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在开发微信小程序支付的功能前，我们先熟悉下微信小程序支付的业务流程图：

不熟悉流程的建议还是仔细阅读微信官方的。

一，准备工作

事先需要申请企业版小程序，并开通“微信支付”（即商户功能）。并获取一下参数：

appid=********  //小程序appidmchid=********  //小程序绑定商户idkey=*****************  //商户后台设置的key

并在商户后天设置开发者选项，主要是设置回调域名。

二，Java后台代码编写

Controller层代码：

@RestController@RequestMapping(value = "/payment/")public class PaymentController {	private static Logger logger = LoggerFactory.getLogger(PaymentController.class);	@Value("${hcc.wx.domain}")	private String orderDomain;		@Autowired	private PaymentService paymentService;     /**	 * 
统一下单入口
	 *	 * @param request	 * @param response	 * @throws Exception	 */	@ResponseBody    @RequestMapping(value="toPay", method=RequestMethod.POST, produces ={"application/json;charset=UTF-8"})	public JSONObject toPay(HttpServletRequest request) throws Exception {		String requestStr = RequestStr.getRequestStr(request);		if (StringUtils.isEmpty(requestStr)) {			throw new ParamException();		}		JSONObject jsonObj = JSONObject.parseObject(requestStr);		if(StringUtils.isEmpty(jsonObj.getString("orderNo")) || StringUtils.isEmpty(jsonObj.getString("openId"))){		   	throw new ParamException();		}	   	OrderInfo orderInfo = .....//此处写获取订单信息方法	   	if(orderInfo == null){	   		return AjaxUtil.renderFailMsg("订单不存在！");	   	}else if(orderInfo.getPayAmount() == null || orderInfo.getPayAmount() <= 0){	   		return AjaxUtil.renderFailMsg("订单有误，请确认！");	   	}else if(orderInfo.getOrderStatus() != 1){//1待付款	   		String msg = orderInfo.getOrderStatus() >1 ?"此订单已支付！":"订单未提交，请确认！";	   		return AjaxUtil.renderFailMsg(msg);	   	}else{	   		logger.info("【小程序支付服务】请求订单编号:["+orderInfo.getOrderNo()+"]");		   	Map
   
     resMap = paymentService.xcxPayment(+orderInfo.getOrderNo(),orderInfo.getPayAmount(),jsonObj.getString("openId"));		   	if("SUCCESS".equals(resMap.get("returnCode")) && "OK".equals(resMap.get("returnMsg"))){		   		//统一下单成功		   		resMap.remove("returnCode");		   		resMap.remove("returnMsg");		   		logger.info("【小程序支付服务】支付下单成功！");		   		return AjaxUtil.renderSuccessMsg(resMap);		   	}else{		   		logger.info("【小程序支付服务】支付下单失败！原因:"+resMap.get("returnMsg"));		   		return AjaxUtil.renderFailMsg(resMap.get("returnMsg"));		   }	   	}	}    /**	 * 
    
回调Api
	 *	 * @param request	 * @param response	 * @throws Exception	 */    @RequestMapping(value="xcxNotify")	public void xcxNotify(HttpServletRequest request,HttpServletResponse response) throws Exception { 		InputStream inputStream =  request.getInputStream(); 		//获取请求输入流		ByteArrayOutputStream outputStream = new ByteArrayOutputStream();        byte[] buffer = new byte[1024];        int len = 0;        while ((len=inputStream.read(buffer))!=-1){            outputStream.write(buffer,0,len);        }        outputStream.close();        inputStream.close();        Map
    
      map = BeanToMap.getMapFromXML(new String(outputStream.toByteArray(),"utf-8"));        logger.info("【小程序支付回调】 回调数据： \n"+map);        String resXml = "";        String returnCode = (String) map.get("return_code");        if ("SUCCESS".equalsIgnoreCase(returnCode)) {            String returnmsg = (String) map.get("result_code");            if("SUCCESS".equals(returnmsg)){            	//更新数据            	int result = paymentService.xcxNotify(map);            	if(result > 0){	            	//支付成功	                resXml = "
     
