我在ASP.NET MVC中有一个控制器方法，如下所示：
Exception in thread "main" java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.spark.deploy.worker.DriverWrapper$.main(DriverWrapper.scala:58)
at org.apache.spark.deploy.worker.DriverWrapper.main(DriverWrapper.scala)
Caused by: java.io.IOException: Failed to open native connection to Cassandra at {127.0.1.1}:9042
at com.datastax.spark.connector.cql.CassandraConnector$.com$datastax$spark$connector$cql$CassandraConnector$$createSession(CassandraConnector.scala:163)
at com.datastax.spark.connector.cql.CassandraConnector$$anonfun$3.apply(CassandraConnector.scala:149)
at com.datastax.spark.connector.cql.CassandraConnector$$anonfun$3.apply(CassandraConnector.scala:149)
at com.datastax.spark.connector.cql.RefCountedCache.createNewValueAndKeys(RefCountedCache.scala:31)
at com.datastax.spark.connector.cql.RefCountedCache.acquire(RefCountedCache.scala:56)
at com.datastax.spark.connector.cql.CassandraConnector.openSession(CassandraConnector.scala:82)
at com.datastax.spark.connector.cql.CassandraConnector.withSessionDo(CassandraConnector.scala:110)
at com.datastax.spark.connector.cql.CassandraConnector.withClusterDo(CassandraConnector.scala:121)
at com.datastax.spark.connector.cql.Schema$.fromCassandra(Schema.scala:322)
at com.datastax.spark.connector.cql.Schema$.tableFromCassandra(Schema.scala:342)
at com.datastax.spark.connector.rdd.CassandraTableRowReaderProvider$class.tableDef(CassandraTableRowReaderProvider.scala:50)
at com.datastax.spark.connector.rdd.CassandraTableScanRDD.tableDef$lzycompute(CassandraTableScanRDD.scala:60)
at com.datastax.spark.connector.rdd.CassandraTableScanRDD.tableDef(CassandraTableScanRDD.scala:60)
at com.datastax.spark.connector.rdd.CassandraTableRowReaderProvider$class.verify(CassandraTableRowReaderProvider.scala:137)
at com.datastax.spark.connector.rdd.CassandraTableScanRDD.verify(CassandraTableScanRDD.scala:60)
at com.datastax.spark.connector.rdd.CassandraTableScanRDD.getPartitions(CassandraTableScanRDD.scala:232)
at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:248)
at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:246)
at scala.Option.getOrElse(Option.scala:121)
at org.apache.spark.rdd.RDD.partitions(RDD.scala:246)
at org.apache.spark.rdd.RDD$$anonfun$distinct$2.apply(RDD.scala:401)
at org.apache.spark.rdd.RDD$$anonfun$distinct$2.apply(RDD.scala:401)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:112)
at org.apache.spark.rdd.RDD.withScope(RDD.scala:358)
at org.apache.spark.rdd.RDD.distinct(RDD.scala:400)
at com.access_company.twine.OnlineGatewayCount$.main(OnlineGatewayCount.scala:93)
at com.access_company.twine.OnlineGatewayCount.main(OnlineGatewayCount.scala)
... 6 more
Caused by: com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (tried: /127.0.1.1:9042 (com.datastax.driver.core.exceptions.TransportException: [/127.0.1.1] Cannot connect))
at com.datastax.driver.core.ControlConnection.reconnectInternal(ControlConnection.java:233)
at com.datastax.driver.core.ControlConnection.connect(ControlConnection.java:79)
at com.datastax.driver.core.Cluster$Manager.init(Cluster.java:1424)
at com.datastax.driver.core.Cluster.getMetadata(Cluster.java:403)
at com.datastax.spark.connector.cql.CassandraConnector$.com$datastax$spark$connector$cql$CassandraConnector$$createSession(CassandraConnector.scala:156)
此方法的路由如下所示：
public class HomeController : Controller
{
SessionHelper mysession = new SessionHelper();
[HttpGet]
[ActionName("Index")]
public ActionResult Index_Get(SessionHelper arg)
{
pageload();
if (Request["hid"] != null)
{
mysession.HotelID = Request["hid"];
}
else
{
mysession.HotelID = mysession.HotelID;
