本文直接从代码调用微信扫码支付讲起。账号配置，参数生成等请参考官方文档：https://pay.weixin.qq.com/wiki/doc/api/native.php?chapter=6_1
微信扫码支付。简单来说，就是你把微信支付需要的信息，生成到二维码图片中。通过微信扫一扫，发起支付。我们需要做的就是二件事：
一是：按照微信扫码支付规则生成二维码信息.
二是：微信没有提供生成二维码图片的接口。需要我们自己把二维码信息生成到二维码图片中。
1.模式选择：
微信扫码支付，有两种模式，文档中有介绍。第二种模式，微信接口会返回二维码信息给我们。而第一种模式则需要我们自己去生成二维码信息。会有些麻烦。尤其 是参数大小写，还有签名的问题，容易出错。总的来说第二种模式比第一种模式简单。所有我采用的是第二种模式，比较通用。京东与携程亦用的是第二种模式。
2.调用统一下单接口获取带有二维码信息的url：（模式二）
模式二的微信扫码支付，需要先调用微信的统一下单接口，生成预交易单。（参数传递与接收都是XML 数据格式。）
正确调用后，会返回含有交易标示ID，和二维码链接的URL。
3.实现扫码支付（模式二）
private static String APPID = ""; private static String MCHID= "";
private static String KEY= "";
private static String APPSECRET= "";
private static String body= "";
private static String notify_url= ""; //回调地址。测试回调必须保证外网能访问到此地址
/**
* 统一下单接口
* 微信二维码支付
* @param params
* @return
*/
public String weixin_pay(String out_trade_no,String product_id) {
JSONObject retJson = new JSONObject();
try { String currTime = PayCommonUtil.getCurrTime();
String strTime = currTime.substring(8, currTime.length());
String strRandom = PayCommonUtil.buildRandom(4) + "";
String nonce_str = strTime + strRandom; //生成随机字符串 JSONObject requestObj = JSONObject.fromObject(params); // 正式上线的时候价格根据订单id查询
String order_price = "1"; // 价格 注意：价格的单位是分 SortedMap<Object, Object> packageParams = new TreeMap<Object, Object>();
packageParams.put("appid", APPID);
packageParams.put("mch_id", MCHID);
packageParams.put("nonce_str", nonce_str);
packageParams.put("body", body);
packageParams.put("out_trade_no", out_trade_no);
packageParams.put("total_fee", order_price);
packageParams.put("spbill_create_ip", "用户端ip");
packageParams.put("notify_url", notify_url);
packageParams.put("trade_type", "NATIVE");
packageParams.put("product_id", product_id);
Calendar nowTime = Calendar.getInstance();
packageParams.put("time_start", DateFormatUtil.formatDate(
nowTime.getTime(), "yyyyMMddHHmmss"));
nowTime.add(Calendar.MINUTE, requestObj.getInt("expire_time"));
packageParams.put("time_expire", DateFormatUtil.formatDate(
nowTime.getTime(), "yyyyMMddHHmmss")); String sign = PayCommonUtil.createSign("UTF-8", packageParams,
KEY);
packageParams.put("sign", sign); //加密 String requestXML = PayCommonUtil.getRequestXml(packageParams);
logger.info("支付请求：" + requestXML);
long startTime=System.currentTimeMillis();
String resXml = HttpRequest.postData(
"https://api.mch.weixin.qq.com/pay/unifiedorder",
requestXML);
long endTime=System.currentTimeMillis(); Integer execute_time = (int) ((endTime-startTime)/1000);
logger.info("支付结果：" + resXml);
Map map = XMLUtil.doXMLParse(resXml); JSONObject reportParams = new JSONObject();
reportParams.put("url", "https://api.mch.weixin.qq.com/pay/unifiedorder");
reportParams.put("execute_time", execute_time);
reportParams.put("return_code", map.get("return_code").toString());
reportParams.put("return_msg", map.get("return_msg").toString());
reportParams.put("result_code", map.get("result_code").toString());
if (map.get("err_code") != null) {
reportParams.put("err_code", map.get("err_code").toString());
reportParams.put("err_code_des", map.get("err_code_des").toString());
}
reportParams.put("out_trade_no", out_trade_no);
//交易保障
report(reportParams.toString());
if (map.get("return_code").toString().equals("SUCCESS") && map.get("result_code").toString().equals("SUCCESS")) {
String urlCode = (String) map.get("code_url"); //微信二维码短链接
retJson.put("code", 0);
retJson.put("message", "下单成功.");
retJson.put("data", urlCode);
} else {
retJson.put("code", 1);
retJson.put("message", map.get("err_code_des").toString());
retJson.put("data", "");
}
return retJson.toString();
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
