随着网络编程的飞速成长，网络平台的高频使用，当然就涉及到支付的功能。现在两支付渠道巨头（微信，支付宝），作为写程序的我们，当然会遇到公司需要对接此类业务的需求。

今天我们就来讲讲 ：app的微信支付Java实现

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首先我们需要拿到微信的商户号，appid，秘钥等信息。在微信支付自己账号下获取。
之后我们查看微信支付统一下单的api接口文档。
https://pay.weixin.qq.com/wiki/doc/api/app/app.php?chapter=9_1
具体中文注释查看此网站，我们看一下xml的demo

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流程比较啰嗦，上代码。
首先是一些工具类：
1: 自己微信支付基本信息类

public class ConfigUtil {
    /**
     * 服务号相关信息
     */
    public final static String APPID = "";//服务号的应用号
    public final static String MCH_ID = "";//商户号
    public final static String API_KEY = "";//API密钥
    public final static String SIGN_TYPE = "MD5";//签名加密方式


    public final static String UNIFIED_ORDER_URL = "https://api.mch.weixin.qq.com/pay/unifiedorder";//请求下单的http
}

2 :签名类 utf-8格式

 public static String createSign(String characterEncoding, SortedMap<Object, Object> parameters) {
        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();
            Object v = entry.getValue();
            if (null != v && !"".equals(v)
                    && !"sign".equals(k) && !"key".equals(k)) {
                sb.append(k + "=" + v + "&");
            }
        }
        sb.append("key=" + ConfigUtil.API_KEY);
        String sign = MD5Util.MD5Encode(sb.toString(), characterEncoding).toUpperCase();
        return sign;
    }

3：将map数组拼装成xml

 public static String getRequestXml(SortedMap<Object, Object> parameters) {
        StringBuffer sb = new StringBuffer();
        sb.append("<xml>");
        Set es = parameters.entrySet();
        Iterator it = es.iterator();
        while (it.hasNext()) {
            Map.Entry entry = (Map.Entry) it.next();
            String k = (String) entry.getKey();
            String v = (String) entry.getValue();
            if ("attach".equalsIgnoreCase(k) || "body".equalsIgnoreCase(k)) {
                sb.append("<" + k + ">" + "<![CDATA[" + v + "]]></" + k + ">");
            } else {
                sb.append("<" + k + ">" + v + "</" + k + ">");
            }
        }
        sb.append("</xml>");
        return sb.toString();
    }

4: SSL协议发起http请求

 /**
     * 发送https请求
     *
     * @param requestUrl    请求地址
     * @param requestMethod 请求方式（GET、POST）
     * @param outputStr     提交的数据
     * @return 返回微信服务器响应的信息
     */
    public static String httpsRequest(String requestUrl, String requestMethod, String outputStr) {
        try {
            // 创建SSLContext对象，并使用我们指定的信任管理器初始化
            TrustManager[] tm = {new MyX509TrustManager()};
            SSLContext sslContext = SSLContext.getInstance("SSL", "SunJSSE");
            sslContext.init(null, tm, new java.security.SecureRandom());
            // 从上述SSLContext对象中得到SSLSocketFactory对象
            SSLSocketFactory ssf = sslContext.getSocketFactory();
            URL url = new URL(requestUrl);
            HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
            //conn.setSSLSocketFactory(ssf);
            conn.setDoOutput(true);
            conn.setDoInput(true);
            conn.setUseCaches(false);
            // 设置请求方式（GET/POST）
            conn.setRequestMethod(requestMethod);
            conn.setRequestProperty("content-type", "application/x-www-form-urlencoded");
            // 当outputStr不为null时向输出流写数据
            if (null != outputStr) {
                OutputStream outputStream = conn.getOutputStream();
                // 注意编码格式
                outputStream.write(outputStr.getBytes("UTF-8"));
                outputStream.close();
            }
            // 从输入流读取返回内容
            InputStream inputStream = conn.getInputStream();
            InputStreamReader inputStreamReader = new InputStreamReader(inputStream, "UTF-8");
            BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
            String str = null;
            StringBuffer buffer = new StringBuffer();
            while ((str = bufferedReader.readLine()) != null) {
                buffer.append(str);
            }
            // 释放资源
            bufferedReader.close();
            inputStreamReader.close();
            inputStream.close();
            inputStream = null;
            conn.disconnect();
            return buffer.toString();
        } catch (ConnectException ce) {
//          log.error("连接超时：{}", ce);
        } catch (Exception e) {
//          log.error("https请求异常：{}", e);
        }
        return null;
    }

