Example analysis of calling WeChat payment function in Java

<p class="button" id="pay" onclick="payBox()">支付</p>

function payBox(){
    //获得支付的钱数
    var money = $(".money input").val();
    //后台路径，加上参数
    location.href = "/XXX/XXX/XXXX/XXXX?money ="+money;
}

public String getOpenId(){
  String code = getPara("code");
  String openid = "";
    if (StringUtils.isEmpty(openid) && !StringUtils.isEmpty(code)) {
      SnsAccessToken token = SnsAccessTokenApi.getSnsAccessToken("你的APPID","你的appsecret密码",
          code);
      openid = token.getOpenid();
    }
    getSession().setAttribute("openandid",openid);
    return openid;
}
public void index() throws Exception{
    String openid = getOpenId();
    //得到金额
    String money= getPara("money");
    Map<String ,String > map=new HashMap<String,String>();
    //获取随机串
    String nonceStr=UUID.randomUUID().toString().substring(0, 32);
    //可以是支付物品的订单号。一个号码，看自己怎么给
    String out_trade_no="123456789";
    //支付金额。微信默认支付是(1=0.01)的比例，下面是将金额换算成微信可识别的
    BigDecimal re1=new BigDecimal(expressCharge);
    BigDecimal re2=new BigDecimal(Float.toString(100.00f));
    Float aa = re1.multiply(re2).floatValue();
    String total_fee = String.valueOf(aa);
    String[] smill = total_fee.split("\\.");
    total_fee = smill[0];
    //微信的appid
    String appid="XXXXXXXXXXXXXXXXX";
    String mch_id="XXXXXXXXX";//商户号
    String body="xxxxxxx";//商品信息，可以自己起最好写英文
    //密匙,商户平台的支付API密匙，注意是商户平台，不是微信平台
    String key = "XXXXXXXXXXXXXXXXXXXXXXXXXXXX";
    long timestamp = System.currentTimeMillis() / 1000;
    map.put("appid", appid );
    map.put("mch_id", mch_id);
    map.put("nonce_str",nonceStr);
    map.put("body", body);
    map.put("out_trade_no", out_trade_no);
    map.put("total_fee", total_fee);
    map.put("spbill_create_ip",getRequest().getRemoteAddr());
    //这里是支付成功后返回的地址，微信会以XML形式放回数据,就是本篇文章的下一类(例：wxxml())方法名。
    map.put("notify_url", "http://www.XXXX.com/XXXX/XXXX/xxxx/wxxml");
    map.put("trade_type", "JSAPI");
    map.put("openid", openid);//传入OpenId
    //这里传入Map集合和key商户支付密匙
    String paySign=getPayCustomSign(map,key);
    map.put("sign",paySign);
    //将map转为XML格式
    String xml= ArrayToXml(map);
    //统一下单，这里不用改
    String url = "https://api.mch.weixin.qq.com/pay/unifiedorder";
    String xmlStr = HttpKit.post(url, xml);
    //prepayid由微信返回的 。
    String prepayid = "";
    if (xmlStr.indexOf("SUCCESS") != -1) {
      Map<String, String> map2 = doXMLParse(xmlStr);
      prepayid = (String) map2.get("prepay_id");
    }
    String paySign2=getPayCustomSign(signMap,key);
    setAttr("model", model);
    setAttr("appId", appid);
    setAttr("paytimestamp", String.valueOf(timestamp));
    setAttr("paynonceStr", nonceStr);
    setAttr("paypackage", "prepay_id="+prepayid);
    setAttr("paysignType","MD5");
    setAttr("paySign", paySign2);
    //去到确认支付页面,返回页面方式不同,(例：pay.html页面)，下面
    render("/XXXX/pay.html");
}
/**
* 获取支付所需签名
* @param ticket
* @param timeStamp
* @param card_id
* @param code
* @return
* @throws Exception
*/
public static String getPayCustomSign(Map<String, String> bizObj,String key) throws Exception {
    String bizString = FormatBizQueryParaMap(bizObj, false);
    return sign(bizString, key);
}
/**
* 字典排序
* @param paraMap
* @param urlencode
* @return
* @throws Exception
*/
public static String FormatBizQueryParaMap(Map<String, String> paraMap,
  boolean urlencode) throws Exception {
    String buff = "";
    try {
      List<Map.Entry<String, String>> infoIds = new ArrayList<Map.Entry<String, String>>(paraMap.entrySet());
      Collections.sort(infoIds,
          new Comparator<Map.Entry<String, String>>() {
      public int compare(Map.Entry<String, String> o1,
         Map.Entry<String, String> o2) {
         return (o1.getKey()).toString().compareTo(
                  o2.getKey());
            }
          });
      for (int i = 0; i < infoIds.size(); i++) {
        Map.Entry<String, String> item = infoIds.get(i);
        //System.out.println(item.getKey());
        if (item.getKey() != "") {
          String key = item.getKey();
          String val = item.getValue();
          if (urlencode) {
            val = URLEncoder.encode(val, "utf-8");
          }
          buff += key + "=" + val + "&";
        }
      }
      if (buff.isEmpty() == false) {
        buff = buff.substring(0, buff.length() - 1);
      }
    } catch (Exception e) {
      throw new Exception(e.getMessage());
    }
    return buff;
}
//支付所需签名处调用此方法
public static String sign(String content, String key)
  throws Exception{
    String signStr = "";
    signStr = content + "&key=" + key;
    return MD5(signStr).toUpperCase();
}
//上一方法，MD5加密处理
public final static String MD5(String s) {
    char hexDigits[]={&#39;0&#39;,&#39;1&#39;,&#39;2&#39;,&#39;3&#39;,&#39;4&#39;,&#39;5&#39;,&#39;6&#39;,&#39;7&#39;,&#39;8&#39;,&#39;9&#39;,&#39;A&#39;,&#39;B&#39;,&#39;C&#39;,&#39;D&#39;,&#39;E&#39;,&#39;F&#39;};
    try {
      byte[] btInput = s.getBytes();
      MessageDigest mdInst = MessageDigest.getInstance("MD5");
      mdInst.update(btInput);
      byte[] md = mdInst.digest();
      int j = md.length;
      char str[] = new char[j * 2];
      int k = 0;
      for (int i = 0; i < j; i++) {
        byte byte0 = md[i];
        str[k++] = hexDigits[byte0 >>> 4 & 0xf];
        str[k++] = hexDigits[byte0 & 0xf];
      }
      return new String(str);
    } catch (Exception e) {
      e.printStackTrace();
      return null;
    }
}
//转为XML格式
public static String ArrayToXml(Map<String, String> arr) {
    String xml = "<xml>";
    Iterator<Entry<String, String>> iter = arr.entrySet().iterator();
    while (iter.hasNext()) {
      Entry<String, String> entry = iter.next();
      String key = entry.getKey();
      String val = entry.getValue();
      if (IsNumeric(val)) {
        xml += "<" + key + ">" + val + "</" + key + ">";
      } else
        xml += "<" + key + "><![CDATA[" + val + "]]></" + key + ">";
    }
    xml += "</xml>";
    return xml;
}
public static boolean IsNumeric(String str) {
    if (str.matches("\\d *")) {
      return true;
    } else {
      return false;
    }
}
//解析XML
private Map<String, String> doXMLParse(String xml)
    throws XmlPullParserException, IOException {
      InputStream inputStream = new ByteArrayInputStream(xml.getBytes());
      Map<String, String> map = null;
      XmlPullParser pullParser = XmlPullParserFactory.newInstance()
          .newPullParser();
      pullParser.setInput(inputStream, "UTF-8");// 为xml设置要解析的xml数据
      int eventType = pullParser.getEventType();
      while (eventType != XmlPullParser.END_DOCUMENT) {
        switch (eventType) {
        case XmlPullParser.START_DOCUMENT:
          map = new HashMap<String, String>();
          break;
        case XmlPullParser.START_TAG:
          String key = pullParser.getName();
          if (key.equals("xml"))
            break;
          String value = pullParser.nextText();
          map.put(key, value);
          break;
        case XmlPullParser.END_TAG:
          break;
        }
        eventType = pullParser.next();
      }
      return map;
}

