机房重构之模板方法模式

    在设计模式讲课之后，对模板方法模式有了更深的理解！这次机房重构的时候，用模板方法模式也是比较顺手的！

    机房系统的三个地方都需要用到模板方法！

    一：

   二：

   第三个地方就是大家都会想到的---组合查询，在这就不上图了！

   组合查询时这三个中最难、最复杂的，那就以组合查询为例，给大家介绍一下我是如何使用模板方法的！

   首先，手动建一个Windows窗体，作为父窗体；之后，添加对应的子窗体！

    添加子窗体的方法：添加---选择“继承的窗体”---确定---弹出第二张图---选择对应的其父窗体即可。

   下面给大家展示一下我的代码：

   U层：父窗体时用来写所有子窗体的相同部分和被子窗体重写的方法（也就是不同的部分，不同的部分只写一个框架）！那就思考一下组合查询中相同的部分是什么？什么方法需要被子类重写？

   相同的部分包括：相同的属性，相同的判断，还有一个公用的实体。被子类重写的方法包括：查询时非公共的部分，得到数据库表名（每个子窗体应用到数据库中的表示不同的），将组合查询中的字段名转化成英文。

<span style="font-size:18px;">Private Sub FrmGroupQuery_Load(sender As Object, e As EventArgs) Handles MyBase.Load</span>

<span style="font-size:18px;">        '写出公共部分
        cmbOperA.Items.Add("=")
        cmbOperA.Items.Add("<")
        cmbOperA.Items.Add(">")
        cmbOperA.Items.Add("<>")

        cmbOperB.Items.Add("=")
        cmbOperB.Items.Add("<")
        cmbOperB.Items.Add(">")
        cmbOperB.Items.Add("<>")

        cmbOperC.Items.Add("=")
        cmbOperC.Items.Add("<")
        cmbOperC.Items.Add(">")
        cmbOperC.Items.Add("<>")

        cmbRelationA.Items.Add("与")
        cmbRelationA.Items.Add("或")

        cmbRelationB.Items.Add("与")
        cmbRelationB.Items.Add("或")

        '窗体加载后，默认后两组选项不能用
        cmbFieldB.Enabled = False
        cmbOperB.Enabled = False
        txtContentB.Enabled = False
        cmbRelationB.Enabled = False

        cmbFieldC.Enabled = False
        cmbOperC.Enabled = False
        txtContentC.Enabled = False
    End Sub

    '第一个关系不为空
    Private Sub cmbRelationA_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cmbRelationA.SelectedIndexChanged
        cmbFieldB.Enabled = True
        cmbOperB.Enabled = True
        txtContentB.Enabled = True
        cmbRelationB.Enabled = True
    End Sub

    '第二个关系不为空
    Private Sub cmbRelationB_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cmbRelationB.SelectedIndexChanged
        cmbFieldC.Enabled = True
        cmbOperC.Enabled = True
        txtContentC.Enabled = True
    End Sub


    '单击查询执行的共同操作
    Private Sub btnQuery_Click(sender As Object, e As EventArgs) Handles btnQuery.Click

        '首先第一组选项不能为空
        If cmbRelationA.Text = "" Then
            If cmbFieldA.Text = "" Or cmbOperA.Text = "" Or txtContentA.Text = "" Then
                MsgBox("查询条件不完整，请补充！", vbOKOnly, "提示信息")
                Exit Sub
            End If
        End If

        '若第一个关系选择不是空，则第二组选项不能为空
        If cmbRelationA.Text <> "" Then
            If cmbFieldB.Text = "" Or cmbOperB.Text = "" Or txtContentB.Text = "" Then
                MsgBox("查询条件不完整，请补充！", vbOKOnly, "提示信息")
                Exit Sub
            End If
        End If

        '若关系第二个关系选项不是空，则第三组选项不能为空
        If cmbRelationB.Text <> "" Then
            If cmbFieldC.Text = "" Or cmbOperC.Text = "" Or txtContentC.Text = "" Then
                MsgBox("查询条件不完整，请补充！", vbOKOnly, "提示信息")
                Exit Sub
            End If
        End If

