Java java.net包HTTP请求中错误响应体的正确处理

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.util.Map;

// 假设这里有一个日志记录器，例如使用SLF4J
// import org.slf4j.Logger;
// import org.slf4j.LoggerFactory;

public class HttpConnectionHandler {

    // private static final Logger log = LoggerFactory.getLogger(HttpConnectionHandler.class);

    /**
     * 发送HTTP POST请求并获取响应体，包括错误响应的响应体。
     *
     * @param requestUrl       请求的URL
     * @param payload          请求体内容
     * @param requestProperties 请求头属性
     * @return 服务器返回的响应体字符串
     */
    public static String sendPostRequest(String requestUrl, String payload, Map<String, String> requestProperties) {
        StringBuilder responseBody = new StringBuilder();
        HttpURLConnection connection = null;
        try {
            URL url = new URL(requestUrl);
            connection = (HttpURLConnection) url.openConnection();

            // 配置连接
            connection.setDoInput(true);
            connection.setDoOutput(true);
            connection.setRequestMethod("POST");
            connection.setConnectTimeout(5000); // 设置连接超时时间，单位毫秒
            connection.setReadTimeout(5000);    // 设置读取超时时间，单位毫秒

            // 设置请求头属性
            if (requestProperties != null) {
                for (Map.Entry<String, String> entry : requestProperties.entrySet()) {
                    connection.setRequestProperty(entry.getKey(), entry.getValue());
                }
            }
            // 默认设置Content-Type为application/json，如果payload是JSON格式
            if (!requestProperties.containsKey("Content-Type")) {
                 connection.setRequestProperty("Content-Type", "application/json");
            }


            // 写入请求体
            try (OutputStreamWriter writer = new OutputStreamWriter(connection.getOutputStream(), StandardCharsets.UTF_8)) {
                writer.write(payload);
                writer.flush(); // 确保所有数据都已写入输出流
            }

            // 获取响应状态码
            int responseCode = connection.getResponseCode();
            // log.info("请求URL: {}, 响应状态码: {}", requestUrl, responseCode); // 记录响应码

            InputStream inputStream;
            // 根据响应码选择正确的输入流
            if (responseCode >= HttpURLConnection.HTTP_BAD_REQUEST) { // 400及以上为错误响应
                inputStream = connection.getErrorStream();
                // log.warn("检测到错误响应，状态码: {}, URL: {}", responseCode, requestUrl);
            } else {
                inputStream = connection.getInputStream();
            }

            // 读取响应体
            if (inputStream != null) { // 确保流不为空
                try (BufferedReader br = new BufferedReader(new InputStreamReader(inputStream, StandardCharsets.UTF_8))) {
                    String line;
                    while ((line = br.readLine()) != null) {
                        responseBody.append(line);
                    }
                }
            } else {
                // 极少数情况下，如果既没有正常输入流也没有错误流，可能发生
                // log.warn("无法获取到URL: {} 的输入流，状态码: {}", requestUrl, responseCode);
            }

        } catch (Exception e) {
            // log.error("HTTP请求到 {} 发生错误: {}", requestUrl, e.getMessage(), e);
            System.err.println("HTTP请求到 " + requestUrl + " 发生错误: " + e.getMessage());
            // 可以在这里选择抛出自定义异常，或者返回一个特定的错误指示符
        } finally {
            if (connection != null) {
                connection.disconnect(); // 关闭HTTP连接
            }
        }
        return responseBody.toString();
    }
}