微信小程序支付：普通支付

package example.payment;

import java.util.LinkedHashMap;
import java.util.Map;
import com.wechat.pay.java.core.RSAPublicKeyConfig;
import com.wechat.pay.java.core.notification.NotificationParser;
import com.wechat.pay.java.core.notification.RequestParam;
import com.wechat.pay.java.service.payments.jsapi.JsapiServiceExtension;
import com.wechat.pay.java.service.payments.jsapi.model.Amount;
import com.wechat.pay.java.service.payments.jsapi.model.Payer;
import com.wechat.pay.java.service.payments.jsapi.model.PrepayRequest;
import com.wechat.pay.java.service.payments.jsapi.model.QueryOrderByOutTradeNoRequest;
import com.wechat.pay.java.service.payments.model.Transaction;

public final class WechatPayClient {
  private final String appId = required("WECHAT_PAY_APP_ID");
  private final String mchId = required("WECHAT_PAY_MCH_ID");
  private final String notifyUrl = required("WECHAT_PAY_NOTIFY_URL");
  private final JsapiServiceExtension service;
  private final NotificationParser parser;

  public WechatPayClient() {
    RSAPublicKeyConfig config = new RSAPublicKeyConfig.Builder()
        .merchantId(mchId)
        .privateKeyFromPath(required("WECHAT_PAY_PRIVATE_KEY_PATH"))
        .merchantSerialNumber(required("WECHAT_PAY_MERCHANT_SERIAL"))
        .publicKeyFromPath(required("WECHAT_PAY_PUBLIC_KEY_PATH"))
        .publicKeyId(required("WECHAT_PAY_PUBLIC_KEY_ID"))
        .apiV3Key(required("WECHAT_PAY_API_V3_KEY"))
        .build();
    service = new JsapiServiceExtension.Builder().config(config).build();
    parser = new NotificationParser(config);
  }

  public Map<String, String> prepay(String outTradeNo, String description,
      long totalFen, String openid) {
    if (totalFen <= 0 || totalFen > Integer.MAX_VALUE) {
      throw new IllegalArgumentException("订单金额超出支持范围");
    }
    if (openid == null || openid.isBlank()) {
      throw new IllegalArgumentException("缺少付款人的 OpenID");
    }
    Amount amount = new Amount();
    amount.setTotal(Math.toIntExact(totalFen));
    amount.setCurrency("CNY");
    Payer payer = new Payer();
    payer.setOpenid(openid);
    PrepayRequest request = new PrepayRequest();
    request.setAppid(appId);
    request.setMchid(mchId);
    request.setDescription(description);
    request.setOutTradeNo(outTradeNo);
    request.setNotifyUrl(notifyUrl);
    request.setAmount(amount);
    request.setPayer(payer);
    var result = service.prepayWithRequestPayment(request);
    Map<String, String> params = new LinkedHashMap<>();
    params.put("timeStamp", result.getTimeStamp());
    params.put("nonceStr", result.getNonceStr());
    params.put("package", result.getPackageVal());
    params.put("signType", result.getSignType());
    params.put("paySign", result.getPaySign());
    return params;
  }

  public Transaction query(String outTradeNo) {
    QueryOrderByOutTradeNoRequest request = new QueryOrderByOutTradeNoRequest();
    request.setMchid(mchId);
    request.setOutTradeNo(outTradeNo);
    return service.queryOrderByOutTradeNo(request);
  }

  public Transaction parseNotification(String serial, String nonce,
      String signature, String timestamp, String rawBody) {
    RequestParam request = new RequestParam.Builder()
        .serialNumber(serial).nonce(nonce).signature(signature)
        .timestamp(timestamp).body(rawBody).build();
    return parser.parse(request, Transaction.class);
  }

  // expected 参数必须来自本地保存的支付订单。
  public void checkPaid(Transaction tx, String outTradeNo,
      long expectedFen, String expectedOpenid) {
    boolean valid = tx != null
        && Transaction.TradeStateEnum.SUCCESS == tx.getTradeState()
        && appId.equals(tx.getAppid()) && mchId.equals(tx.getMchid())
        && outTradeNo.equals(tx.getOutTradeNo())
        && tx.getTransactionId() != null && !tx.getTransactionId().isBlank()
        && tx.getAmount() != null && tx.getAmount().getTotal() != null
        && tx.getAmount().getTotal().longValue() == expectedFen
        && "CNY".equals(tx.getAmount().getCurrency())
        && tx.getPayer() != null && expectedOpenid != null
        && expectedOpenid.equals(tx.getPayer().getOpenid());
    if (!valid) throw new IllegalStateException("支付结果与本地订单不一致");
  }

  private static String required(String name) {
    String value = System.getenv(name);
    if (value == null || value.isBlank()) {
      throw new IllegalStateException("缺少环境变量：" + name);
    }
    return value;
  }
}

package example.payment;

import java.util.Map;
import com.wechat.pay.java.service.payments.model.Transaction;
import nexus.io.tio.boot.http.TioRequestContext;
import nexus.io.tio.http.common.HttpRequest;
import nexus.io.tio.http.common.HttpResponse;

public final class WechatNotifyHandler {
  public interface PaidOrderService {
    // 正常返回表示核验通过且事务已提交；重复通知也必须核验。
    void confirm(Transaction transaction);
  }

  private final WechatPayClient client;
  private final PaidOrderService orders;

  public WechatNotifyHandler(WechatPayClient client, PaidOrderService orders) {
    this.client = client;
    this.orders = orders;
  }

  public HttpResponse notify(HttpRequest request) {
    try {
      Transaction transaction = client.parseNotification(
          request.getHeader("wechatpay-serial"),
          request.getHeader("wechatpay-nonce"),
          request.getHeader("wechatpay-signature"),
          request.getHeader("wechatpay-timestamp"),
          request.getBodyString());
      orders.confirm(transaction);
      return TioRequestContext.getResponse().setStatus(200)
          .setJson(Map.of("code", "SUCCESS", "message", "成功"));
    } catch (RuntimeException e) {
      // 生产环境记录脱敏异常和请求编号，不记录密钥或通知全文。
      return TioRequestContext.getResponse().setStatus(500)
          .setJson(Map.of("code", "FAIL", "message", "通知处理失败"));
    }
  }
}

WechatPayClient payClient = new WechatPayClient();
WechatNotifyHandler handler = new WechatNotifyHandler(payClient, paidOrderService);
router.add(HttpMethod.POST, "/api/payments/wechat/notify", handler::notify);