//if HotelID==null i want to get the value to querystring i do it like this but did not worked
}
if (Request["Culture"] != null)
{
mysession.Culture = Request["Culture"];
}
else
{
mysession.Culture = mysession.Culture;
//if Culture ==null i want to get the value to querystring i do it like this but did not worked
}
return View(mysession);
}
}
我有session-helper类这个类我用来设置默认值并存储查询字符串参数的更改值，如果它们没有传递值：
routes.MapRoute(
"OpenCase",
"IBE/hid={hid}",
new { controller = "Home", action = "Index" }
);
用户将使用以下网址：
public class SessionHelper
{
public SessionHelper()
{
// ------ Set default values here
Rate = "";
HotelID = string.Empty;
CSS_FileName = "default.css";
Culture = "En";
Checkin = DateTime.Today.Date;
Checkout = DateTime.Today.Date.AddDays(1);
//Maximum numbers
MaximumNumberOfRooms = 4;
MaximumNumberOfAdultsPerRoom = 4;
MaximumNumberOfChildrenPerRoom = 3;
MaximumDaysAheadBookable = 450;
MaximumDaysBetweenCheckinCheckout = 31;
}
#region String properties
public string Rate
{
get { return HttpContext.Current.Session["Rate"] as string; }
set { HttpContext.Current.Session["Rate"] = value; }
}
public string CSS_FileName
{
get { return HttpContext.Current.Session["CSS_FileName"] as string; }
set { HttpContext.Current.Session["CSS_FileName"] = value; }
}
public string Culture
{
get { return HttpContext.Current.Session["Culture"] as string; }
set { HttpContext.Current.Session["Culture"] = value; }
}
#endregion
#region Integer properties
public string HotelID
{
get { return (string)(HttpContext.Current.Session["HotelID"]); }
set { HttpContext.Current.Session["HotelID"] = value; }
}
//Maximum numbers defaulot value
public int MaximumNumberOfRooms
{
get { return (int)(HttpContext.Current.Session["MaximumNumberOfRooms"]); }
set { HttpContext.Current.Session["MaximumNumberOfRooms"] = value; }
}
public int MaximumNumberOfAdultsPerRoom
{
get { return (int)(HttpContext.Current.Session["MaximumNumberOfAdultsPerRoom"]); }
set { HttpContext.Current.Session["MaximumNumberOfAdultsPerRoom"] = value; }
}
public int MaximumNumberOfChildrenPerRoom
{
get { return (int)(HttpContext.Current.Session["MaximumNumberOfChildrenPerRoom"]); }
set { HttpContext.Current.Session["MaximumNumberOfChildrenPerRoom"] = value; }
}
public int MaximumDaysAheadBookable
{
get { return (int)(HttpContext.Current.Session["MaximumDaysAheadBookable"]); }
set { HttpContext.Current.Session["MaximumDaysAheadBookable"] = value; }
}
public int MaximumDaysBetweenCheckinCheckout
{
get { return (int)(HttpContext.Current.Session["MaximumDaysBetweenCheckinCheckout"]); }
set { HttpContext.Current.Session["MaximumDaysBetweenCheckinCheckout"] = value; }
}
#endregion
#region Date properties
public DateTime Checkin
{
get { return (DateTime)(HttpContext.Current.Session["Checkin"]); }
set { HttpContext.Current.Session["Checkin"] = value; }
}
public DateTime Checkout
{
get { return (DateTime)(HttpContext.Current.Session["Checkout"]); }
set { HttpContext.Current.Session["Checkout"] = value; }
}
#endregion
但是，我想更改查询字符串参数值，如果用户没有传递query-string参数的值，则查询字符串设置默认值例如，如果用户获取这样的url：
没有任何值的 http://localhost:51518/IBE/hid=100?Culture=Fr&Rate=ibe
我想从http://localhost:51518/IBE/hid=?Culture=&Rate= class
答案 0 :(得分：1)
嗯，首先，这不是你如何设置默认值。只有在未使用不同的值初始化类时，构造函数中设置的值才会适用。你的问题是模型绑定器确实会用null值初始化这个类，这实际上否定了你在构造函数中所做的事情。
为属性设置默认值的正确方法是使用自定义getter和setter：
private string culture;
public string Culture
{
get { return culture ?? "En"; }
set { culture = value; }
}
或者，如果您可以使用C＃6 +：
public string Culture { get; set; } = "En";
该代码与前一代码具有相同的效果，但显然更容易。无论哪种方式，这里的要点是该属性将返回默认值＆＃34; En＆＃34;，只要它未设置（即为空）。然后，即使您的类使用空值初始化，仍将返回默认值。
此外，如下所示的行是没有意义的：
mysession.HotelID = mysession.HotelID;
您将变量设置为变量的当前值，这没有任何意义。它已经具有该值。假设您如上所述正确实施了默认值，那么您就可以摆脱所有else条件。