机房重构——组合查询

    在重构的过程中发现有好多窗体是很相似的，设计模式这时候就派上用场了，模板方法可以很好的实现功能同时也减少代码量。

    模板方法模式：定义一个操作中的算法的骨架，而将一些步骤延迟到子类中模板方法使得子类可以不改变一个算法结构几个重定义该算法的某些特定步骤。

    结构图：

    

   实践：

 

   部分代码：

    U层：

Public Class FrmGropQuery

    Protected EGroup As New Entity.GroupQueryEntity  '实例化一个新的实体对象

    '窗体加载

    Private Sub FrmGropQuery_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        '窗体加载时，给字段、操作符、组合关系赋值
        '加载组合关系
        ComRelation1.Items.Add("与")
        ComRelation1.Items.Add("或")

        ComRelation2.Items.Add("与")
        ComRelation2.Items.Add("或")

        '给操作符赋值
        ComOperation1.Items.Add(">")
        ComOperation1.Items.Add("<")
        ComOperation1.Items.Add("=")
        ComOperation1.Items.Add("<>")

        ComOperation2.Items.Add(">")
        ComOperation2.Items.Add("<")
        ComOperation2.Items.Add("=")
        ComOperation2.Items.Add("<>")

        ComOperation3.Items.Add(">")
        ComOperation3.Items.Add("<")
        ComOperation3.Items.Add("=")
        ComOperation3.Items.Add("<>")

        '窗体加载后，后两行文本框不能用
        ComFields2.Enabled = False
        ComOperation2.Enabled = False
        txtContext2.Enabled = False

        ComFields3.Enabled = False
        ComOperation3.Enabled = False
        txtContext3.Enabled = False
    End Sub

    Private Sub BtnQuery_Click(sender As Object, e As EventArgs) Handles BtnQuery.Click
        '先将DataGridview中清空
        DataGridView1.DataSource = Nothing

        '判断文本框、组合框是否为空
        '第一个组合关系为空时，第一行的内容均不能为空
        If ComRelation1.Text = "" Then
            If ComFields1.Text = "" Or ComOperation1.Text = "" Or txtContext1.Text = "" Then
                MsgBox("第一行查询条件不能为空，请完善", , "提示")
                Exit Sub
            End If
        End If

        '第一个组合关系文本框不为空，则判断前两行不能为空
        If ComRelation1.Text <> "" Then
            If ComFields1.Text = "" Or ComOperation1.Text = "" Or txtContext1.Text = "" Or ComFields2.Text = "" Or ComOperation2.Text = "" Or txtContext2.Text = "" Then
                MsgBox("所输入的查询条件不能为空，请完善", , "提示")
                Exit Sub
            End If
        End If

        '第二个组合关系文本框不为空，判断所有的不为空
        If ComRelation2.Text <> "" Then
            If ComFields1.Text = "" Or ComOperation1.Text = "" Or txtContext1.Text = "" Or ComFields2.Text = "" Or ComOperation2.Text = "" Or txtContext2.Text = "" Or ComFields3.Text = "" Or ComOperation3.Text = "" Or txtContext3.Text = "" Then
                MsgBox("所输入的查询条件不能为空，请完善", , "提示")
                Exit Sub
            End If
        End If

        '给实体赋值（在实体层新建一个实体类）
        EGroup.Fields1 = GetDBName(ComFields1.Text.Trim())
        EGroup.Fields2 = GetDBName(ComFields2.Text.Trim())
        EGroup.Fields3 = GetDBName(ComFields3.Text.Trim())

        EGroup.Operation1 = ComOperation1.Text.Trim()
        EGroup.Operation2 = ComOperation2.Text.Trim()
        EGroup.Operation3 = ComOperation3.Text.Trim()

        EGroup.Context1 = txtContext1.Text.Trim()
        EGroup.Context2 = txtContext2.Text.Trim()
        EGroup.Context3 = txtContext3.Text.Trim()