        '按一般的查询操作进行
        Dim engroup As New Entity.GroupQueryEntity     '实例化实体

        engroup.cmbFieldA = GetEnglish(cmbFieldA.Text)     '将参数传入实体
        engroup.cmbFieldB = GetEnglish(cmbFieldB.Text)
        engroup.cmbFieldC = GetEnglish(cmbFieldC.Text)
        engroup.cmbOperA = cmbOperA.Text
        engroup.cmbOperB = cmbOperB.Text
        engroup.cmbOperC = cmbOperC.Text
        engroup.cmbRelationA = GetEnglish(cmbRelationA.Text)
        engroup.cmbRelationB = GetEnglish(cmbRelationB.Text)
        engroup.txtContextA = txtContentA.Text
        engroup.txtContextB = txtContentB.Text
        engroup.txtContextC = txtContentC.Text

        '将得到的表名也传给实体
        engroup.GetTable = GetTable()

        '调用子类的方法，继续执行余下的查询的操作
        QueryClick(engroup)

    End Sub


    ''' <summary>  
    ''' 模板方法：定义虚函数GetEnglish，查询字段转化为数据库字段（英文）  
    ''' </summary>  
    ''' <param name="cmbField "></param>  
    ''' <returns></returns>  
    ''' <remarks></remarks>  

    Public Overridable Function GetEnglish(cmbField As String) As String
        Return ""
    End Function

    '''<summary>
    ''' 定义虚函数GetTable，获取不同数据库的表名
    ''' </summary>
    ''' <returns></returns>
    ''' <remarks></remarks>

    Public Overridable Function GetTable() As String
        Return ""
    End Function

    ''' <summary>  
    ''' 查询时非公共的部分  
    ''' </summary>  
    ''' <remarks></remarks> 

    Protected Overridable Sub QueryClick(ByVal engroup As Entity.GroupQueryEntity)

    End Sub</span></span></span>

      子窗体需要重写父窗体的方法和自己的一些基本信息。

Private Sub FrmOperatorWorklog_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Me.Text = "操作员工作记录"
        '填写基本信息
        cmbFieldA.Items.Add("教师")
        cmbFieldA.Items.Add("登陆日期")
        cmbFieldA.Items.Add("登陆时间")
        cmbFieldA.Items.Add("退出日期")
        cmbFieldA.Items.Add("退出时间")
        cmbFieldA.Items.Add("机器名")

        cmbFieldB.Items.Add("教师")
        cmbFieldB.Items.Add("登陆日期")
        cmbFieldB.Items.Add("登陆时间")
        cmbFieldB.Items.Add("退出日期")
        cmbFieldB.Items.Add("退出时间")
        cmbFieldB.Items.Add("机器名")

        cmbFieldC.Items.Add("教师")
        cmbFieldC.Items.Add("登陆日期")
        cmbFieldC.Items.Add("登陆时间")
        cmbFieldC.Items.Add("退出日期")
        cmbFieldC.Items.Add("退出时间")
        cmbFieldC.Items.Add("机器名")
    End Sub

    '重写字段名到数据库字段名的转换
    Public Overrides Function GetEnglish(cmbField As String) As String
        Select Case cmbField
            Case "教师"
                GetEnglish = "userID"
            Case "登陆日期"
                GetEnglish = "loginDate"
            Case "登陆时间"
                GetEnglish = "loginTime"
            Case "退出日期"
                GetEnglish = "logoutDate"
            Case "退出时间"
                GetEnglish = "logoutTime"
            Case "机器号"
                GetEnglish = "computer"
            Case "与"
                GetEnglish = "and"
            Case "或"
                GetEnglish = "or"
            Case Else
                GetEnglish = ""
        End Select
    End Function

    '重写得到数据库表名
    Public Overrides Function GetTable() As String
        Return "Worklog_Info"
    End Function

