ip instanceof Inet4Address) {
                         ip = Ip.getHostAddress();
                     }
                 }
             }
         } catch (SocketException e) {
             log.warn("获取本机Ip失败:异常信息:"+e.getMessage());
         }
         return ip;
     }

　　2.接受微信返回的url

/**
     * 获取二维码链接
     * @param xmlData
     * @return
     */
    private String getCodeUrl(String xmlData) {
        String resXml = null;
        try {
            resXml = WxzfUtil.sendPost(WXPayAction.WX_CREATE_ORDER_URL, xmlData);
        } catch (UnrecoverableKeyException e1) {
            log.error(e1.getMessage());
        } catch (KeyManagementException e1) {
            log.error(e1.getMessage());
        } catch (KeyStoreException e1) {
            log.error(e1.getMessage());
        } catch (NoSuchAlgorithmException e1) {
            log.error(e1.getMessage());
        } catch (IOException e1) {
            log.error(e1.getMessage());
        }

        String code_url = "";
        Map<String, String> map;
        try {
            map = WxzfUtil.parseXml(resXml);
            Object returnCode = map.get("return_code");
            if("SUCCESS".equals(returnCode)) {
                Object resultCode = map.get("result_code");
                if("SUCCESS".equals(resultCode)) {
                    code_url = map.get("code_url").toString();
                }
            }
        } catch (Exception e) {
            log.error(e.getMessage());
            return "";
        }
        return code_url;
    }

//将xml数据发送给微信
@SuppressWarnings({ "resource" })
    public static String sendPost(String url, String postDataXML)
            throws IOException, KeyStoreException, UnrecoverableKeyException,
            NoSuchAlgorithmException, KeyManagementException {

        String result = null;

        HttpPost httpPost = new HttpPost(url);
        HttpClient client = new DefaultHttpClient();

        // 得指明使用UTF-8编码，否则到API服务器XML的中文不能被成功识别

        StringEntity postEntity = new StringEntity(postDataXML, "UTF-8");

        httpPost.addHeader("Content-Type", "text/xml");

        httpPost.setEntity(postEntity);

        try {

            HttpResponse response = client.execute(httpPost);

            HttpEntity entity = response.getEntity();

            result = EntityUtils.toString(entity, "UTF-8");

        } catch (ConnectionPoolTimeoutException e) {

            // LOG.debug("http get throw ConnectionPoolTimeoutException(wait time out)");

        } catch (ConnectTimeoutException e) {

            // LOG.debug("http get throw ConnectTimeoutException");

        } catch (SocketTimeoutException e) {

            // LOG.debug("http get throw SocketTimeoutException");

        } catch (Exception e) {

            e.printStackTrace();

            // LOG.debug("http get throw Exception" );

        } finally {
            httpPost.abort();
        }

        System.out.println(result);

        return result;

    }

　　3.将url转为二维码显示到页面上

public String payWeChat(String ids,String content,HttpServletResponse response,HttpServletRequest request, ModelMap model){
        WebErrors errors = WebErrors.create(request);
        try {
            OmShopOrder order = orderService.findById(Long.parseLong(ids));
            content = this.getImageUrl(order.getSoProductname(), order.getSoId().toString(), order.getSoId().toString(), (int)(order.getSoTotal()*10*10)+"");
            MultiFormatWriter multiFormatWriter = new MultiFormatWriter();
            Hashtable hints = new Hashtable();
            hints.put(EncodeHintType.CHARACTER_SET, "UTF-8");
            BitMatrix bitMatrix = multiFormatWriter.encode(content, BarcodeFormat.QR_CODE, 400, 400,hints);
            response.setContentType("image/jpeg");
            MatrixToImageWriter.writeToStream(bitMatrix, "jpg", response.getOutputStream());
         } catch (Exception e) {
            e.printStackTrace();
            log.warn("订单已支付，请勿重新支付");
         }
        return null;
    }

　　4.扫码支付

　　5.接收微信的异步通知，在这步修改订单的状态

if ("SUCCESS".equals(returnMap.get("return_code"))&&"SUCCESS".equals(returnMap.get("result_code"))) {
//处理你的业务逻辑代码（修改订单支付状态）
            }

　　6.收到异步通知的同时给微信返回指定数据，告知对方已成功处理异步通知

response.setContentType("text/plain;charset=UTF-8");
                PrintWriter writer;
                try {
                    writer = response.getWriter();
                    writer.write("<xml><return_code><![CDATA[SUCCESS]]></return_code><return_msg><![CDATA[OK]]></return_msg></xml>");
                    writer.flush();
                } catch (IOException e) {
                    e.printStackTrace();
                }