<input type="hidden" name="appId" value="${appId}" id="appid" />

var appid = $("#appid").val();

<script type="text/javascript" src="${staticPath}/front/js/weixin.js"></script>

<p class="button" id="onlinePayNow">确认支付</p>

//先写一个点击事件，当点击id为onlinePayNow的按钮时，触发该事件。
$("#onlinePayNow").click(function getpay(){
  if (typeof WeixinJSBridge=="undefined") {
    if (document.addEventListener) {document.addEventListener('WeixinJSBridgeReady',onBridgeReady,false);
    }else if(document.attachEvent){document.attachEvent('WeixinJSBridgeReady',onBridgeReady);document.attachEvent('onWeixinJSBridgeReady',onBridgeReady);
    }
  }else{
    //如果报错，可用下面方法看看是不是参数缺少。
    /* alert('${appId}');
    alert('${paytimestamp}');
    alert('${paynonceStr}');
    alert('${paypackage}');
    alert('${paysignType}');
    alert('${paySign}'); */
    //调用下面方法。开启微信支付。
    onBridgeReady();
  }
})
function onBridgeReady(){
  WeixinJSBridge.invoke('getBrandWCPayRequest', {
    "appId" : '${appId}', //公众号名称，由商户传入
    "timeStamp" : '${paytimestamp}', //时间戳，自1970年以来的秒数
    "nonceStr" : '${paynonceStr}', //随机串
    "package" : '${paypackage}',
    "signType" : '${paysignType}', //微信签名方式:
    "paySign" : '${paySign}' //微信签名
  }, function(res) {
    //alert(res.err_msg); // 使用以上方式判断前端返回,微信团队郑重提示：res.err_msg将在用户支付成功后返
    if(res.err_msg == "get_brand_wcpay_request:ok"){
    //支付成功，完成后去到哪个页面。
    window.location.href="/XXXX/xxxx.html" rel="external nofollow" ;
    }
  });
}

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.math.BigDecimal;
import java.net.URLEncoder;
import java.security.MessageDigest;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.UUID;
import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import org.xmlpull.v1.XmlPullParserFactory;
import com.jfinal.kit.HttpKit;
import com.uitrs.express.common.Constants;