    '继父类中的btnQuery_Click()事件
    Protected Overrides Sub QueryClick(ByVal engroup As Entity.GroupQueryEntity)


        '返回实体
        Dim myList As IList(Of Entity.WorklogEntity)
        Dim Boperator As New BLL.GroupQueryBLL

        myList = Boperator.OperatorWorklog(engroup)

        If myList.Count = 0 Then
            MsgBox("没有记录！", vbOKOnly, "提示信息")
        Else
            myDataGrid.DataSource = myList

            myDataGrid.Columns.Remove("logoutDate")
            myDataGrid.Columns.Remove("logoutTime")
            myDataGrid.Columns.Remove("status")

            myDataGrid.Columns(0).HeaderText = "系列号"
            myDataGrid.Columns(1).HeaderText = "用户名"
            myDataGrid.Columns(2).HeaderText = "用户级别"
            myDataGrid.Columns(3).HeaderText = "登陆日期"
            myDataGrid.Columns(4).HeaderText = "登陆时间"
            myDataGrid.Columns(5).HeaderText = "机器名"

        End If

    End Sub

     B层比较简单，就是一个传递的过程。

<span style="font-size:18px;"><span style="font-size:18px;">Public Function OperatorWorklog(ByVal engroup As Entity.GroupQueryEntity) As IList(Of Entity.WorklogEntity)
        Dim myList As IList(Of Entity.WorklogEntity)
        Dim sqlFactory As New DataAccess.SqlFactory
        Dim iGroupQuery As IDAL.IGroupQuery

        iGroupQuery = sqlFactory.CreateGroupQuery

        myList = iGroupQuery.OperatorWorklog(engroup)

        Return myList
    End Function</span></span>

     D层只需调用一个存储过程，其他的都一样。

<span style="font-size:18px;"><span style="font-size:18px;">'下面是相同部分
        Dim dataTable As New DataTable
        Dim strText As String = "PROC_GroupQuery"
        Dim sqlParams As SqlParameter() = {New SqlParameter("@cmbFieldA", engroup.cmbFieldA),
                                          New SqlParameter("@cmbFieldB", engroup.cmbFieldB),
                                           New SqlParameter("@cmbFieldC", engroup.cmbFieldC),
                                           New SqlParameter("@cmbOperA", engroup.cmbOperA),
                                           New SqlParameter("@cmbOperB", engroup.cmbOperB),
                                           New SqlParameter("@cmbOperC", engroup.cmbOperC),
                                           New SqlParameter("@txtContextA", engroup.txtContextA),
                                           New SqlParameter("@txtContextB", engroup.txtContextB),
                                           New SqlParameter("@txtContextC", engroup.txtContextC),
                                           New SqlParameter("@cmbRelationA", engroup.cmbRelationA),
                                           New SqlParameter("@cmbRelationB", engroup.cmbRelationB),
                                           New SqlParameter("@GetTable", engroup.GetTable)}

        Dim helper As New SqlHelper

        dataTable = helper.ExecuteQuery(strText, CommandType.StoredProcedure, sqlParams)

        '下面是不同的部分
        Dim myList As IList(Of Entity.WorklogEntity)

        myList = EntitySetGeneric.ConvertToList(Of Entity.WorklogEntity)(dataTable)
        Return myList</span></span>

     公用的实体类，这个实体是以组合窗体上的几个控件为依据，负责传递控件中的数据：

<span style="font-size:18px;"><span style="font-size:18px;">Public Class GroupQueryEntity
    Private cmbField1 As String
    Private cmbField2 As String
    Private cmbField3 As String
    Private cmbOper1 As String
    Private cmbOper2 As String
    Private cmbOper3 As String
    Private txtContext1 As String
    Private txtContext2 As String
    Private txtContext3 As String
    Private cmbRelation1 As String
    Private cmbRelation2 As String

    Private EGetTable As String

    Public Property cmbFieldA() As String
        Get
            Return cmbField1
        End Get
        Set(value As String)
            cmbField1 = value
        End Set
    End Property