        EGroup.Relation1 = GetDBName(ComRelation1.Text.Trim())
        EGroup.Relation2 = GetDBName(ComRelation2.Text.Trim())
        EGroup.GetList = GetList()

        Dim faca As New Facade.GroupQueryFacade
        Dim dt As New DataTable
        dt = faca.Query(EGroup)

        If (dt.Rows.Count = 0) Then
            MsgBox("没有符合条件的记录", , "提示")
            Exit Sub
        Else
            Call Dview()

        End If
    End Sub

    ' 定义虚函数GetDBName,获取不同数据库的字段名      
    Protected Overridable Function GetDBName(ByVal control As String) As String
        Return ""
    End Function
    ' 定义虚函数GetList,获取不同数据库的表名      
    Protected Overridable Function GetList() As String
        Return ""
    End Function
    '定义虚函数Dview,将数据显示到控件中  
    Protected Overridable Sub Dview()
    End Sub
    '组合关系框是否有值会影响到下边行能否操作
    Private Sub ComRelation1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComRelation1.SelectedIndexChanged
        If ComRelation1.Text <> "" Then
            ComFields2.Enabled = True
            ComOperation2.Enabled = True
            txtContext2.Enabled = True
        End If
    End Sub

    Private Sub ComRelation2_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComRelation2.SelectedIndexChanged
        If ComRelation2.Text <> "" Then
            ComFields3.Enabled = True
            ComOperation3.Enabled = True
            txtContext3.Enabled = True
        End If
    End Sub

    Private Sub BtnOut_Click(sender As Object, e As EventArgs) Handles BtnOut.Click
        Call UI.Exportexcel.ExportExcel(DataGridView1)

    End Sub

    Private Sub Btnclear_Click(sender As Object, e As EventArgs) Handles Btnclear.Click
        ComFields1.Text = ""
        ComFields2.Text = ""
        ComFields3.Text = ""

        ComOperation1.Text = ""
        ComOperation2.Text = ""
        ComOperation3.Text = ""

        ComRelation1.Text = ""
        ComRelation2.Text = ""

        txtContext1.Clear()
        txtContext2.Clear()
        txtContext3.Clear()

        DataGridView1.DataSource = Nothing
    End Sub
End Class

   D层：

Imports System.Data.SqlClient
Imports Entity
Imports IDAL
Imports SQLHelper
Public Class SqlserverGroupQueryDAL : Implements IGroupQuery
    Private sqlhelper As New SQLHelper.sqlHelper
    Public Function Query(user As GroupQueryEntity) As DataTable Implements IGroupQuery.Query
        Dim sql As String
        '调用存储过程
        sql = "PROC_GroupQuery"

        '加入参数
        Dim paras As SqlParameter() = {New SqlParameter("@Fields1", user.Fields1),
                                      New SqlParameter("@Fields2", user.Fields2),
                                      New SqlParameter("@Fields3", user.Fields3),
                                      New SqlParameter("@Operation1", user.Operation1),
                                      New SqlParameter("@Operation2", user.Operation2),
                                      New SqlParameter("@Operation3", user.Operation3),
                                      New SqlParameter("@Context1", user.Context1),
                                      New SqlParameter("@Context2", user.Context2),
                                      New SqlParameter("@Context3", user.Context3),
                                      New SqlParameter("@Relation1", user.Relation1),
                                      New SqlParameter("@Relation2", user.Relation2),
                                      New SqlParameter("@GetList", user.GetList)}
        Dim dt As DataTable
        dt = sqlhelper.ExecSelect(sql, CommandType.StoredProcedure, paras)
        Return dt
    End Function
End Class

   B层

Public Class GroupQueryBLL
    Function Query(ByVal user As Entity.GroupQueryEntity) As DataTable
        Dim fty As New Factory.GroupQueryFactory
        Dim IGroup As IDAL.IGroupQuery
        Dim dt As DataTable

        IGroup = fty.CreateGroupQuery
        dt = IGroup.Query(user)
        Return dt
    End Function
End Class

