最近在整合微信支付，不得不說微信文件就是坑，說的不明不白，還是支付寶簡單，

流程：

1、客戶端提交訂單——》到（自己平臺的）伺服器，引數與服務端協商

2、服務端拿到請求訂單資訊——》參考微信統一下單介面——》把必須傳的引數進行加密轉XML傳到微信伺服器

3、如果簽名正確，微信服務端會返回成功資訊 ——》XML格式——》解析XML——》

拿到預支付交易會話標識（prepay_id）這個是關鍵

4、拿到交易會話ID後，進行二次簽名 把下表資料按照第一次簽名規範進行簽名——》傳到客戶端

5、（注意）二次簽名的隨機字串（noncestr）不要再次生成新的字串，一定要是第一次簽名傳

微信伺服器那個保持一至。（這點微信文件沒有找到）

6、二次簽名的資料就可以傳到客戶端——》客戶端呼叫拿到資料就可以呼叫微信支付了

7、一定要是正式打包的apk才會有效果，否則不能調起微信支付，

8、微信開發平臺設定好包名，以及應用簽名就可以了

直接上程式碼

再說下服務端 簡單寫的測試下，直接複製就能用，

/**
 * Servlet implementation class PayHttpServlet
 */
@WebServlet("/PayHttpServlet")
public class PayHttpServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	private String urlWx = "https://api.mch.weixin.qq.com/pay/unifiedorder";

	private String postType = "POST";

	private String result;

	private int price100 = -1;

	/**
	 * @see HttpServlet#HttpServlet()
	 */
	public PayHttpServlet() {
		super();
		// TODO Auto-generated constructor stub
	}

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		// response.getWriter().append("Served at: ").append(request.getContextPath());
		doPost(request, response);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		// 設定編碼
		response.setContentType("text/html;charset=utf-8");
		request.setCharacterEncoding("utf-8");
		String price = request.getParameter("price");

		if (price == null || "".equals(price)) {
			// 返回客戶端資料
			System.out.print("引數有誤，金額不能為0");
			return;
		} else {
			price100 = new BigDecimal(price).multiply(new BigDecimal(100)).intValue();
			doconfig(request, response);
		}

	}

	private void doconfig(HttpServletRequest request, HttpServletResponse response) {
		// TODO Auto-generated method stub
		Map<String, Object> resultMap = new HashMap<String, Object>();
		SortedMap<String, Object> map = new TreeMap<>();
		map.put("appid", PayCommonUtil.APPID);
		map.put("mch_id", PayCommonUtil.MCH_ID);
		map.put("nonce_str", PayCommonUtil.getRandomString(30));
		// map.put("sign", value);
		map.put("trade_type", "APP");
		map.put("body", "APP測試支付");
		map.put("out_trade_no", PayCommonUtil.getRandomString(15));
		map.put("total_fee", String.valueOf(price100));
		map.put("spbill_create_ip", "113.113.157.124");//ip地址
		map.put("notify_url", "http://www.baidu.com");//非同步通知地址
		// 簽名
		String singA = PayCommonUtil.createSign("utf-8", map);
		map.put("sign", singA);
		// 請求封裝
		String urlData = PayCommonUtil.getRequestXml(map);
		System.out.println("xml=" + "\n" + urlData);
		// 呼叫下單介面，得到prepay_id預支付碼，重新簽名返回給app
		String result = PayCommonUtil.httpsRequest(urlWx, postType, urlData);
		// System.out.println("xml="+urlData);
		System.out.println("resultXML=" + "\n" + result);
		// 得到資料返回給app
		try {
			Map<String, Object> map2 = PayCommonUtil.doXMLParse(result);

