在java中无需打开浏览器即可检查url是否存在

Question

我想检查 url 是否存在，我在 java 中尝试使用以下代码，

public boolean exists(String URLName) {
    try {
         if (!URLName.toUpperCase().contains("HTTP")) 
             URLName="http://"+URLName;
             URL url = new URL(URLName);
             System.setProperty("java.net.useSystemProxies", "true");
             HttpURLConnection urlConn = (HttpURLConnection)  url.openConnection();
                 urlConn.setConnectTimeout(9000);
         urlConn.setReadTimeout(9000);            
          urlConn.connect();                    
                         if(HttpURLConnection.HTTP_OK == urlConn.getResponseCode())
             return true;
else
             return false;
  }
 catch (SocketTimeoutException e){
        return false;
   }

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

上面的代码在 Windows 中工作正常，但是当代码通过服务器（linux）运行时，我收到以下错误消息，

GConf Error: Failed to contact configuration server; some possible
causes are that you need to enable TCP/IP networking for ORBit, or
you have stale NFS locks due to a system crash. See
http://projects.gnome.org/gconf/ for information. (Details - 1:
Not running within active session)
GConf Error: Failed to contact configuration server; some possible
causes are that you need to enable TCP/IP networking for ORBit, or
you have stale NFS locks due to a system crash. See
http://projects.gnome.org/gconf/ for information. (Details - 1:
Not running within active session)
java.net.UnknownHostException: www.ep.gov
at
java.net.PlainSocketImpl.connect(PlainSocketImpl.j ava:177)
at
java.net.SocksSocketImpl.connect(SocksSocketImpl.j ava:366)
at java.net.Socket.connect(Socket.java:525)
at sun.net.NetworkClient.doConnect(NetworkClient.java :158)
at
sun.net.http://www.http.HttpClient.openServe...lient.java:394)
at
sun.net.http://www.http.HttpClient.openServe...lient.java:529)
at sun.net.www.http.HttpClient.<init>(HttpClient.java :233)
at sun.net.www.http.HttpClient.New(HttpClient.java:306)
at sun.net.www.http.HttpClient.New(HttpClient.java:323)
at
sun.net.http://www.protocol.http.HttpURLConn...ction.java:860)
at
sun.net.http://www.protocol.http.HttpURLConn...ction.java:801)
at
sun.net.http://www.protocol.http.HttpURLConn...ction.java:726)

我收到以下内容来自服务器管理员的消息

It is working, while it was run in X session (GUI Mode).
But it is not working in non-GUI mode. Please try to change the coding to make use of non-GUI mode." It seems the above code is making use of GUI mode. 

我需要一个备用代码来检查 url 是否存在而不使用 GUI。

问候 琳达

Answer 1

UnknownHostException 表示请求未到达其目的地。导致 Linux 服务器无法访问所需 URL www.ep.gov 的原因可能有很多。

请确保服务器可以访问 URL www.ep.gov。

Answer 2

我认为你的问题出在这一行：

System.setProperty("java.net.useSystemProxies", "true");

这似乎会导致系统尝试查找 Web 浏览器的 HTTP 代理配置，并最终遇到 Gnome 配置的一些问题。

您真的需要使用 HTTP 代理吗？如果没有，只需删除该行即可。如果您这样做，请阅读此页面了解如何配置代理。