连接到MongoDB数据库时Android中的java.io.IOException

Question

在我的Android应用程序中，当我与数据库建立连接时，我收到java.io.IOException。请告诉我这是什么问题？

代码：

public void connect_to_db() {
    try {
        URL requestUrl = new URL("url for MongoDB database");
        HttpURLConnection connection = (HttpURLConnection) requestUrl.openConnection();
        connection.setRequestProperty("Accept-Encoding", "identity");
        connection.connect();
    }
    catch(Exception exp) {
        Log.e("TAG","Exception",exp);
    }
}

错误：

05-09 03:07:22.711 2962-2962/com.example.abc.project1 E/TAG: Exception
                                                            java.io.IOException
at libcore.net.http.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:87)
at libcore.net.http.HttpsURLConnectionImpl.connect(HttpsURLConnectionImpl.java:165)
at com.example.abc.project1.LocationDetector.connect_to_db(LocationDetector.java:85)
at com.example.abc.project1.LocationDetector.onLocationChanged(LocationDetector.java:37)
at android.location.LocationManager$ListenerTransport._handleMessage(LocationManager.java:257)
at android.location.LocationManager$ListenerTransport.access$000(LocationManager.java:186)
at android.location.LocationManager$ListenerTransport$1.handleMessage(LocationManager.java:202)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5410)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
at dalvik.system.NativeStart.main(Native Method)