微信最新版小程序支付支付回调的java代码

以下是微信最新版小程序支付的支付回调Java代码示例：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class WxPayNotifyServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    private static final String SUCCESS = "SUCCESS";
    private static final String FAIL = "FAIL";
    private static final String SIGN_TYPE_MD5 = "MD5";
    private static final String SIGN_TYPE_HMAC_SHA256 = "HMAC-SHA256";

    private static final String APP_ID = "your_app_id";
    private static final String MCH_ID = "your_mch_id";
    private static final String API_KEY = "your_api_key";

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(request.getInputStream()));
        StringBuffer buffer = new StringBuffer();
        String line = "";
        while ((line = reader.readLine()) != null) {
            buffer.append(line);
        }
        reader.close();

        String notifyXml = buffer.toString();
        Map<String, String> notifyMap = parseXmlToMap(notifyXml);

        String returnCode = notifyMap.get("return_code");
        if (SUCCESS.equals(returnCode)) {
            String appId = notifyMap.get("appid");
            String mchId = notifyMap.get("mch_id");
            String nonceStr = notifyMap.get("nonce_str");
            String sign = notifyMap.get("sign");
            String signType = notifyMap.get("sign_type");
            String resultCode = notifyMap.get("result_code");
            String transactionId = notifyMap.get("transaction_id");
            String outTradeNo = notifyMap.get("out_trade_no");
            String totalFee = notifyMap.get("total_fee");
            String attach = notifyMap.get("attach");

            if (APP_ID.equals(appId) && MCH_ID.equals(mchId)) {
                if (validateSign(notifyMap, API_KEY, signType, sign)) {
                    // 处理支付成功逻辑
                    // 更新订单状态等操作
                    response.getWriter().write(SUCCESS);
                    return;
                }
            }
        }

        response.getWriter().write(FAIL);
    }

    private Map<String, String> parseXmlToMap(String xml) {
        Map<String, String> map = new HashMap<String, String>();
        String[] strings = xml.split("<|>");
        for (int i = 2; i < strings.length; i += 4) {
            map.put(strings[i], strings[i + 2]);
        }
        return map;
    }

    private boolean validateSign(Map<String, String> map, String apiKey, String signType, String sign) {
        String signStr = generateSign(map, apiKey, signType);
        return signStr.equals(sign);
    }

    private String generateSign(Map<String, String> map, String apiKey, String signType) {
        StringBuffer buffer = new StringBuffer();
        for (String key : map.keySet()) {
            if (!"sign".equals(key) && !"key".equals(key) && map.get(key) != null && !"".equals(map.get(key))) {
                buffer.append(key).append("=").append(map.get(key)).append("&");
            }
        }
        buffer.append("key=").append(apiKey);

        String signStr = "";
        if (SIGN_TYPE_MD5.equals(signType)) {
            signStr = md5(buffer.toString()).toUpperCase();
        } else if (SIGN_TYPE_HMAC_SHA256.equals(signType)) {
            signStr = hmacSha256(buffer.toString(), apiKey).toUpperCase();
        }

        return signStr;
    }

    private String md5(String str) {
        MessageDigest md5 = null;
        try {
            md5 = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
            return "";
        }
        byte[] bytes = md5.digest(str.getBytes());
        StringBuffer stringBuffer = new StringBuffer();
        for (byte b : bytes) {
            int bt = b & 0xff;
            if (bt < 16) {
                stringBuffer.append(0);
            }
            stringBuffer.append(Integer.toHexString(bt));
        }
        return stringBuffer.toString();
    }

    private String hmacSha256(String str, String key) {
        try {
            Mac sha256Hmac = Mac.getInstance("HmacSHA256");
            SecretKeySpec secretKey = new SecretKeySpec(key.getBytes("UTF-8"), "HmacSHA256");
            sha256Hmac.init(secretKey);
            byte[] bytes = sha256Hmac.doFinal(str.getBytes("UTF-8"));
            StringBuffer stringBuffer = new StringBuffer();
            for (byte b : bytes) {
                String hex = Integer.toHexString(0xff & b);
                if (hex.length() == 1) {
                    stringBuffer.append('0');
                }
                stringBuffer.append(hex);
            }
            return stringBuffer.toString();
        } catch (Exception e) {
            e.printStackTrace();
            return "";
        }
    }
}

请注意，上面的代码示例仅供参考，具体实现需要根据自己的业务需求进行调整。