java - URLConnection，找不到符号

Question

我正在尝试使用以下代码获取标题字段：

import java.net.URL;
import java.net.URLConnection;
 
public class Main {

  public static void main() {

   try {

    URL url = new URL("URL");
    URLConnection con = url.openConnection();
    con.setRequestMethod("HEAD");
    con.setRequestProperty("property", "name");

    System.out.println("\nGetting Response Header By Key ...\n");
    String userToken = con.getHeaderField("parameter");

    if (userToken == null) {
        System.out.println("Key 'userToken' is not found!");
    } else {
        System.out.println("userToken - " + userToken);
     
     
    }

    System.out.println("\n Done");

    } catch (Exception e) {
       e.printStackTrace();
    }

  }
}

但我收到以下错误：

Main.java:14: 错误：找不到符号 con.setRequestMethod("HEAD"); ^ 符号：方法 setRequestMethod(String) 位置：URLConnection 类型的变量 con 1 错误

标签： javasymbolsheadurlconnection

Answer 1

您正在尝试对变量使用HttpURLConnection.setRequestMethod ( String) 。URLConnection幸运的是，url.openConnection();实际上会返回 a HttpURLConnection，因此您可以转换为HttpURLConnection：

HttpURLConnection con = (HttpURLConnection) url.openConnection();
con.setRequestMethod("HEAD");