      " + "
      
      "	                        + "
      
      "+"
     ";            	}            }else{                resXml = "
     
      " + "
      
      "                        + "
      " + "";                logger.info("支付失败:"+resXml);            }        }else{            resXml = "" + ""                    + "
       " + "";            logger.info("【订单支付失败】");        }                logger.info("【小程序支付回调响应】 响应内容：\n"+resXml);        response.getWriter().print(resXml);	}}]]>
       
      
     
    
   

Service接口层代码（部分代码）：

/*** 
支付接口层
* * @author att  * @date 2018年5月27日* @since jdk1.8* @version 1.0 */public interface PaymentService {	Map
   
     xcxPayment(String orderNo, double money,String openId) throws Exception;		int xcxNotify(Map
    
      map) throws Exception;}
    
   

Service接口实现（部分代码）：

@Service(value = "paymentService")public class PaymentServiceImpl implements PaymentService{	private static Logger LOGGER = LoggerFactory.getLogger(PaymentServiceImpl.class);		@Value("${spring.profiles.active}")	private String PROJECT_ENV;		@Value("${hcc.wx.domain}")	private String orderDomain;		@Autowired	private PaymentRecordMapper paymentRecordMapper;	@Autowired	private PaymentNotifyMapper paymentNotifyMapper;		@Override	public Map
   
     xcxPayment(String orderNum, double money,String openId) throws Exception {		LOGGER.info("【小程序支付】 统一下单开始, 订单编号="+orderNum);		SortedMap
    
      resultMap = new TreeMap
     
      ();		//生成支付金额，开发环境处理支付金额数到0.01、0.02、0.03元		double payAmount = PayUtil.getPayAmountByEnv(PROJECT_ENV, money);		//添加或更新支付记录(参数跟进自己业务需求添加)		int flag = this.addOrUpdatePaymentRecord(orderNum, payAmount,.....);		if(flag < 0){			resultMap.put("returnCode", "FAIL");			resultMap.put("returnMsg", "此订单已支付！");			LOGGER.info("【小程序支付】 此订单已支付！");		}else if(flag == 0){			resultMap.put("returnCode", "FAIL");			resultMap.put("returnMsg", "支付记录生成或更新失败！");			LOGGER.info("【小程序支付】 支付记录生成或更新失败！");		}else{	        Map
      
        resMap = this.xcxUnifieldOrder(orderNum, PayConfig.TRADE_TYPE_JSAPI, payAmount,openId);	        if(PayConstant.SUCCESS.equals(resMap.get("return_code")) && PayConstant.SUCCESS.equals(resMap.get("result_code"))){	    		resultMap.put("appId", PayConfig.XCX_APP_ID);	    		resultMap.put("timeStamp", PayUtil.getCurrentTimeStamp());	    		resultMap.put("nonceStr", PayUtil.makeUUID(32));	    		resultMap.put("package", "prepay_id="+resMap.get("prepay_id"));	    		resultMap.put("signType", "MD5");	    		resultMap.put("sign", PayUtil.createSign(resultMap,PayConfig.XCX_KEY));	    		resultMap.put("returnCode", "SUCCESS");	    		resultMap.put("returnMsg", "OK");	    		LOGGER.info("【小程序支付】统一下单成功，返回参数:"+resultMap);	        }else{	        	resultMap.put("returnCode", resMap.get("return_code"));	    		resultMap.put("returnMsg", resMap.get("return_msg"));	    		LOGGER.info("【小程序支付】统一下单失败，失败原因:"+resMap.get("return_msg"));	        }		}		return resultMap;	}		/**	 * 小程序支付统一下单	 */	private Map
       