5：生成随机字符串

 public static String CreateNoncestr() {
        String chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        String res = "";
        for (int i = 0; i < 16; i++) {
            Random rd = new Random();
            res += chars.charAt(rd.nextInt(chars.length() - 1));
        }
        return res;
    }

6 将返回的xml 转换成map数组

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.jdom.Document;
import org.jdom.Element;
import org.jdom.JDOMException;
import org.jdom.input.SAXBuilder;


public class XMLUtil {
    /**
     * 解析xml,返回第一级元素键值对。如果第一级元素有子节点，则此节点的值是子节点的xml数据。
     *
     * @param strxml
     * @return
     * @throws JDOMException
     * @throws IOException
     */
    public static Map doXMLParse(String strxml) throws JDOMException, IOException {
        strxml = strxml.replaceFirst("encoding=\".*\"", "encoding=\"UTF-8\"");

        if (null == strxml || "".equals(strxml)) {
            return null;
        }
        Map m = new HashMap();

        InputStream in = new ByteArrayInputStream(strxml.getBytes("UTF-8"));
        SAXBuilder builder = new SAXBuilder();
        Document doc = builder.build(in);
        Element root = doc.getRootElement();
        List list = root.getChildren();
        Iterator it = list.iterator();
        while (it.hasNext()) {
            Element e = (Element) it.next();
            String k = e.getName();
            String v = "";
            List children = e.getChildren();
            if (children.isEmpty()) {
                v = e.getTextNormalize();
            } else {
                v = XMLUtil.getChildrenText(children);
            }

            m.put(k, v);
        }

        //关闭流
        in.close();

        return m;
    }

    /**
     * 获取子结点的xml
     *
     * @param children
     * @return String
     */
    public static String getChildrenText(List children) {
        StringBuffer sb = new StringBuffer();
        if (!children.isEmpty()) {
            Iterator it = children.iterator();
            while (it.hasNext()) {
                Element e = (Element) it.next();
                String name = e.getName();
                String value = e.getTextNormalize();
                List list = e.getChildren();
                sb.append("<" + name + ">");
                if (!list.isEmpty()) {
                    sb.append(XMLUtil.getChildrenText(list));
                }
                sb.append(value);
                sb.append("</" + name + ">");
            }
        }

        return sb.toString();
    }

}

7.MD5的工具类

import java.security.MessageDigest;

public class MD5Util {

    private static String byteArrayToHexString(byte b[]) {
        StringBuffer resultSb = new StringBuffer();
        for (int i = 0; i < b.length; i++)
            resultSb.append(byteToHexString(b[i]));

        return resultSb.toString();
    }

    private static String byteToHexString(byte b) {
        int n = b;
        if (n < 0)
            n += 256;
        int d1 = n / 16;
        int d2 = n % 16;
        return hexDigits[d1] + hexDigits[d2];
    }

    public static String MD5Encode(String origin, String charsetname) {
        String resultString = null;
        try {
            resultString = new String(origin);
            MessageDigest md = MessageDigest.getInstance("MD5");
            if (charsetname == null || "".equals(charsetname))
                resultString = byteArrayToHexString(md.digest(resultString
                        .getBytes()));
            else
                resultString = byteArrayToHexString(md.digest(resultString
                        .getBytes(charsetname)));
        } catch (Exception exception) {
        }
        return resultString;
    }

    private static final String hexDigits[] = {"0", "1", "2", "3", "4", "5",
            "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};

