Java 接入微信支付详细全流程

获取对应参数开发

对应指引：开发必要参数说明

核心代码开发

推荐使用官方 SDK

https://github.com/wechatpay-apiv3/wechatpay-java

引入依赖

<dependency>
    <groupId>com.github.wechatpay-apiv3</groupId>
    <artifactId>wechatpay-java</artifactId>
    <version>0.4.13</version>
</dependency>

代码实现

配置类：

@Configuration
public class WeChatPayConfig {
    @Value("${wechat.pay.mchid}")
    private String mchId;

    @Value("${wechat.pay.mchSerialNo}")
    private String mchSerialNo;

    @Value("${wechat.pay.privateKeyPath}")
    private String privateKeyPath;

    @Value("${wechat.pay.apiV3Key}")
    private String apiV3Key;

    @Value("${wechat.pay.certPath}")
    private String certPath;

    /**
     * 创建私钥签名对象
     */
    @Bean
    public PrivateKey getPrivateKey() throws Exception {
        return PemUtil.loadPrivateKey(new FileInputStream(privateKeyPath));
    }

    /**
     * 创建自动更新的 Verifier (验证微信响应签名)
     */
    @Bean
    public Verifier getVerifier() throws Exception {
        ScheduledUpdateCertificatesVerifier verifier = new ScheduledUpdateCertificatesVerifier(
            new WechatPay2Credentials(mchId, new PrivateKeySigner(mchSerialNo, getPrivateKey())),
            apiV3Key.getBytes(StandardCharsets.UTF_8));
        return verifier;
    }

    /**
     * 创建 HttpClient (用于调用微信 API)
     */
    @Bean
    public CloseableHttpClient getWxPayClient() throws Exception {
        return WechatPayHttpClientBuilder.create()
            .withMerchant(mchId, mchSerialNo, getPrivateKey())
            .withValidator(new WechatPay2Validator(getVerifier()))
            .build();
    }
}

服务层（统一下单）示例：

@Override
public String createNativeOrder(String outTradeNo, int totalFee, String body) {
    // ... 构建请求参数 (类似 JSAPI，但去掉 payer，增加 scene_info 等)
    json.put("appid", appid);
    json.put("mchid", mchId);
    json.put("description", body);
    json.put("out_trade_no", outTradeNo);
    json.put("notify_url", "https://yourdomain.com/api/wxpay/notify");

    JSONObject amount = new JSONObject();
    amount.put("total", totalFee);
    amount.put("currency", "CNY");
    json.put("amount", amount);

    JSONObject sceneInfo = new JSONObject();
    sceneInfo.put("payer_client_ip", "用户 IP");
    json.put("scene_info", sceneInfo);

    try {
        HttpPost httpPost = new HttpPost("https://api.mch.weixin.qq.com/v3/pay/transactions/native");
        // ... 同上设置请求头和实体
        JSONObject result = JSON.parseObject(responseString);
        return result.getString("code_url");
    } catch (Exception e) {
        throw new RuntimeException("创建 Native 订单失败", e);
    }
}

回调处理

注意：此路径必须是公网能访问的路径

@RestController
@RequestMapping("/api/wxpay")
public class WeChatPayController {
    @Autowired
    private WeChatPayService weChatPayService;

    @PostMapping("/create-jsapi-order")
    public ResponseEntity<Map<String, String>> createJsapiOrder(@RequestBody PayRequest request) {
        String openid = getUserOpenidFromSessionOrToken(request.getToken());
        Map<String, String> result = weChatPayService.createJsapiOrder(openid, request.getOutTradeNo(), request.getTotalFee(), request.getBody());
        return ResponseEntity.ok(result);
    }

    @PostMapping("/notify")
    public ResponseEntity<String> handleNotify(@RequestBody String notifyData, HttpServletRequest request) {
        try {
            String signature = request.getHeader("Wechatpay-Signature");
            String nonce = request.getHeader("Wechatpay-Nonce");
            String timestamp = request.getHeader("Wechatpay-Timestamp");
            String body = notifyData;

            // 使用之前配置的 Verifier 来验证
            // boolean isValid = verifier.verify(timestamp, nonce, body, signature);

            // 解密通知数据 (APIv3 通知体是加密的)
            AesUtil aesUtil = new AesUtil(apiV3Key.getBytes(StandardCharsets.UTF_8));
            String plainText = aesUtil.decryptToString(nonce.getBytes(StandardCharsets.UTF_8), associatedData.getBytes(StandardCharsets.UTF_8), ciphertext.getBytes(StandardCharsets.UTF_8));

            JSONObject notifyDataObj = JSON.parseObject(plainText);
            String eventType = notifyDataObj.getString("event_type");
            JSONObject resource = notifyDataObj.getJSONObject("resource");
            String cipherText = resource.getString("ciphertext");
            String associatedData = resource.getString("associated_data");
            String nonceStr = resource.getString("nonce");

            String orderInfo = aesUtil.decryptToString(nonceStr.getBytes(), associatedData.getBytes(), cipherText.getBytes());
            JSONObject orderData = JSON.parseObject(orderInfo);
            String outTradeNo = orderData.getString("out_trade_no");
            String transactionId = orderData.getString("transaction_id");
            String tradeState = orderData.getString("trade_state");

            if ("SUCCESS".equals(tradeState)) {
                // TODO: 更新你的数据库订单状态为"已支付"
                // TODO: 执行发货、积分发放等后续业务逻辑
                // TODO: 记录日志
            } else if ("CLOSED".equals(tradeState) || "REVOKED".equals(tradeState)) {
                // 支付失败或关闭
            }

            return ResponseEntity.ok().body("{\"code\":\"SUCCESS\",\"message\":\"成功\"}");
        } catch (Exception e) {
            log.error("处理微信支付通知失败", e);
            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("");
        }
    }
}

工具类：

public class WeChatPayUtil {
    public static String sign(Map<String, String> params, String apiKey) {
        List<String> keys = new ArrayList<>(params.keySet());
        Collections.sort(keys);
        StringBuilder sb = new StringBuilder();
        for (String key : keys) {
            String value = params.get(key);
            if (value != null && !value.trim().isEmpty() && !"sign".equals(key)) {
                sb.append(key).append("=").append(value).append("&");
            }
        }
        sb.append("key=").append(apiKey);
        String stringA = sb.toString();
        String sign = DigestUtils.md5Hex(stringA).toUpperCase();
        return sign;
    }
}

总结

对接微信支付主要繁琐的是前期商户号、证书、配置，需仔细阅读文档，后续对接 SDK 非常简单，注意处理幂等性。