         xcxUnifieldOrder(String orderNum,String tradeType, double payAmount,String openid) throws Exception{    	//封装参数        SortedMap
        
          paramMap = new TreeMap
         
          (); paramMap.put("appid", PayConfig.XCX_APP_ID); paramMap.put("mch_id", PayConfig.XCX_MCH_ID); paramMap.put("nonce_str", PayUtil.makeUUID(32)); paramMap.put("body", BaseConstants.PLATFORM_COMPANY_NAME); paramMap.put("out_trade_no", orderNum); paramMap.put("total_fee", PayUtil.moneyToIntegerStr(payAmount)); paramMap.put("spbill_create_ip", PayUtil.getLocalIp()); paramMap.put("notify_url", this.getNotifyUrl()); paramMap.put("trade_type", tradeType); paramMap.put("openid",openid); paramMap.put("sign", PayUtil.createSign(paramMap,PayConfig.XCX_KEY)); //转换为xml String xmlData = PayUtil.mapToXml(paramMap); //请求微信后台，获取预支付ID String resXml = HttpUtils.postData(PayConfig.WX_PAY_UNIFIED_ORDER, xmlData); LOGGER.info("【小程序支付】 统一下单响应：\n"+resXml); return PayUtil.xmlStrToMap(resXml); } private String getNotifyUrl(){ //服务域名 return PayConfig.PRO_SERVER_DOMAIN + "/wxapp/payment/xcxNotify"; } /** * 添加或更新支付记录 */ @Override public int addOrUpdatePaymentRecord(String orderNo, double payAmount,......) throws Exception{ //写自己的添加或更新支付记录的业务代码 return 0; } @Override @Transactional(readOnly=false,rollbackFor={Exception.class}) public int xcxNotify(Map
          
            map) throws Exception{ int flag = 0; //支付订单编号 String orderNo = (String)map.get("out_trade_no"); //检验是否需要再次回调刷新数据 //TODO 微信后台回调，刷新订单支付状态等相关业务 return flag; }
          
         
        
       
      
     
    
   

PayUtil工具类：

/** * Function: 支付工具类 
 * date: 2018-01-18 
 * * @author att * @version 1.0 * @since JDK1.8 * @see */public class PayUtil {	static Logger log = LogManager.getLogger(PayUtil.class.getName());	/**	 * 获取当前机器的ip	 *	 * @return String	 */	public static String getLocalIp(){		InetAddress ia=null;		String localip = null;        try {            ia=ia.getLocalHost();            localip=ia.getHostAddress();        } catch (Exception e) {            e.printStackTrace();        }		return localip;        	}		/**	 * Map转换为 Xml	 * 	 * @param data	 * @return Xml	 * @throws Exception	 */	public static String mapToXml(SortedMap
   
     map) throws Exception {        DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();        //防止XXE攻击        documentBuilderFactory.setXIncludeAware(false);        documentBuilderFactory.setExpandEntityReferences(false);        DocumentBuilder documentBuilder= documentBuilderFactory.newDocumentBuilder();        org.w3c.dom.Document document = documentBuilder.newDocument();        org.w3c.dom.Element root = document.createElement("xml");        document.appendChild(root);        for (String key: map.keySet()) {            String value = map.get(key);            if (value == null) {                value = "";            }            value = value.trim();            org.w3c.dom.Element filed = document.createElement(key);            filed.appendChild(document.createTextNode(value));            root.appendChild(filed);        }        TransformerFactory tf = TransformerFactory.newInstance();        Transformer transformer = tf.newTransformer();        DOMSource source = new DOMSource(document);        transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");        transformer.setOutputProperty(OutputKeys.INDENT, "yes");        StringWriter writer = new StringWriter();        StreamResult result = new StreamResult(writer);        transformer.transform(source, result);        String output = writer.getBuffer().toString();        try {            writer.close();        }        catch (Exception ex) {        }        return output;    }		/**	 * 创建签名Sign	 * 	 * @param key	 * @param parameters	 * @return	 */ 	public static String createSign(SortedMap
    
