java微信支付后端代码

以下是使用Java实现微信支付后端代码的示例：

1. 创建统一下单请求对象

public class UnifiedOrderRequest {
    private String appid; // 公众账号ID
    private String mch_id; // 商户号
    private String nonce_str; // 随机字符串
    private String body; // 商品描述
    private String out_trade_no; // 商户订单号
    private int total_fee; // 标价金额，单位为分
    private String spbill_create_ip; // 终端IP
    private String notify_url; // 通知地址
    private String trade_type; // 交易类型
    private String openid; // 用户标识

    // 省略 getter 和 setter 方法
}

2. 创建统一下单响应对象

public class UnifiedOrderResponse {
    private String return_code; // 返回状态码
    private String return_msg; // 返回信息
    private String appid; // 公众账号ID
    private String mch_id; // 商户号
    private String nonce_str; // 随机字符串
    private String sign; // 签名
    private String result_code; // 业务结果
    private String prepay_id; // 预支付交易会话标识
    private String trade_type; // 交易类型
    private String code_url; // 二维码链接

    // 省略 getter 和 setter 方法
}

3. 发送统一下单请求

public class WechatPayService {

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

    public UnifiedOrderResponse unifiedOrder(UnifiedOrderRequest request) throws Exception {
        String xml = buildUnifiedOrderXml(request);
        String responseXml = postXml(UNIFIED_ORDER_URL, xml);
        return parseUnifiedOrderXml(responseXml);
    }

    private String buildUnifiedOrderXml(UnifiedOrderRequest request) throws Exception {
        Map<String, Object> data = new HashMap<>();
        data.put("appid", request.getAppid());
        data.put("mch_id", request.getMch_id());
        data.put("nonce_str", request.getNonce_str());
        data.put("body", request.getBody());
        data.put("out_trade_no", request.getOut_trade_no());
        data.put("total_fee", request.getTotal_fee());
        data.put("spbill_create_ip", request.getSpbill_create_ip());
        data.put("notify_url", request.getNotify_url());
        data.put("trade_type", request.getTrade_type());
        data.put("openid", request.getOpenid());
        data.put("sign", WechatPayUtil.sign(data, "商户密钥"));

        return WechatPayUtil.mapToXml(data);
    }

    private UnifiedOrderResponse parseUnifiedOrderXml(String xml) throws Exception {
        Map<String, String> data = WechatPayUtil.xmlToMap(xml);
        UnifiedOrderResponse response = new UnifiedOrderResponse();
        response.setReturn_code(data.get("return_code"));
        response.setReturn_msg(data.get("return_msg"));
        response.setAppid(data.get("appid"));
        response.setMch_id(data.get("mch_id"));
        response.setNonce_str(data.get("nonce_str"));
        response.setSign(data.get("sign"));
        response.setResult_code(data.get("result_code"));
        response.setPrepay_id(data.get("prepay_id"));
        response.setTrade_type(data.get("trade_type"));
        response.setCode_url(data.get("code_url"));

        return response;
    }

    private String postXml(String url, String xml) throws Exception {
        HttpClient httpClient = HttpClients.createDefault();
        HttpPost httpPost = new HttpPost(url);
        httpPost.setEntity(new StringEntity(xml, ContentType.APPLICATION_XML));

        HttpResponse response = httpClient.execute(httpPost);
        HttpEntity entity = response.getEntity();
        String responseXml = EntityUtils.toString(entity);
        EntityUtils.consume(entity);

        return responseXml;
    }
}

4. 处理支付结果通知

public class WechatPayNotifyService {

    public void handleNotify(HttpServletRequest request, HttpServletResponse response, String merchantKey) throws Exception {
        String xml = IOUtils.toString(request.getInputStream(), StandardCharsets.UTF_8);
        Map<String, String> data = WechatPayUtil.xmlToMap(xml);

        if (WechatPayUtil.verifySign(data, merchantKey)) {
            if ("SUCCESS".equals(data.get("return_code")) && "SUCCESS".equals(data.get("result_code"))) {
                // 支付成功，处理业务逻辑
            }
            String responseXml = buildNotifyResponseXml("SUCCESS", "OK");
            response.getWriter().write(responseXml);
        } else {
            String responseXml = buildNotifyResponseXml("FAIL", "签名验证失败");
            response.getWriter().write(responseXml);
        }
    }

    private String buildNotifyResponseXml(String returnCode, String returnMsg) {
        Map<String, String> data = new HashMap<>();
        data.put("return_code", returnCode);
        data.put("return_msg", returnMsg);
        return WechatPayUtil.mapToXml(data);
    }
}

以上代码仅为示例，实际使用时需要根据具体业务需求进行适当调整。同时，为了确保交易的安全性，建议使用 HTTPS 协议进行通信，并对敏感信息进行加密处理。