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首先，讓我爲這篇文章的篇幅道歉，但主要是代碼，所以我希望你們都支持我！關於IUserType的NHibernate QueryOver
我有一個處理遺留數據庫的場景，我需要使用NHibernate 3.2編寫一個IUserType以獲取2個字符的「狀態」字段並從中返回一個布爾值。狀態字段可以包含3個可能的值：
* 'DI' // 'Disabled', return false
* ' ' // blank or NULL, return true
* NULL
這是我簡化了的內容。
表定義：
CREATE TABLE [dbo].[Client](
[clnID] [int] IDENTITY(1,1) NOT NULL,
[clnStatus] [char](2) NULL,
[clnComment] [varchar](250) NULL,
[clnDescription] [varchar](150) NULL,
[Version] [int] NOT NULL
)
流利的映射：
public class ClientMapping : CoreEntityMapping<Client>
{
public ClientMapping()
{
SchemaAction.All().Table("Client");
LazyLoad();
Id(x => x.Id, "clnId").GeneratedBy.Identity();
Version(x => x.Version).Column("Version").Generated.Never().UnsavedValue("0").Not.Nullable();
OptimisticLock.Version();
Map(x => x.Comment, "clnComment").Length(250).Nullable();
Map(x => x.Description, "clnDescription").Length(250).Nullable();
Map(x => x.IsActive, "clnStatus").Nullable().CustomType<StatusToBoolType>();
}
}
我IUserType實現：
public class StatusToBoolType : IUserType
{
public bool IsMutable { get { return false; } }
public Type ReturnedType { get { return typeof(bool); } }
public SqlType[] SqlTypes { get { return new[] { NHibernateUtil.String.SqlType }; } }
public object DeepCopy(object value)
{
return value;
}
public object Replace(object original, object target, object owner)
{
return original;
}
public object Assemble(object cached, object owner)
{
return cached;
}
public object Disassemble(object value)
{
return value;
}
public new bool Equals(object x, object y)
{
if (ReferenceEquals(x, y)) return true;
if (x == null || y == null) return false;
return x.Equals(y);
}
public int GetHashCode(object x)
{
return x == null ? typeof(bool).GetHashCode() + 473 : x.GetHashCode();
}
public object NullSafeGet(IDataReader rs, string[] names, object owner)
{
var obj = NHibernateUtil.String.NullSafeGet(rs, names[0]);
if (obj == null) return true;
var status = (string)obj;
if (status == " ") return true;
if (status == "DI") return false;
throw new Exception(string.Format("Expected data to be either empty or 'DI' but was '{0}'.", status));
}
public void NullSafeSet(IDbCommand cmd, object value, int index)
{
var parameter = ((IDataParameter) cmd.Parameters[index]);
var active = value == null || (bool) value;
if (active)
parameter.Value = " ";
else
parameter.Value = "DI";
}
}
但是這不起作用。該單元測試失敗，計數不準確。
[TestMethod]
public void GetAllActiveClientsTest()
{
//ACT
var count = Session.QueryOver<Client>()
.Where(x => x.IsActive)
.SelectList(l => l.SelectCount(x => x.Id))
.FutureValue<int>().Value;
//ASSERT
Assert.AreNotEqual(0, count);
Assert.AreEqual(1721, count);
}
失敗的原因是因爲它會生成以下SQL：
SELECT count(this_.clnID) as y0_ FROM Client this_ WHERE this_.clnstatus = @p0;
/* @p0 = ' ' [Type: String (0)] */
但我需要它，而不是產生這樣的：
SELECT count(this_.clnID) as y0_ FROM Client this_ WHERE (this_.clnstatus = @p0 <b> OR this_.clnstatus IS NULL);</b>
經過一番調試，我看到的是，NullSafeSet （）方法在生成查詢之前被調用，所以我能夠通過在該方法中編寫一些黑客代碼來操縱cmd.CommandText pro中的SQL perty。
...
public void NullSafeSet(IDbCommand cmd, object value, int index)
{
var parameter = ((IDataParameter) cmd.Parameters[index]);
var active = value == null || (bool) value;
if (active)
{
parameter.Value = " ";
if (cmd.CommandText.ToUpper().StartsWith("SELECT") == false) return;
var paramindex = cmd.CommandText.IndexOf(parameter.ParameterName);
if (paramindex > 0)
{
// Purpose: change [columnName] = @p0 ==> ([columnName] = @p0 OR [columnName] IS NULL)
paramindex += parameter.ParameterName.Length;
var before = cmd.CommandText.Substring(0, paramindex);
var after = cmd.CommandText.Substring(paramindex);
//look at the text before the '= @p0' and find the column name...
var columnSection = before.Split(new[] {"= " + parameter.ParameterName}, StringSplitOptions.RemoveEmptyEntries).Reverse().First();
var column = columnSection.Substring(columnSection.Trim().LastIndexOf(' ')).Replace("(", "");
var myCommand = string.Format("({0} = {1} OR {0} IS NULL)", column.Trim(), parameter.ParameterName);
paramindex -= (parameter.ParameterName.Length + column.Length + 1);
var orig = before.Substring(0, paramindex);
cmd.CommandText = orig + myCommand + after;
}
}
else
parameter.Value = "DI";
}
但是這是NHibernate！像這樣篡改sql語句不可能是解決這個問題的正確方法嗎？對？
因爲它是一個共享的遺留數據庫，所以我不能將表格模式更改爲NOT NULL，否則我會這樣做，並避免這種情況。
所以最後，在所有這個前奏我的問題是這樣的，我可以在哪裏告訴NHibernate生成一個自定義的SQL條件語句爲這個IUserType？
謝謝大家提前！