生成对接支付渠道的Java 代码

好的，以下是一个简单的对接支付渠道的Java代码示例：

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.security.MessageDigest;
import java.util.Iterator;
import java.util.Map;
import java.util.TreeMap;

public class PaymentChannel {

    private static final String PAYMENT_API_URL = "https://example.com/payment";

    private static final String API_KEY = "your_api_key";
    private static final String API_SECRET = "your_api_secret";

    public static void main(String[] args) {
        // 构建请求参数
        TreeMap<String, String> params = new TreeMap<String, String>();
        params.put("amount", "100.00");
        params.put("currency", "CNY");
        params.put("description", "Test Payment");
        params.put("merchant_id", "123456");
        params.put("notify_url", "https://example.com/notify");
        params.put("return_url", "https://example.com/return");
        params.put("timestamp", String.valueOf(System.currentTimeMillis() / 1000));
        params.put("nonce_str", String.valueOf(System.currentTimeMillis()));

        String sign = generateSign(params);
        params.put("sign", sign);

        // 发送请求
        String response = sendRequest(params);

        // 处理响应
        System.out.println(response);
    }

    private static String generateSign(Map<String, String> params) {
        StringBuilder builder = new StringBuilder();
        Iterator<Map.Entry<String, String>> iterator = params.entrySet().iterator();
        while (iterator.hasNext()) {
            Map.Entry<String, String> entry = iterator.next();
            builder.append(entry.getKey()).append("=").append(entry.getValue());
            if (iterator.hasNext()) {
                builder.append("&");
            }
        }
        builder.append(API_SECRET);
        String sign = md5(builder.toString());
        return sign;
    }

    private static String md5(String text) {
        try {
            MessageDigest md5 = MessageDigest.getInstance("MD5");
            byte[] md5Bytes = md5.digest(text.getBytes("UTF-8"));
            StringBuilder builder = new StringBuilder();
            for (byte md5Byte : md5Bytes) {
                builder.append(String.format("%02x", md5Byte & 0xff));
            }
            return builder.toString();
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    private static String sendRequest(Map<String, String> params) {
        HttpURLConnection connection = null;
        BufferedReader reader = null;
        try {
            StringBuilder builder = new StringBuilder();
            Iterator<Map.Entry<String, String>> iterator = params.entrySet().iterator();
            while (iterator.hasNext()) {
                Map.Entry<String, String> entry = iterator.next();
                builder.append(entry.getKey()).append("=").append(URLEncoder.encode(entry.getValue(), "UTF-8"));
                if (iterator.hasNext()) {
                    builder.append("&");
                }
            }
            String query = builder.toString();

            URL url = new URL(PAYMENT_API_URL + "?" + query);
            connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");
            connection.setConnectTimeout(5000);
            connection.setReadTimeout(5000);

            reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            StringBuilder responseBuilder = new StringBuilder();
            String line;
            while ((line = reader.readLine()) != null) {
                responseBuilder.append(line);
            }
            return responseBuilder.toString();
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        } finally {
            if (connection != null) {
                connection.disconnect();
            }
            if (reader != null) {
                try {
                    reader.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

在这个示例中，我们使用了Java的HttpURLConnection类来发送HTTP请求，使用TreeMap来保证请求参数按字典序排序，使用MD5算法生成签名。你可以根据你所使用的支付渠道的API文档来修改这个示例代码，以符合你所使用的支付渠道的要求。