三層式系統架構－商業邏輯層

2009-11-17

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多層架構

三層式系統架構－商業邏輯層

此介紹商業邏輯層需要的程式碼，

我個人對於商業邏輯層的定義為一個Tabel對映一個類別，

此類別需定義出Table的各欄位屬性，

及關於此Table的查詢、新增、修改、刪除等資料操作函式，

舉例

有一Table如下

欄位名稱	資料型態
CustomerID	Varchar(10)
CompanyName	Varchar(50)

0.類別名稱


End Class

1.定義私有變數


   Private _CompanyName As String = ""

2.定義全域屬性


      Get
         Return _CustomerID
      End Get
      Set(ByVal value As String)
         _CustomerID = value
      End Set
   End Property

   Public Property CompanyName() As String
      Get
         Return _CompanyName
      End Get
      Set(ByVal value As String)
         _CompanyName = value
      End Set
   End Property

3.建立清除函式


      _CustomerID = ""
      _CompanyName = ""
   End Sub

4.建立New函式


      Clear()
   End Sub

5.定義查詢、新增、修改、刪除資料操作


      Try
         Return dalCustomers.GetData
      Catch ex As Exception
         Throw New Exception(ex.Message)
      End Try
   End Function

   Public Function Insert() As Integer
      Try
         Return dalCustomers.Insert(Me)
      Catch ex As Exception
         Throw New Exception(ex.Message)
      End Try
   End Function

   Public Function Update() As Integer
      Try
         Return dalCustomers.Update(Me)
      Catch ex As Exception
         Throw New Exception(ex.Message)
      End Try
   End Function

   Public Shared Function Delete(ByVal Code As String) As Integer
      Try
         Return dalCustomers.Delete(Code)
      Catch ex As Exception
         Throw New Exception(ex.Message)
      End Try
   End Function

6.查詢資料使用物件回傳(非必要，個人使用方式)

GetCustomers函式會回傳一個bllCustomers陣列物件，

此用法為在使用欄位時是可以用屬性的方式取得值


      Me.Clear()
      If DT.Rows.Count > 0 Then
         CustomerID = DT.Rows(0).Item("customerid").ToString
         CompanyName = DT.Rows(0).Item("companyname").ToString
      End If
   End Sub

   Public Shared Sub SetData(ByVal DT As DataTable, ByRef Data() As bllCustomers)
      If DT.Rows.Count > 0 Then
         For i As Integer = 0 To DT.Rows.Count - 1
            If Data Is Nothing Then
               ReDim Data(0)
            Else
               ReDim Data(Data.Length)
            End If
            Data(UBound(Data)) = New bllCustomers
            Data(UBound(Data)).CustomerID = DT.Rows(i).Item("customerid").ToString
            Data(UBound(Data)).CompanyName = DT.Rows(i).Item("companyname").ToString
         Next
      End If
   End Sub

   Public Shared Function GetCustomers() As bllCustomers()
      Try
         Dim tmCustomers() As bllCustomers = Nothing
         Dim DT As DataTable = dalCustomers.GetData
         SetData(DT, tmCustomers)
         Return tmCustomers
      Catch ex As Exception
         Throw New Exception(ex.Message)
      End Try
   End Function

創建一個商業邏輯層有很多程式碼其實是相似的，

故可以使用CodeSmith等軟體來產生相關程式碼，

再稍做修正，才不會浪費大量的時間。

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