Как я возвращаю значение к sqldatareader, если значение является нулевым?
Как Вы добавляете свои классы Weblogic к пути к классу в Eclipse? Вы используете WTP и время выполнения сервера? Если так, Ваше время выполнения сервера связано с Вашим проектом?
, Если Вы щелкаете правой кнопкой по своему проекту и выбираете сборку path->configure путь сборки и затем выбираете вкладку библиотек. Необходимо видеть weblogic библиотеки, связанные здесь. Если Вы не делаете можно нажать Add Library->Server Runtime. Если библиотека не там, то сначала необходимо настроить ее. Windows->Preferences->Server->Installed runtimes
4 ответа
You can check whether or not a given ordinal position is null using .IsDBNull() and then do something - e.g. set your value to -1 or something:
int myOrdinal = myReader.GetOrdinal("Truthfullness");
if(myReader.IsDBNull(myOrdinal))
{
theArticle.Truthfulness = -1;
}
else
{
theArticle.Truthfulness = myReader.GetInt32(myOrdinal);
}
As Mike Hofer points out in his answer, you could also wrap all this logic into an extension method:
public static class SqlDataReaderExtensions
{
public static int SafeGetInt32(this SqlDataReader reader,
string columnName, int defaultValue)
{
int ordinal = reader.GetOrdinal(columnName);
if(!reader.IsDbNull(ordinal))
{
return reader.GetInt32(ordinal);
}
else
{
return defaultValue;
}
}
}
and then just use that "SafeGetInt32" method instead:
theArticle.Truthfulness = myReader.SafeGetInt32("Truthfullness", -1);
Marc
Did you check, SqlDataReader.IsDBNull Method? Probably something like:
if(myReader.IsDBNull(myReader.GetOrdinal("Truthfulness"))
theArticle.Truthfulness = string.Empty;
else
theArticle.Truthfulness = ((myReader.GetInt32(myReader.GetOrdinal("Truthfulness"))))
You know, I deal with this all the time in Oracle. To clean the code up, I wrote a set of extension methods to simplify the operation:
using System.Data.OracleClient;
public static class OracleDataReaderExtensions
{
public static int GetInt32(this OracleDataReader reader, string columnName, int defaultValue)
{
return reader.GetInt32(reader.GetOrdinal(columnName)) != DbNull.Value ?
reader.GetInt32(reader.GetOrdinal(columnName)) :
defaultValue;
}
}
Create a separate overload for each type you want to return. I primarily work with string, int, date, and decimal. Remember YAGNI (you don't need to work with every type supported by the reader, only those you actually use.)
An extension class like this for SQL Server is really easy to write, and will VASTLY simplify your work. Trust me on that. Would I lie to you? :)
Вот то, что мы используем на SQLServer, и это прекрасно работает:
...
Dim X as Object = pbDr("TotAmt") 'dr is dim'ed as a DataReader
...
Public Function pbDr(ByVal drName As String) As Object
Dim SQLError As SqlClient.SqlException
Dim IsNull As Boolean
Dim Ordinal, DispNbr As Integer
Try
Ordinal = dr.GetOrdinal(drName)
IsNull = dr.IsDBNull(Ordinal)
If IsNull Then
Dim Dbtype As String = dr.GetFieldType(Ordinal).ToString
If Dbtype = "System.String" Then
Return ""
ElseIf Dbtype = "System.Int32" _
OrElse Dbtype = "System.Double" _
OrElse Dbtype = "System.Decimal" _
OrElse Dbtype = "System.Int16" Then
Return 0
Else
MsgBox("Print This Screen And Send To Support" _
& "pbdr-Object = " & Dbtype, MsgBoxStyle.Critical)
Return ""
End If
Else
Return dr(Ordinal)
End If
Catch sqlerror
Call DispSQLError(SQLError, "pbDr")
pbDr = ""
End Try
End Function