点击支付在js中处理请求：
var callbackUrl = 'http://www.xxxxx.com/reader/charges.html?uid='+localUser.id+"&price="+price;
window.location.href = callbackUrl;
ajax提交请求：
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>微信充值中...</title>
</head>
<body>

</body>
<script src="javascripts/config.js" type="text/javascript"></script>
<script src="javascripts/md5.min.js"></script>
<script src="javascripts/jquery-3.2.1.min.js"></script>
<script src="javascripts/util.js"></script>
<script>

    var uid = getQueryString('uid');
    var price = getQueryString('price');
    $.ajax({
        type: 'post',
        url: '/reader/wxpay/wxCharges.dom',
        data: {uid:uid,price:price},
        success: function (data) {
　　　　　　　//后台返回调起微信支付的链接，直接跳转过去即可
            window.location.href=data;
        }
    })

    function getQueryString(name) {
        var reg = new RegExp("(^|&)" + name + "=([^&]*)(&|$)", "i");
        var r = window.location.search.substr(1).match(reg);
        if (r != null) {
            return unescape(r[2]);
        }
        return null;
    }

</script>

</html>

后台处理请求：

 

public String wxCharges(String price,String uid) {

        try{
            logger.info("before insert charge...");
            Charge charge = new Charge();
            charge.setId(IdGenerate.getId());
            charge.setCdate(sdf.format(new Date()));
            charge.setCoin(price);
            charge.setStatus("0");
            charge.setMoney(String.valueOf(Integer.valueOf(price)/100));
            charge.setUid(uid);
            charge.setZhifutype("wx");
            charge.setXstype("web");
            chargeMapper.insertCharge(charge);
            logger.info("after insert charge...");


            //订单号
            String tradeNo = charge.getId();

            String payUrl = "https://api.mch.weixin.qq.com/pay/unifiedorder";
            String ip = SpringUtils.getRequestIP();
            System.out.println("ip:"+ip);
            String stringA = "appid="+WxPayParam.APPID+"&attach=XXXX在线充值&body=xxxx在线充值&" +
                    "mch_id="+WxPayParam.PAY_MCH_ID+"&nonce_str=1add1a30ac87aa2db72f57a2375d8fec&notify_url=" +
                    "http://www.xxxx.com/reader/wxpay/wxChargeCallback.dom&out_trade_no=" + tradeNo +
                    "&scene_info={\"h5_info\": {\"type\":\"Wap\",\"wap_url\": \"http://www.xxxx.com/reader/home.html\",\"wap_name\": \"xxxx在线充值\"}}&spbill_create_ip=" + ip + "&total_fee=" + price +"&trade_type=MWEB&key=" + WxPayParam.API_KEY;
            System.out.println(stringA);
            String sign = DigestUtils.md5Hex(stringA).toUpperCase();
//            String sign = MD5(stringA).toUpperCase();
            String xml = "<xml>\n" +
                    "    <appid>"+WxPayParam.APPID+"</appid>\n" +
                    "    <attach>xxxx在线充值</attach>\n" +
                    "    <body>xxxx在线充值</body>\n" +
                    "    <mch_id>"+WxPayParam.PAY_MCH_ID+"</mch_id>\n" +
                    "    <nonce_str>1add1a30ac87aa2db72f57a2375d8fec</nonce_str>\n" +
                    "    <notify_url>http://www.xxxx.com/reader/wxpay/wxChargeCallback.dom</notify_url>\n" +
                    "    <out_trade_no>" + tradeNo + "</out_trade_no>\n" +
                    "    <spbill_create_ip>" + ip + "</spbill_create_ip>\n" +
                    "    <total_fee>" + price + "</total_fee>\n" +
                    "    <trade_type>MWEB</trade_type>\n" +
                    "    <scene_info>{\"h5_info\": {\"type\":\"Wap\",\"wap_url\": \"http://www.xxxx.com/reader/home.html\",\"wap_name\": \"xxxx在线充值\"}}</scene_info>\n" +
                    "    <sign>" + sign + "</sign>\n" +
                    " </xml>";
            System.out.println(xml);
            HttpClient client = new HttpClient();
            client.getParams().setContentCharset("utf-8");
            PostMethod post1 = new PostMethod(payUrl);
            post1.setRequestBody(xml);
            post1.addRequestHeader("accept", "application/xml");  // 视具体情况而定，可以从浏览器或postman查看下请求的header
            post1.getParams().setParameter(HttpMethodParams.HTTP_CONTENT_CHARSET,"utf-8"); //这里设置具体编码，视具体接口而定
            post1.setRequestHeader("Content-type", "text/xml; charset=UTF-8");
            client.executeMethod(post1);
            String response1 = post1.getResponseBodyAsString();
            logger.info("response1: " + response1);
            String str=response1.substring(response1.indexOf("<mweb_url><![CDATA[")+"<mweb_url><![CDATA[".length(),response1.indexOf("]]></mweb_url>"));

　　　　　　　//redirect_url是支付成功之后你自己想要跳转的页面，默认是没有的，需要自己添加，如果不添加，支付完之后还会回到支付页面，一直循环

　　　　　　　return (str +"&redirect_url=http://www.xxxxx.com/reader/home.html");
　　　　} catch (Exception e){
　　　　　　　　logger.error("error: ", e); 
　　　　　　　　return null; 
　　　　}
 }

　　微信支付回调：

public String wxChargeCallback() {
        logger.info("wx charge call back...");
        try {
            Map<String, String> map = getWxCallbackParams();
            String result_code = map.get("result_code");
            String out_trade_no = map.get("out_trade_no");
            String total_fee = map.get("total_fee");
            logger.info("result_code: " + result_code);
            logger.info("out_trade_no: " + out_trade_no);
            logger.info("total_fee: " + total_fee);
            //处理业务逻辑
            if ("SUCCESS".equals(result_code)) {
                //微信支付成功，设置支付金额
                Charge charge = new Charge();
                charge.setId(out_trade_no);
                List<Charge> charges = chargeMapper.selectCharge(charge);

                if (charges.size() > 0) {
                    Charge c = charges.get(0);
                    logger.info(c);
                    //实际支付金额（元）
                    logger.info("before callback update charge");
                    c.setStatus("1");
                    chargeMapper.updateCharge(c);
                    logger.info("after callback update charge");

                    //更新用户币量
                    logger.info("before callback update user");
                    User user = new User();
                    user.setId(c.getUid());
                    List<User> users = userMapper.selectUser(user);
                    if (users.size() > 0) {
                        User user1 = users.get(0);
                        logger.info(user1);
                        user1.setBalance("" + (Integer.parseInt(user1.getBalance()) + Integer.parseInt(c.getCoin())));
                        userMapper.updateUser(user1);
                    }
                    logger.info("after callback update user");
                }

                return returnXML(result_code);
            }
            return returnXML("FAIL");
        } catch (Exception e) {
            e.printStackTrace();
            return returnXML("FAIL");
        }
    }

　　

    /**
     * 获取微信回调参数
     */
    private Map getWxCallbackParams() throws IOException, JDOMException {
        HttpServletRequest request = SpringUtils.getRequest();
        BufferedReader reader;
        reader = request.getReader();
        String line;
        String xmlString;
        StringBuffer inputString = new StringBuffer();

        while ((line = reader.readLine()) != null) {
            inputString.append(line);
        }
        xmlString = inputString.toString();
        request.getReader().close();
        logger.info("微信回调数据：" + xmlString);
        return XmlUtils.doXMLParse(xmlString);
    }