      parameters,String key){          StringBuffer sb = new StringBuffer();          Set es = parameters.entrySet();        Iterator
      it = es.iterator();          while(it.hasNext()) {              Map.Entry entry = (Map.Entry)it.next();              String k = (String)entry.getKey();              if(entry.getValue() != null || !"".equals(entry.getValue())) {            	String v = String.valueOf(entry.getValue());            	if (null != v && !"".equals(v) && !"sign".equals(k) && !"key".equals(k)) {            		sb.append(k + "=" + v + "&");            	}            }          }          sb.append("key=" + key);          String sign = MD5Util.MD5Encode(sb.toString(), "UTF-8").toUpperCase();          return sign;      }    		/**	 * XML转换为Map	 * 	 * @param strXML	 * @return Map	 * @throws Exception	 */	public static Map
     
       getMapFromXML(String strXML) throws Exception {        try {            Map
      
        data = new HashMap
       
        ();            DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();            //防止XXE攻击            documentBuilderFactory.setXIncludeAware(false);            documentBuilderFactory.setExpandEntityReferences(false);            DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();            InputStream stream = new ByteArrayInputStream(strXML.getBytes("UTF-8"));            org.w3c.dom.Document doc = documentBuilder.parse(stream);            doc.getDocumentElement().normalize();            NodeList nodeList = doc.getDocumentElement().getChildNodes();            for (int idx = 0; idx < nodeList.getLength(); ++idx) {                Node node = nodeList.item(idx);                if (node.getNodeType() == Node.ELEMENT_NODE) {                    org.w3c.dom.Element element = (org.w3c.dom.Element) node;                    data.put(element.getNodeName(), element.getTextContent());                }            }            try {                stream.close();            } catch (Exception ex) {                ex.printStackTrace();            }            return data;        } catch (Exception ex) {            throw ex;        }	}    	/**	 * 生成随机数	 * 	 * @return	 */	public static String makeUUID(int len) {		return UUID.randomUUID().toString().replaceAll("-", "").substring(0, len);	}		/**     * 获取当前的Timestamp     *      * @return     */    public static String getCurrentTimeStamp() {        return Long.toString(System.currentTimeMillis()/1000);    }    /**     * 获取当前的时间     * @return     */    public static long getCurrentTimestampMs() {        return System.currentTimeMillis();    }        /**     * 生成订单号     *      * @return     */    public static String generateOrderNo() {	    	SimpleDateFormat sdf  = new SimpleDateFormat("yyMMdd");        return sdf.format(new Date())+makeUUID(16);    }	    /**	 * 获取当前工程url	 * 	 * @param request	 * @return	 */	public static String getCurrentUrl(HttpServletRequest request){		return request.getScheme() +"://" + request.getServerName()  + ":" +request.getServerPort() +request.getContextPath();	}		/**	 * Xml字符串转换为Map	 * 	 * @param xmlStr	 * @return	 */	public static Map
        
          xmlStrToMap(String xmlStr){ Map
         
           map = new HashMap
          
           (); Document doc; try { doc = DocumentHelper.parseText(xmlStr); Element root = doc.getRootElement(); List children = root.elements(); if(children != null && children.size() > 0) { for(int i = 0; i < children.size(); i++) { Element child = (Element)children.get(i); map.put(child.getName(), child.getTextTrim()); } } } catch (DocumentException e) { e.printStackTrace(); } return map; } public static String getSceneInfo(String wapUrl,String name){ Map
           
