使用HttpUtil工具传递headers参数

可以用以下代码来传递headers参数：

import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Map;

public class HttpUtil {
    public static String sendGet(String urlString, Map<String, String> headers) throws IOException {
        URL url = new URL(urlString);
        HttpURLConnection con = (HttpURLConnection) url.openConnection();
        con.setRequestMethod("GET");

        if (headers != null) {
            for (Map.Entry<String, String> entry : headers.entrySet()) {
                con.setRequestProperty(entry.getKey(), entry.getValue());
            }
        }

        int responseCode = con.getResponseCode();
        if (responseCode == HttpURLConnection.HTTP_OK) {
            BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
            String inputLine;
            StringBuffer response = new StringBuffer();

            while ((inputLine = in.readLine()) != null) {
                response.append(inputLine);
            }
            in.close();
            return response.toString();
        } else {
            return "GET request failed with response code " + responseCode;
        }
    }
}

其中，headers参数在sendGet方法中传递，使用了for循环将其设置到HttpURLConnection的请求头部。