小程序微信支付 + Java后台 详解

第一次做微信支付，遇到了不少坑在这里记录一下，如有不足请大家多指教

微信支付对商户开放的所有面对用户使用的api，都是由appid和mch_id(商户号)成对使用的。

SDK下载地址 》https://pay.weixin.qq.com/wiki/doc/api/jsapi.php?chapter=11_1

大致流程

第一步：小程序端获取到js_code，然后传递到后台，后台请求微信接口 https://api.weixin.qq.com/sns/jscode2session 获取到openid(是表示用户在你的当前应用中的唯一标识这个参数很重要)

获取js_code微信api链接 》https://developers.weixin.qq.com/miniprogram/dev/api/open-api/login/wx.login.html

第二步：通过appid,mch_id,openid等一系列参数生成第一次签名然后请求微信的统一下单接口。(ps统一下单接口请求成功后返回数据给小程序时还要生成第二次签名,此处有坑兄弟们小心,第一次签名是appid是全部小写，第二次签名时appId是驼峰式！！)

统一下单接口api链接 》https://pay.weixin.qq.com/wiki/doc/api/wxa/wxa_api.php?chapter=9_1

微信签名算法链接 》https://pay.weixin.qq.com/wiki/doc/api/wxa/wxa_api.php?chapter=4_3

第三步：生成二次签名返回支付信息给小程序，获取统一下单接口成功返回的 prepay_id(预支付交易会话标识),nonce_str(随机字符串，必须使用统一下单接口返回的)，timeStamp(时间戳需要转成字符串)等参数生成签名，具体看下面代码。

第四步：小程序拿到后台返回的预支付信息去请求wx.requestPayment接口拉起小程序支付页面并完成支付。

Controller层

import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import io.swagger.annotations.ApiParam;
import org.perf4j.aop.Profiled;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import javax.servlet.http.HttpServletRequest;


/**
 * @Author LK
 * @Date 2019/7/24
 * @Time 18:32
 */
@Api(value = "WXPay", description = "小程序微信支付")
@RestController
@RequestMapping("/wx")
public class WXPayController{

    public static final Logger LOGGER = LoggerFactory.getLogger(WXPayController.class);

    @Autowired
    private WeixinService weixinService;

    /**
     * 业主微信支付
     * @param inputWXPayVO
     * @return
     */
    @ApiOperation(value = "业主微信支付")
    @PostMapping("/pay")
    public Result wxPay(@RequestBody InputWXPayVO inputWXPayVO, HttpServletRequest request) {
        return weixinService.pay(inputWXPayVO, request);
    }
}

service 层

import javax.servlet.http.HttpServletRequest;


/**
 * @Author LK
 * @Date 2019/7/24
 * @Time 18:35
 */
public interface WeixinService {

    Result pay(InputWXPayVO inputWXPayVO, HttpServletRequest request);

}

impl层

import com.jzez.b2b.config.WechatConfig;
import com.jzez.b2b.service.weixin.WeixinService;
import com.jzez.b2b.util.PayUtil;
import com.jzez.b2b.vo.input.weixin.InputWXPayVO;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.util.EntityUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Service;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

/**
 * @Author LK
 * @Date 2019/7/24
 * @Time 18:37
 */

@Service
public class WeixinServiceImpl implements WeixinService {

    public static final Logger logger = LoggerFactory.getLogger(WeixinServiceImpl.class);



    @Override
    public Result pay(InputWXPayVO inputWXPayVO, HttpServletRequest request) throws GlobalException{

        String openId = null;
            //请求微信接口获取openId
            String URL = WechatConfig.OPENID_URL + inputWXPayVO.getCode();
            try {
                HttpClient client = HttpClientBuilder.create().build();
                HttpGet httpGet = new HttpGet(URL);
                HttpResponse response = client.execute(httpGet);
                if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
                    String strResult = EntityUtils.toString(response.getEntity());
                    org.json.JSONObject jsonResult = new org.json.JSONObject(strResult);
                    openId = String.valueOf(jsonResult.get("openid"));
                }
            } catch (IOException e) {
                logger.info("获取openId失败");
            }
        //调用微信支付接口
        Map map = wxPay(openId,inputWXPayVO.getTotalFee(),inputWXPayVO.getPayOrderId(), request);
        return ResultUtil.success(map);
    }