			SortedMap<String, Object> mapApp = new TreeMap<>();
			mapApp.put("appid", PayCommonUtil.APPID);
			mapApp.put("partnerid", PayCommonUtil.MCH_ID);
			mapApp.put("prepayid", map2.get("prepay_id"));
			mapApp.put("package", "Sign=WXPay");
			mapApp.put("noncestr", map.get("nonce_str"));
			System.out.println("nonce_str=="+map.get("nonce_str"));
			// 時間戳
			mapApp.put("timestamp",
					String.valueOf(Long.parseLong(String.valueOf(System.currentTimeMillis()).substring(0, 10))));
			String signAPP = PayCommonUtil.createSign("utf-8", mapApp);
			mapApp.put("sign", signAPP);
			mapApp.put("status", "1");

			try {
				String object = new Gson().toJson(mapApp);
				JSONObject object2 = new JSONObject(object);
				System.out.println("json=" + "\n" + object2);
				// 返回客戶端資料
				PrintWriter out = response.getWriter();
				out.write(object2.toString());

				out.flush();
				out.close();
			} catch (JSONException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}

			System.out.println("mapApp" + "\n" + mapApp);

		} catch (JDOMException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

	}

}
 

public class PayCommonUtil {
	// 微信引數配置
	public static String API_KEY = "";
	public static String APPID = "";
	public static String MCH_ID = "";

	// 隨機字串生成
	public static String getRandomString(int length) { // length表示生成字串的長度
		String base = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
		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();
	}

	// 請求xml組裝
	public static String getRequestXml(SortedMap<String, 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 key = (String) entry.getKey();
			String value = (String) entry.getValue();
			if ("attach".equalsIgnoreCase(key) || "body".equalsIgnoreCase(key) || "sign".equalsIgnoreCase(key)) {
				sb.append("<" + key + ">" + "<![CDATA[" + value + "]]></" + key + ">");
			} else {
				sb.append("<" + key + ">" + value + "</" + key + ">");
			}
		}
		sb.append("</xml>");
		return sb.toString();
	}

	/**
	 * 所有引數除sign外，按照ASCII碼排序，
	 */
	public static String buildASCiiParams(Map<String, Object> params) {
		StringBuffer stringBuffer = new StringBuffer();// 存放資料
		// 按照ASCII碼進行排序
		Map<String, Object> sortMap = new TreeMap<String, Object>(params);
		// 便利字典，拼接"key=value&key=value"
		for (Map.Entry<String, Object> m : sortMap.entrySet()) {
			if (stringBuffer.length() > 0) {
				stringBuffer.append("&");
			}
			stringBuffer.append(m.getKey()).append("=").append(m.getValue());
		}
		return stringBuffer.toString();
	}

	// 生成簽名
	public static String createSign(String characterEncoding, SortedMap<String, 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=" + API_KEY);
		String sign = MD5Utils.MD5Encode(sb.toString(), characterEncoding).toUpperCase();
		return sign;
	}

	// 請求方法
	public static String httpsRequest(String requestUrl, String requestMethod, String outputStr) {
		try {

			URL url = new URL(requestUrl);
			HttpURLConnection conn = (HttpURLConnection) url.openConnection();

			conn.setDoOutput(true);
			conn.setDoInput(true);
			conn.setUseCaches(false);
			// 設定請求方式（GET/POST）
			conn.setRequestMethod(requestMethod);
			conn.setRequestProperty("content-type", "application/x-www-form-urlencoded");
			// 當outputStr不為null時向輸出流寫資料
			if (null != outputStr) {
				OutputStream outputStream = (OutputStream) conn.getOutputStream();
				// 注意編碼格式
				outputStream.write(outputStr.getBytes("UTF-8"));
				outputStream.close();
			}
			// 從輸入流讀取返回內容
			InputStream 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);
			}
			// 釋放資源
			bufferedReader.close();
			inputStreamReader.close();
			inputStream.close();
			inputStream = null;
			conn.disconnect();
			return buffer.toString();
		} catch (ConnectException ce) {
			System.out.println("連線超時：{}" + ce);
		} catch (Exception e) {
			System.out.println("https請求異常：{}" + e);
		}
		return null;
	}

	// xml解析
	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 = getChildrenText(children);
			}

			m.put(k, v);
		}

		// 關閉流
		in.close();

		return m;
	}

	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(getChildrenText(list));
				}
				sb.append(value);
				sb.append("</" + name + ">");
			}
		}

		return sb.toString();
	}

}