HttpURLConnection超时设置

如果要用5秒钟以上的时间来连接URL，我想返回false-使用Java怎么可能？这是我用来检查URL是否有效的代码

HttpURLConnection.setFollowRedirects(false);
HttpURLConnection con = (HttpURLConnection) new URL(url).openConnection();
con.setRequestMethod("HEAD");
return (con.getResponseCode() == HttpURLConnection.HTTP_OK);

HttpURLConnection有一个setConnectTimeout方法。

只需将超时设置为5000毫秒，然后捕获 java.net.SocketTimeoutException

您的代码应如下所示：

try {
   HttpURLConnection.setFollowRedirects(false);
   HttpURLConnection con = (HttpURLConnection) new URL(url).openConnection();
   con.setRequestMethod("HEAD");

   con.setConnectTimeout(5000); //set timeout to 5 seconds

   return (con.getResponseCode() == HttpURLConnection.HTTP_OK);
} catch (java.net.SocketTimeoutException e) {
   return false;
} catch (java.io.IOException e) {
   return false;
}

您可以这样设置超时时间，

con.setConnectTimeout(connectTimeout);
con.setReadTimeout(socketTimeout);

如果HTTP连接没有超时，则可以在后台线程本身（AsyncTask，Service等）中实现超时检查器，以下类是Customize AsyncTask的示例，该示例在特定时间段后超时

public abstract class AsyncTaskWithTimer<Params, Progress, Result> extends
    AsyncTask<Params, Progress, Result> {

private static final int HTTP_REQUEST_TIMEOUT = 30000;

@Override
protected Result doInBackground(Params... params) {
    createTimeoutListener();
    return doInBackgroundImpl(params);
}

private void createTimeoutListener() {
    Thread timeout = new Thread() {
        public void run() {
            Looper.prepare();

            final Handler handler = new Handler();
            handler.postDelayed(new Runnable() {
                @Override
                public void run() {

                    if (AsyncTaskWithTimer.this != null
                            && AsyncTaskWithTimer.this.getStatus() != Status.FINISHED)
                        AsyncTaskWithTimer.this.cancel(true);
                    handler.removeCallbacks(this);
                    Looper.myLooper().quit();
                }
            }, HTTP_REQUEST_TIMEOUT);

            Looper.loop();
        }
    };
    timeout.start();
}

abstract protected Result doInBackgroundImpl(Params... params);
}

一个样品

public class AsyncTaskWithTimerSample extends AsyncTaskWithTimer<Void, Void, Void> {

    @Override
    protected void onCancelled(Void void) {
        Log.d(TAG, "Async Task onCancelled With Result");
        super.onCancelled(result);
    }

    @Override
    protected void onCancelled() {
        Log.d(TAG, "Async Task onCancelled");
        super.onCancelled();
    }

    @Override
    protected Void doInBackgroundImpl(Void... params) {
        // Do background work
        return null;
    };
 }

我可以通过添加简单的行来获得针对此类类似问题的解决方案

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

我的要求是知道响应代码，为此，仅获取元信息就足够了，而不是获取完整的响应正文。

默认的请求方法是GET，这要花很多时间才能返回，最终使我抛出SocketTimeoutException。当我将Request Method设置为HEAD时，响应速度非常快。