微信小程序支付（java后端）

微信支付文档传送门：https://pay.weixin.qq.com/wiki/doc/api/wxa/wxa_api.php?chapter=7_3

1.开发工具：
idea+springcloud+微信web开发工具

2.开发环境：
java+maven

3.开发前准备：
3.1 所需材料
小程序的appid，APPsecret，支付商户号（mch_id），商户密钥(key)，付款用户的openid。

申请接入微信商户地址：https://pay.weixin.qq.com/static/applyment_guide/applyment_detail_miniapp.shtml

3.2 开发模式
本次开发采用的开发模式是：普通模式，适用于有自己开发团队或外包开发商的直连商户收款。开发者申请自己的appid和mch_id，两者需具备绑定关系，以此来使用微信支付提供的开放接口，对用户提供服务。

开发 java

一、控制层 PaymentController.java

/**
 * 微信预支付Api
 * 统一下单接口
 * @param openId
 * @return
 */
@ApiOperation("微信预支付1")
@ApiImplicitParams({
        @ApiImplicitParam(name = "openId",value = "用户openId")
})
@PostMapping(value = {"jsapipays"})
public ResponseEntity jsapipays(@RequestParam String openId) {
    Condition usercondition = new Condition(User.class);
    usercondition.createCriteria().andEqualTo("wxId",openId);
    User user=userService.findByCondition(usercondition,null).get(0);
    //通过用户ID查询蓝牙订单
    Condition bizBluetoothOrderC=new Condition(BizBluetoothOrder.class);
    bizBluetoothOrderC.createCriteria().andEqualTo("uId",user.getId());
    List bizBluetoothOrderlist = bizBluetoothOrderService.findByCondition(bizBluetoothOrderC,null);
    if(bizBluetoothOrderlist.isEmpty()){
        return failResult("订单不存在！");
    }
    BizBluetoothOrder bizBluetoothOrder = bizBluetoothOrderlist.get(0);
    Map jsapi = wxPayService.jsapi2(bizBluetoothOrder.getOrderSn(),"18.0" ,openId);
    return successResult(jsapi);
}

二、service层

/**
 * 微信小程序支付
 * @param orderNum
 * @param openId
 * @return
 */
Map jsapi2(String orderNum , String total_fee, String openId);

三、实现类

/**
 * 统一下单开始 方法1
 * @param orderNum
 * @param total_fee
 * @param openId
 * @return
 */
@Override
public Map jsapi2(String orderNum , String total_fee, String openId) {
    try {
        log.info("订单号=="+orderNum);
        //拼接统一下单地址参数
        SortedMap paraMap = new TreeMap();
        paraMap.put("appid", WXConstEnum.appId);
        paraMap.put("body", "支付订单");
        paraMap.put("mch_id", WXConstEnum.mch_id);
        paraMap.put("nonce_str", WxPayUtils.makeUUID(32).toUpperCase());
        paraMap.put("signType",WXConstEnum.SIGNTYPE);
        paraMap.put("openid", openId);
        paraMap.put("out_trade_no",orderNum);//订单号  商户系统内部订单号，要求32个字符内，只能是数字、大小写字母_-|*且在同一个商户号下唯一
        paraMap.put("spbill_create_ip", WxPayUtils.getLocalIp());
        paraMap.put("total_fee", total_fee);
        paraMap.put("timeStamp", WxPayUtils.getCurrentTimeStamp());
        paraMap.put("trade_type",WXConstEnum.TRADETYPE);
        paraMap.put("notify_url",WXConstEnum.notify_url);// 此路径是微信服务器调用支付结果通知路径随意写
        String sign =  WXPayUtil.generateSignature(paraMap, WXConstEnum.key).toUpperCase();
        paraMap.put("sign", sign);
        String xml = WxPayUtils.mapToXml(paraMap);//将所有参数(map)转xml格式
        log.info("xml源串 = " + xml);
        // 统一下单地址 https://api.mch.weixin.qq.com/pay/unifiedorder
        String xmlStr = HttpUtils.sendPost(WXConstEnum.pay_url, xml);//发送post请求"统一下单接口"返回预支付id:prepay_id
        log.info("返回xmlStr = " + xmlStr);
        //以下内容是返回前端页面的json数据
        String prepay_id = "";//预支付id
        if (xmlStr.indexOf("SUCCESS") != -1) {
            Map map = WxPayUtils.xmlToMap(xmlStr);
            prepay_id = map.get("prepay_id");
        }
        Map payMap = new HashMap();
        payMap.put("appId", WXConstEnum.appId);
        payMap.put("timeStamp", WxPayUtils.getCurrentTimeStamp());
        payMap.put("nonceStr", WxPayUtils.makeUUID(32));
        payMap.put("signType", "MD5");
        String paySign =  WXPayUtil.generateSignature(paraMap, WXConstEnum.key).toUpperCase();
        payMap.put("paySign", paySign);
        payMap.put("package", "prepay_id=" + prepay_id);
        return payMap;
    } catch (Exception e) {
        e.printStackTrace();
    }
    return null;
}四、调用统一下单的接口 参数类WXConstEnum.java