    Public Property cmbFieldB() As String
        Get
            Return cmbField2
        End Get
        Set(value As String)
            cmbField2 = value
        End Set
    End Property

    Public Property cmbFieldC() As String
        Get
            Return cmbField3
        End Get
        Set(value As String)
            cmbField3 = value
        End Set
    End Property

    Public Property cmbOperA() As String
        Get
            Return cmbOper1
        End Get
        Set(value As String)
            cmbOper1 = value
        End Set
    End Property

    Public Property cmbOperB() As String
        Get
            Return cmbOper2
        End Get
        Set(value As String)
            cmbOper2 = value
        End Set
    End Property

    Public Property cmbOperC() As String
        Get
            Return cmbOper3
        End Get
        Set(value As String)
            cmbOper3 = value
        End Set
    End Property

    Public Property txtContextA() As String
        Get
            Return txtContext1
        End Get
        Set(value As String)
            txtContext1 = value
        End Set
    End Property

    Public Property txtContextB() As String
        Get
            Return txtContext2
        End Get
        Set(value As String)
            txtContext2 = value
        End Set
    End Property

    Public Property txtContextC() As String
        Get
            Return txtContext3
        End Get
        Set(value As String)
            txtContext3 = value
        End Set
    End Property

    Public Property cmbRelationA() As String
        Get
            Return cmbRelation1
        End Get
        Set(value As String)
            cmbRelation1 = value
        End Set
    End Property

    Public Property cmbRelationB() As String
        Get
            Return cmbRelation2
        End Get
        Set(value As String)
            cmbRelation2 = value
        End Set
    End Property

    Public Property GetTable As String
        Get
            Return EGetTable
        End Get
        Set(value As String)
            EGetTable = value
        End Set
    End Property

End Class
</span></span>

     重点说一下D层调用的存储过程。一定要注意存储过程中SQL语句的空格。在select * from 后面有一空格，where前后都要有空格。

<span style="font-size:18px;"><span style="font-size:18px;">ALTER PROCEDURE [dbo].[PROC_GroupQuery]
	@cmbFieldA varchar(50),
	@cmbFieldB varchar(50),
	@cmbFieldC varchar(50),
	@cmbOperA varchar(50),
	@cmbOperB varchar(50),
	@cmbOperC varchar(50),
	@txtContextA varchar(50),
	@txtContextB varchar(50),
	@txtContextC varchar(50),
	@cmbRelationA varchar(50),
	@cmbRelationB varchar(50),
	@GetTable varchar(50)
AS
	--定义一个临时变量
	declare @temp as varchar(500)
BEGIN
	set  @temp ='select * from '+@gettable+' where '+@cmbFieldA+@cmbOperA+CHAR(39)+@txtContextA+CHAR(39)
	if @cmbRelationA !=''
	BEGIN
		set @temp =@temp+CHAR(32)+@cmbRelationA +CHAR(32)+@cmbFieldB+@cmbOperB+CHAR(39)+@txtContextB+CHAR(39)
	if @cmbRelationB !=''
		set @temp =@temp+CHAR(32)+@cmbRelationB+CHAR(32)+@cmbFieldC+@cmbOperC+CHAR(39)+@txtContextC+CHAR(39)
	END

	--返回查询到的表
	exec (@temp)
    
   END</span></span>

     提醒：存储过程要有返回值！上述代码返回的是查询到的表。另外，select  变量名 （例：select @temp）返回的是查询语句。

     简单提一下前两种使用模板的窗体。

     第一种：将查询卡号是否存在和导出Excel表放在父窗体中。

     第二种：将导出Excel表放在父窗体中，建立一个公用的实体，存放起始和终止日期。

    只要会做组合查询了，另外两种就是小case。

     最后，说一句使用模板方法有遗憾事，本想着组合查询这么多窗体只需要B层和D层中的一个类，做得时候才发现不是那么一回事，有几个子窗体就需要几个B层和D层中的类。不知道有没有人能解决这个问题，这样用让我感觉还是有点麻烦！（注：返回的是泛型集合才行！）