}
4.支付工具类
public class PayCommonUtil {
public static Logger log = LoggerFactory.getLogger(PayCommonUtil.class);
/**
* 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, String API_KEY) {
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=" + API_KEY);
//算出摘要
String mysign = MD5.MD5Encode(sb.toString(), characterEncoding).toLowerCase();
String tenpaySign = ((String)packageParams.get("sign")).toLowerCase();
//System.out.println(tenpaySign + " " + mysign);
return tenpaySign.equals(mysign);
}
/**
* @author
* @date 2016-4-22
* @Description：sign签名
* @param characterEncoding
* 编码格式
* @param parameters
* 请求参数
* @return
*/
public static String createSign(String characterEncoding, SortedMap<Object, Object> packageParams, String API_KEY) {
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 = "";
try {
v = (String) entry.getValue();
} catch (Exception e) {
// TODO: handle exception
v = entry.getValue() + "";
}
if (null != v && !"".equals(v) && !"sign".equals(k) && !"key".equals(k)) {
sb.append(k + "=" + v + "&");
}
}
sb.append("key=" + API_KEY);
String sign = MD5.MD5Encode(sb.toString(), characterEncoding).toUpperCase();
return sign;
}
/**
* @author
* @date 2016-4-22
* @Description：将请求参数转换为xml格式的string
* @param parameters
* 请求参数
* @return
*/
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 = "";
try {
v = (String) entry.getValue();
} catch (Exception e) {
// TODO: handle exception
v = entry.getValue() + "";
}
if ("attach".equalsIgnoreCase(k) || "body".equalsIgnoreCase(k) || "sign".equalsIgnoreCase(k)) {
sb.append("<" + k + ">" + "<![CDATA[" + v + "]]></" + k + ">");
} else {
sb.append("<" + k + ">" + v + "</" + k + ">");
}
}
sb.append("</xml>");
return sb.toString();
}
/**
* 取出一个指定长度大小的随机正整数.
*
* @param length
* int 设定所取出随机数的长度。length小于11
* @return int 返回生成的随机数。
*/
public static int buildRandom(int length) {
int num = 1;
double random = Math.random();
if (random < 0.1) {
random = random + 0.1;
}
for (int i = 0; i < length; i++) {
num = num * 10;
}
return (int) ((random * num));
}
/**
* 获取当前时间 yyyyMMddHHmmss
*
* @return String
*/
public static String getCurrTime() {
Date now = new Date();
SimpleDateFormat outFormat = new SimpleDateFormat("yyyyMMddHHmmss");
String s = outFormat.format(now);
return s;
}
public static JSONObject httpsRequestToJsonObject(String requestUrl,
String requestMethod, String outputStr) {
JSONObject jsonObject = null;
try {
StringBuffer buffer = httpsRequest(requestUrl, requestMethod,
outputStr);
jsonObject = JSONObject.fromObject(buffer.toString());
} catch (ConnectException ce) {
log.error("连接超时：" + ce.getMessage());
} catch (Exception e) {
log.error("https请求异常：" + e.getMessage());
}
return jsonObject;
}
private static StringBuffer httpsRequest(String requestUrl,
String requestMethod, String output)
throws NoSuchAlgorithmException, NoSuchProviderException,
KeyManagementException, MalformedURLException, IOException,
ProtocolException, UnsupportedEncodingException {
URL url = new URL(requestUrl);
HttpsURLConnection connection = (HttpsURLConnection) url
.openConnection();
connection.setDoOutput(true);
connection.setDoInput(true);
connection.setUseCaches(false);
connection.setRequestMethod(requestMethod);
if (null != output) {
OutputStream outputStream = connection.getOutputStream();
outputStream.write(output.getBytes("UTF-8"));
outputStream.close();
}
// 从输入流读取返回内容
InputStream inputStream = connection.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);
}
bufferedReader.close();
inputStreamReader.close();
inputStream.close();
inputStream = null;
connection.disconnect();
return buffer;
}
}