/**
 * TODO 替换成自己的参数
 */
//微信小程序appid
public static String appId = "wx34118d54080e5555";
//微信商户号
public static String mch_id="1612911113";
//微信支付的商户密钥
public static final String key = "50c01580a2824d48a48d94e9f6b046fb";
//支付成功后的服务器回调url
public static final String notify_url="http://shopdev.lyproduct.cn/lyshop-app/app/orderapi/miniNotify";
//签名方式
public static final String SIGNTYPE = "MD5";
//交易类型
public static final String TRADETYPE = "JSAPI";
//微信统一下单接口地址
public static final String pay_url = "https://api.mch.weixin.qq.com/pay/unifiedorder";

//微信支付返回状态码
public static final String SUCCESS = "SUCCESS";

五、WxPayUtils.java 需要用到的工具类 官方文档会有提供SDK

/**
 * XML格式字符串转换为Map
 *
 * @param strXML XML字符串
 * @return XML数据转换后的Map
 * @throws Exception
 */
public static Map xmlToMap(String strXML) throws Exception {
    try {
        Map data = new HashMap();
        DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
        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) {
            // do nothing
        }
        return data;
    } catch (Exception ex) {
        throw ex;
    }

}

/**
 * 将Map转换为XML格式的字符串
 *
 * @param data Map类型数据
 * @return XML格式的字符串
 * @throws Exception
 */
public static String mapToXml(SortedMap data) 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: data.keySet()) {
        String value = data.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;
}


/**
 * 生成签名
 *
 * @param data 待签名数据
 * @param key API密钥
 * @return 签名
 */
public static String generateSignature(final Map data, String key) throws Exception {
    return generateSignature(data, key, WXPayConstants.SignType.MD5);
}

/**
 * 生成签名. 注意，若含有sign_type字段，必须和signType参数保持一致。
 *
 * @param data 待签名数据
 * @param key API密钥
 * @param signType 签名方式
 * @return 签名
 */
public static String generateSignature(final Map data, String key, WXPayConstants.SignType signType) throws Exception {
    Set keySet = data.keySet();
    String[] keyArray = keySet.toArray(new String[keySet.size()]);
    Arrays.sort(keyArray);
    StringBuilder sb = new StringBuilder();
    for (String k : keyArray) {
        if (k.equals(WXPayConstants.FIELD_SIGN)) {
            continue;
        }
        if (data.get(k).trim().length() > 0) // 参数值为空，则不参与签名
            sb.append(k).append("=").append(data.get(k).trim()).append("&");
    }
    sb.append("key=").append(key);
    if (WXPayConstants.SignType.MD5.equals(signType)) {
        return MD5(sb.toString()).toUpperCase();
    }
    else if (WXPayConstants.SignType.HMACSHA256.equals(signType)) {
        return HMACSHA256(sb.toString(), key);
    }
    else {
        throw new Exception(String.format("Invalid sign_type: %s", signType));
    }
}
/**
 * 生成 MD5
 *
 * @param data 待处理数据
 * @return MD5结果
 */
public static String MD5(String data) throws Exception {
    MessageDigest md = MessageDigest.getInstance("MD5");
    byte[] array = md.digest(data.getBytes("UTF-8"));
    StringBuilder sb = new StringBuilder();
    for (byte item : array) {
        sb.append(Integer.toHexString((item & 0xFF) | 0x100).substring(1, 3));
    }
    return sb.toString().toUpperCase();
}

/**
 * 生成 HMACSHA256
 * @param data 待处理数据
 * @param key 密钥
 * @return 加密结果
 * @throws Exception
 */
public static String HMACSHA256(String data, String key) throws Exception {
    Mac sha256_HMAC = Mac.getInstance("HmacSHA256");
    SecretKeySpec secret_key = new SecretKeySpec(key.getBytes("UTF-8"), "HmacSHA256");
    sha256_HMAC.init(secret_key);
    byte[] array = sha256_HMAC.doFinal(data.getBytes("UTF-8"));
    StringBuilder sb = new StringBuilder();
    for (byte item : array) {
        sb.append(Integer.toHexString((item & 0xFF) | 0x100).substring(1, 3));
    }
    return sb.toString().toUpperCase();
}





/**
 * 获取有序map
 * @param map
 * @return
 */
public static SortedMap getSortedMap(Map map){

    SortedMap sortedMap = new TreeMap<>();
    Iterator it =  map.keySet().iterator();
    while (it.hasNext()){
        String key  = (String)it.next();
        String value = map.get(key);
        String temp = "";
        if( null != value){
            temp = value.trim();
        }
        sortedMap.put(key,temp);
    }
    return sortedMap;
}

/**
 * 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();
}
/**
 * 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;

}

/**
 * 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);
}

/**
 * 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();
}

/**
 * 转换double 为 int string
 * @param payAmount
 * @return
 */
public static String moneyToIntegerStr(double payAmount){
    String money = String.valueOf(payAmount);
    return money;
}

传递的xml参数必须按照官方接口文档（https://pay.weixin.qq.com/wiki/doc/api/wxa/wxa_api.php?chapter=9_1），如果出现sing签名错误的问题，试试修改商户密钥(本人修改了三次才成功)。

control层调用接口时 我是值传递了openId 可以根据下单的需要去其他参数（注意大小写）

所有的参数都有，应该不会看不懂吧。直接复制粘贴！