    /**
     *
     * @param openId
     * @param totalFee 支付金额 ：分
     * @param payOrderId 商户订单id
     * @param request
     * @return
     */
    public Map wxPay(String openId,String totalFee,String payOrderId,HttpServletRequest request) {
        try {
            //生成的随机字符串
            String nonce_str = PayUtil.getRandomStringByLength(32);
            //获取客户端的ip地址
            String spbill_create_ip = PayUtil.getIpAddr(request);
            //组装参数，用户生成统一下单接口的签名
            Map packageParams = new HashMap<>();
            packageParams.put("appid", WechatConfig.APPID);
            packageParams.put("mch_id", WechatConfig.MCHID);
            packageParams.put("nonce_str", nonce_str);
            packageParams.put("body", WechatConfig.BODY);
            packageParams.put("out_trade_no", payOrderId);
            packageParams.put("total_fee", totalFee);
            packageParams.put("spbill_create_ip", spbill_create_ip);
            packageParams.put("notify_url", WechatConfig.NOTIFY_URL);
            packageParams.put("trade_type", WechatConfig.TRADETYPE);
            packageParams.put("openid", openId + "");
            //MD5运算生成签名，这里是第一次签名，用于调用统一下单接口
            String sign1 = PayUtil.generateSignature(packageParams, WechatConfig.KEY, WechatConfig.SIGNTYPE).toUpperCase();
            packageParams.put("sign",sign1);
            //map转成统一下单接口参数需要xml数据
            String xml = PayUtil.mapToXml(packageParams);
            //调用统一下单接口，并接受返回的结果
            logger.info("-----------------------开始请求微信预支付-------------------------");
            String result = PayUtil.httpRequest(WechatConfig.PAY_URL,xml);
            //将返回参数转为map
            Map map = PayUtil.xmlToMap(result);
            String return_code = (String) map.get("return_code");
            String result_code = (String) map.get("result_code");
            logger.info("-----------------------请求微信预支付结束--------------------------");
            //返回给小程序端需要的参数
            Map response = new HashMap<>();
            if (WechatConfig.SUCCESS.equals(return_code) && return_code.equals(result_code)) {
                //组装生成二次签名的参数
                //第一次生成签名时appid全部小写，此处appId必须使用驼峰式，要不然小程序支付时会报签名验证失败
                response.put("appId", WechatConfig.APPID);
                String prepay_id = String.valueOf(map.get("prepay_id"));
                response.put("nonceStr",String.valueOf(map.get("nonce_str")));
                response.put("package","prepay_id=" + prepay_id);
                //这边要将返回的时间戳转化成字符串，不然小程序端调用wx.requestPayment方法会报签名错误
                Long timeStamp = System.currentTimeMillis()/1000;
                response.put("timeStamp",String.valueOf(timeStamp));
                response.put("signType", WechatConfig.SIGNTYPE);
                //再次签名，这个签名用于小程序端调用wx.requesetPayment方法
                String sign2 = PayUtil.generateSignature(response, WechatConfig.KEY, WechatConfig.SIGNTYPE).toUpperCase();
                //加入签名返回给小程序
                response.put("paySign", sign2);
            }
            return response;
        } catch (Exception e) {
            logger.info("请求微信预支付失败");
        }
        return null;
    }

}

实体类

import io.swagger.annotations.ApiModelProperty;

/**
 * @Author LK
 * @Date 2019/7/25
 * @Time 14:43
 */
public class InputWXPayVO {

    @ApiModelProperty(value = "js_code")
    private String code;

    @ApiModelProperty(value = "付款金额：分")
    private String totalFee;

    @ApiModelProperty(value = "商家订单id")
    private String payOrderId;

    public String getCode() {
        return code;
    }
    public void setCode(String code) {
        this.code = code;
    }
    public String getTotalFee() {
        return totalFee;
    }
    public void setTotalFee(String totalFee) {
        this.totalFee = totalFee;
    }
    public String getPayOrderId() {
        return payOrderId;
    }
    public void setPayOrderId(String payOrderId) {
        this.payOrderId = payOrderId;
    }
}

常量类

/**
 * @Author LK
 * @Date 2019/7/25
 * @Time 11:33
 */
public class WechatConfig {

    //微信小程序密钥
    public static final String SECRET = "bca7fe5******************5b31f";
    //小程序appid  开发者自己拥有的
    public static final String APPID = "wx16**********56f";
    //grant_type
    public static final String GRANT_TYPE = "authorization_code";
    //微信支付的商户号
    public static final String MCHID = "12345678900";
    //微信支付的商户密钥
    public static final String KEY = "591***************************giv";
    //支付成功后的服务器回调url，这里填PayController里的回调函数地址必须是公网地址
    public static final String NOTIFY_URL = "http://abc.natappfree.cc/wx/callback";
    //签名方式，固定值
    public static final String SIGNTYPE = "MD5";

    public static final String BODY = "商品的描述信息";
    //交易类型，小程序支付的固定值为JSAPI
    public static final String TRADETYPE = "JSAPI";
    //获取openId请求地址
    public static final String OPENID_URL = "https://api.weixin.qq.com/sns/jscode2session?grant_type=" + GRANT_TYPE + "&appid=" + APPID + "&secret=" + SECRET + "&js_code=";
    //微信统一下单接口地址
    public static final String PAY_URL = "https://api.mch.weixin.qq.com/pay/unifiedorder";

    public static final String SUCCESS  = "SUCCESS";