}

8.是否签名正确,规则是:按参数名称a-z排序,遇到空值的参数不参加签名

    /**
     * 是否签名正确,规则是:按参数名称a-z排序,遇到空值的参数不参加签名。
     *
     * @return boolean
     */
    public static boolean isTenpaySign(String characterEncoding, SortedMap<Object, Object> packageParams) {
        StringBuffer sb = new StringBuffer();
        Set es = packageParams.entrySet();
        Iterator it = es.iterator();
        while (it.hasNext()) {
            Map.Entry entry = (Map.Entry) it.next();
            String k = (String) entry.getKey();
            String v = (String) entry.getValue();
            if (!"sign".equals(k) && null != v && !"".equals(v)) {
                sb.append(k + "=" + v + "&");
            }
        }

        sb.append("key=" + ConfigUtil.API_KEY);

        //算出摘要
        String mysign = MD5Util.MD5Encode(sb.toString(), characterEncoding).toLowerCase();
        String tenpaySign = ((String) packageParams.get("sign")).toLowerCase();

        //System.out.println(tenpaySign + "    " + mysign);
        return tenpaySign.equals(mysign);
    }

9 信任管理器

import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import javax.net.ssl.X509TrustManager;

/**
 * 信任管理器
 */
public class MyX509TrustManager implements X509TrustManager {

    // 检查客户端证书
    public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {
    }

    // 检查服务器端证书
    public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {
    }

    // 返回受信任的X509证书数组
    public X509Certificate[] getAcceptedIssuers() {
        return null;
    }
}

基本工具类都在这里，接下来就是下单的controller类,
因为含有业务逻辑的代码就不上了，直接贴下单的那部分

//测试环境
//微信默认从单位为分，所以用此方法将单位调整成元
  int price100 = new BigDecimal(price).multiply(new BigDecimal(100)).intValue();
            SortedMap<Object, Object> parameters = new TreeMap<Object, Object>();
            parameters.put("appid", ConfigUtil.APPID);
            parameters.put("mch_id", ConfigUtil.MCH_ID);
            parameters.put("nonce_str", noPayOrder.getWxOutTradeNo());
            parameters.put("body", message);
            parameters.put("out_trade_no", UUID.randomUUID().toString().substring(0, 15)); //订单id
            parameters.put("fee_type", "CNY");
            parameters.put("total_fee", String.valueOf(price100));
            parameters.put("spbill_create_ip", "127.0.0.1");
            parameters.put("notify_url", returnUrl);
            parameters.put("trade_type", "APP");
            //设置签名
            String sign = PayCommonUtil.createSign("UTF-8", parameters);
            parameters.put("sign", sign);
            //封装请求参数结束
            String requestXML = PayCommonUtil.getRequestXml(parameters);
            //调用统一下单接口
            String result = PayCommonUtil.httpsRequest(ConfigUtil.UNIFIED_ORDER_URL, "POST", requestXML);
            System.out.println("\n" + result);
            try {
                /**统一下单接口返回正常的prepay_id，再按签名规范重新生成签名后，将数据传输给APP。参与签名的字段名为appId，partnerId，prepayId，nonceStr，timeStamp，package。注意：package的值格式为Sign=WXPay**/
                Map<String, String> map = XMLUtil.doXMLParse(result);
                SortedMap<Object, Object> parameterMap2 = new TreeMap<Object, Object>();
                parameterMap2.put("appid", ConfigUtil.APPID);
                parameterMap2.put("partnerid", ConfigUtil.MCH_ID);
                parameterMap2.put("prepayid", map.get("prepay_id"));
                parameterMap2.put("package", "Sign=WXPay");
                parameterMap2.put("noncestr", PayCommonUtil.CreateNoncestr());
                //本来生成的时间戳是13位，但是ios必须是10位，所以截取了一下
                parameterMap2.put("timestamp", Long.parseLong(String.valueOf(System.currentTimeMillis()).toString().substring(0, 10)));
                String sign2 = PayCommonUtil.createSign("UTF-8", parameterMap2);
                parameterMap2.put("sign", sign2);//此 parameterMap2内容送到ios调用就可以了
               /* landlordNew.setWxSign(sign2);
                this.landlordNewService.update(landlordNew);*/
                resultMap.put("code", "200");
                resultMap.put("msg", parameterMap2);
            } catch (JDOMException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