            
             > map = new HashMap
             
              >(); if(!StringUtils.isEmpty(wapUrl) && !StringUtils.isEmpty(name)){ /*{"h5_info": {"type":"Wap","wap_url": "https://pay.qq.com","wap_name": "腾讯充值"}}*/ Map
              
                childmap = new TreeMap
               
                (); childmap.put("type", "Wap"); childmap.put("wap_url",wapUrl); childmap.put("wap_name", name); map.put("h5_info", childmap); return JSON.toJSONString(map); } return null; } /** * 转换金额型到整型 * @param money * @return */ public static String moneyToIntegerStr(Double money){ BigDecimal decimal = new BigDecimal(money); int amount = decimal.multiply(new BigDecimal(100)) .setScale(0, BigDecimal.ROUND_HALF_UP).intValue(); return String.valueOf(amount); } /** * 除去数组中的空值和签名参数 * @param sArray 签名参数组 * @return 去掉空值与签名参数后的新签名参数组 */ public static Map
                
                  paraFilter(Map
                 
                   sArray) { Map
                  
                    result = new HashMap
                   
                    (); if (sArray == null || sArray.size() <= 0) { return result; } for (String key : sArray.keySet()) { String value = sArray.get(key); if (value == null || value.equals("") || key.equalsIgnoreCase("sign") || key.equalsIgnoreCase("sign_type")) { continue; } result.put(key, value); } return result; } /** * 把数组所有元素排序，并按照“参数=参数值”的模式用“&”字符拼接成字符串 * @param params 需要排序并参与字符拼接的参数组 * @return 拼接后字符串 */ public static String createLinkString(Map
                    
                      params) { List
                     
                       keys = new ArrayList
                      
                       (params.keySet()); Collections.sort(keys); String prestr = ""; for (int i = 0; i < keys.size(); i++) { String key = keys.get(i); String value = params.get(key); if (i == keys.size() - 1) {//拼接时，不包括最后一个&字符 prestr = prestr + key + "=" + value; } else { prestr = prestr + key + "=" + value + "&"; } } return prestr; } /** * 根据不同环境生成支付金额 * * @param env * @param money * @param payType * @return */ public static double getPayAmountByEnv(String env,Double money){ double pay_money = 0.01; //测试环境 if(BaseConstants.PLATFORM_ENV_DEV.equals(env)){ if(money>10000){ pay_money = 0.03; }else if(money>1000){ pay_money = 0.02; }else{ pay_money = 0.01; } return pay_money; }else{ //生成环境 return money; } }}
                      
                     
                    
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      
     
    
   

支付配置类：

/** * Function: 支付配置 
 * date: 2018-01-18 
 * * @author att * @version 1.0 * @since JDK1.8 */public class PayConfig {	//微信支付类型	//NATIVE--原生支付	//JSAPI--公众号支付-小程序支付	//MWEB--H5支付	//APP -- app支付	public static final String TRADE_TYPE_NATIVE = "NATIVE";	public static final String TRADE_TYPE_JSAPI = "JSAPI";	public static final String TRADE_TYPE_MWEB = "MWEB";	public static final String TRADE_TYPE_APP = "APP";				//小程序支付参数	public static String XCX_APP_ID;	public static String XCX_MCH_ID;	public static String XCX_KEY;		//微信支付API	public static final String WX_PAY_UNIFIED_ORDER = "https://api.mch.weixin.qq.com/pay/unifiedorder";		//参数	static{		Properties properties = new Properties();		try {			properties.load(PayConstant.class.getClassLoader().getResourceAsStream("payment_config.properties"));            //xcx            XCX_APP_ID=(String) properties.get("xcx.pay.appid");            XCX_MCH_ID=(String) properties.get("xcx.pay.mchid");            XCX_KEY=(String) properties.get("xcx.pay.key");		} catch (Exception e) {			e.printStackTrace();		}	}}

Properties配置：

##configxcx.pay.appid=wx**********xcx.pay.mchid=*****xcx.pay.key=**********

三，小程序端（获取统一下单返回参数发起支付）

在小程序端，发起支付请求到，Java后台的统一下单接口返回prepay_id等参数，然后封装调起微信的js方法：wx.requestPayment(OBJECT)，具体参考文档：

测试一把：

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