}

工具类

import com.jzez.b2b.config.WechatConfig;
import java.io.*;
import java.security.MessageDigest;
import java.util.*;
import org.apache.commons.lang.StringUtils;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.util.EntityUtils;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import javax.servlet.http.HttpServletRequest;
import javax.xml.XMLConstants;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

/**
 * @Author LK
 * @Date 2019/7/25
 * @Time 11:17
 */
public class PayUtil {

    /**
     * 微信SDK中的生成签名方法
     * 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, String 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(WechatConfig.SIGNTYPE)) {
                continue;
            }
            if (data.get(k).trim().length() > 0){
                sb.append(k).append("=").append(data.get(k).trim()).append("&");
            }
        }
        sb.append("key=").append(key);
        if (WechatConfig.SIGNTYPE.equals(signType)) {
            return MD5(sb.toString()).toUpperCase();
        }
        else {
            throw new Exception(String.format("Invalid sign_type: %s", signType));
        }
    }

    /**
     * 生成 MD5
     * 微信SDK中的生成MD5方法
     * @param data 待处理数据
     * @return MD5结果
     */
    private static String MD5(String data) throws Exception {
        java.security.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();
    }

    /**
     * @param requestUrl    请求地址
     * @param outputStr     参数
     */
    public static String httpRequest(String requestUrl, String outputStr) {
        try {
            HttpClient httpClient = HttpClientBuilder.create().build();

            HttpPost httpPost = new HttpPost(requestUrl);
            StringEntity postEntity = new StringEntity(outputStr, "UTF-8");
            httpPost.addHeader("Content-Type", "text/xml");
            httpPost.setEntity(postEntity);

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            return EntityUtils.toString(httpEntity, "UTF-8");
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }


    /**
     * XML格式字符串转换为Map
     * 微信SDK中的方法
     * @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();
            DocumentBuilder documentBuilder = newDocumentBuilder();
            InputStream stream = new ByteArrayInputStream(strXML.getBytes("UTF-8"));
            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) {
                    Element element = (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
     * 微信SDK中的方法
     * @param data Map类型数据
     * @return XML格式的字符串
     * @throws Exception
     */
    public static String mapToXml(Map data) throws Exception {
        Document document = newDocument();
        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();
            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;
    }

    /**
     * 微信SDK中的方法
     * @return Document
     * @throws ParserConfigurationException 
     */
    private static Document newDocument() throws ParserConfigurationException {
        return newDocumentBuilder().newDocument();
    }

    /**
     * 微信SDK中的方法
     * @return DocumentBuilder
     * @throws ParserConfigurationException 
     */
    private static DocumentBuilder newDocumentBuilder() throws ParserConfigurationException {
        DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
        documentBuilderFactory.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true);
        documentBuilderFactory.setFeature("http://xml.org/sax/features/external-general-entities", false);
        documentBuilderFactory.setFeature("http://xml.org/sax/features/external-parameter-entities", false);
        documentBuilderFactory.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
        documentBuilderFactory.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true);
        documentBuilderFactory.setXIncludeAware(false);
        documentBuilderFactory.setExpandEntityReferences(false);

        return documentBuilderFactory.newDocumentBuilder();
    }

    //获取随机字符串
    public static String getRandomStringByLength(int length) {
        String base = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
        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IP
    public static String getIpAddr(HttpServletRequest request) {
        String ip = request.getHeader("X-Forwarded-For");
        if (StringUtils.isNotEmpty(ip) && !"unKnown".equalsIgnoreCase(ip)) {
            //多次反向代理后会有多个ip值，第一个ip才是真实ip
            int index = ip.indexOf(",");
            if (index != -1) {
                return ip.substring(0, index);
            } else {
                return ip;
            }
        }
        ip = request.getHeader("X-Real-IP");
        if (StringUtils.isNotEmpty(ip) && !"unKnown".equalsIgnoreCase(ip)) {
            return ip;
        }
        return request.getRemoteAddr();
    }
    
    }

小程序请求 wx.requestPayment

obj为后台返回的支付信息
requestPayment:function(obj){
    console.log("拉起微信支付页面并发送支付请求" + obj)
    wx.requestPayment(
      {
        'timeStamp': obj.data.timeStamp,
        'nonceStr':  obj.data.nonceStr,
        'package':   obj.data.package,
        'signType':  'MD5',
        'paySign':   obj.data.paySign,
        'success': function (res) { 
          console.log("支付成功返回参数"+res)
          console.log("支付成功")
        },
        'fail': function (res) {
          console.log("支付失败")
         }
      })
  }

效果图

哈哈哈看到这个图是不是感觉很可爱，如果后台返回数据没问题的话到这基本就成功了，拿开发者账号对应的微信来扫码就可以付款啦，快去调试一把吧……

支付成功后的回调问题下一篇再做介绍……嘿嘿