将最后生成的parameterMap2内容送到ios调用就完成支付调用。

好了支付调用成功了，用户付完款肯定是需要回调来完成支付成功后的业务逻辑了（用户成功支付后，微信会主动调用我们预先设置好的url（需要外网链接），同时微信会将：商户订单号,微信支付订单号发送给我们，我们可以通过这些来完成业务逻辑）下面为回调接口代码：

/**
     * 微信异步通知 （签约支付）
     */
    @RequestMapping("/wxNotifySignContract")
    public void wxNotifySignContract(HttpServletRequest request, HttpServletResponse response) throws IOException, JDOMException {

        try {
            //读取参数
            InputStream inputStream;
            StringBuffer sb = new StringBuffer();
            inputStream = request.getInputStream();
            String s;
            BufferedReader in = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"));
            while ((s = in.readLine()) != null) {
                sb.append(s);
            }
            in.close();
            inputStream.close();
            //解析xml成map
            Map<String, String> m = new HashMap<String, String>();
            m = XMLUtil.doXMLParse(sb.toString());
            for (Object keyValue : m.keySet()) {
                System.out.println(keyValue + "=" + m.get(keyValue));
            }
            //过滤空 设置 TreeMap
            SortedMap<Object, Object> packageParams = new TreeMap<Object, Object>();
            Iterator it = m.keySet().iterator();
            while (it.hasNext()) {
                String parameter = (String) it.next();
                String parameterValue = m.get(parameter);

                String v = "";
                if (null != parameterValue) {
                    v = parameterValue.trim();
                }
                packageParams.put(parameter, v);
            }

            //判断签名是否正确
            String resXml = "";
            if (PayCommonUtil.isTenpaySign("UTF-8", packageParams)) {
                if ("SUCCESS".equals((String) packageParams.get("result_code"))) {
                    // 这里是支付成功
                    //////////执行自己的业务逻辑////////////////
                    String appid = (String) packageParams.get("appid");//appid
                    String sign = (String) packageParams.get("sign");//签名
                    String total_fee = (String) packageParams.get("total_fee");//总金额
                    String mch_id = (String) packageParams.get("mch_id"); //商户号
                    String openid = (String) packageParams.get("openid");  //用户标识

                //微信回调 商户号回调的商户订单号是out_trade_no
               //（需要唯一，同一个订单号执行下单接口会报错），这里笔者使用
              //nonce_str作为订单号，后续还需要改动。这个字段官方文档解释为随机字
              //符串，但后来发现回调的时候返回的nonce_str跟下单填进去的nonce_str
             //一致，所以暂时用来当订单号了。）
                    String out_trade_no = (String) packageParams.get("nonce_str"); //商户订单号
                    String transaction_id = (String) packageParams.get("transaction_id"); //微信支付订单号
                    this.contractpayReturn(appid, sign, total_fee, mch_id, openid, out_trade_no, transaction_id);
                    resXml = "<xml>" + "<return_code><![CDATA[SUCCESS]]></return_code>"
                            + "<return_msg><![CDATA[OK]]></return_msg>" + "</xml> ";
                } else {
                    logger.info("支付失败,错误信息：" + packageParams.get("err_code"));
                    resXml = "<xml>" + "<return_code><![CDATA[FAIL]]></return_code>"
                            + "<return_msg><![CDATA[报文为空]]></return_msg>" + "</xml> ";
                }
            } else {
                resXml = "<xml>" + "<return_code><![CDATA[FAIL]]></return_code>"
                        + "<return_msg><![CDATA[通知签名验证失败]]></return_msg>" + "</xml> ";
                logger.info("通知签名验证失败");
            }
            //------------------------------
            //处理业务完毕
            //------------------------------
            BufferedOutputStream out = new BufferedOutputStream(
                    response.getOutputStream());
            out.write(resXml.getBytes());
            out.flush();
            out.close();
            logger.error("微信回调接口成功--------");
        } catch (Exception ex) {
            logger.error(ex.toString());
            ExceptionUntil.setLogger(logger, ex);
            logger.error("微信回调接口失败--------");
        }

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实现结果展示

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