   外观层：

Public Class GroupQueryFacade
    Function Query(ByVal user As Entity.GroupQueryEntity) As DataTable
        Dim GQBll As New BLL.GroupQueryBLL
        Dim table As DataTable
        table = GQBll.Query(user)
        Return table
    End Function
End Class

   存储过程：

CREATE PROCEDURE [dbo].[PROC_GroupQuery]
    --加入参数  
    @Fields1  varchar(10),  
    @Fields2  varchar(10),  
    @Fields3  varchar(10),  

    @Operation1  varchar(10),  
    @Operation2  varchar(10),  
    @Operation3  varchar(10), 
	 
    @Context1  varchar(20),  
    @Context2  varchar(20),  
    @Context3  varchar(20), 
	 
    @Relation1  varchar(10),  
    @Relation2  varchar(10),  
    @GetList  varchar(20)       --获取表的名称  
      
AS  
    declare @TempSql varchar(500)--临时存放sql语句   
BEGIN  
    SET @TempSql='SELECT * FROM '+ @GetList +' WHERE ' + @Fields1 + @Operation1 + char(39) + @Context1 + char(39)      
    if @Relation1 != ''         --第一个组合关系文本框不为空  
    BEGIN  
    SET @TempSql=@TempSql+@Relation1+CHAR(32)+ @Fields2 + @Operation2 +CHAR(39) + @Context2+CHAR(39)      
        if @Relation2 != ''             --第二个组合关系文本框不为空  
        BEGIN      
        SET @TempSql=@TempSql+@Relation2 + CHAR(32)+ @Fields3 + @Operation3 + CHAR(39)+@Context3+CHAR(39)      
        END  
   END  
EXECUTE(@TempSql)  
END  

  以操作员工作记录为例：

   U层代码

Imports System.Collections '引入哈希表
Public Class FrmOperatorWorkLog

    Private Sub FrmOperatorWorkLog_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Me.Text = "操作员工作记录"    '表名

        Dim haField As New Hashtable '定义处理字段名转换的hashtable

        '使用哈希表进行数据库字段进行转换
        Dim FieldName() As String
        Dim FieldValue() As String

        '数据库中的字段对应相应的中文
        FieldName = {"教师", "级别", "登录日期", "登录时间", "注销日期", "注销时间", "机器名", "状态"}
        FieldValue = {"userID", "[level]", "loginDate", "loginTime", "logoutDate", "logoutTime", "computer", "status"}

        '放到Field字段中
        ComFields1.Items.AddRange(FieldName)
        ComFields2.Items.AddRange(FieldName)
        ComFields3.Items.AddRange(FieldName)

        '中文为key,英文为value添加到hashtable
        For i As Integer = 0 To FieldName.Count - 1
            haField.Add(FieldName(i), FieldValue(i))
        Next
    End Sub

    '重写获得表名方法
    Protected Overrides Function GetList() As String
        Return "T_WorkLogInfo"
    End Function

    '重写转换成数据库字段方法
    Protected Overrides Function GetDBName(control As String) As String
        Select Case (control)
            Case "教师"
                Return "userID"
            Case "级别"
                Return "[level]"
            Case "登录日期"
                Return "loginDate"
            Case "登录时间"
                Return "loginTime"
            Case "注销日期"
                Return "logoutDate"
            Case "注销时间"
                Return "logoutTime"
            Case "机器名"
                Return "computer"
            Case "状态"
                Return "status"
            Case Else
                Return ""
        End Select
    End Function

    Protected Overrides Sub Dview()
        '每次数据查询清空表
        DataGridView1.DataSource = Nothing

        '表格控件绑定数据源字段
        '调用外观，进行传递参数
        Dim fac As New Facade.GroupQueryFacade
        Dim dt As New DataTable

        dt = fac.Query(EGroup)

        If dt.Rows.Count = 0 Then
            MsgBox("没有记录，请重新进行查询！", vbExclamation, "警告")
            DataGridView1.DataSource = Nothing
        Else
            DataGridView1.DataSource = dt
            DataGridView1.Columns(0).HeaderText = "教师"
            DataGridView1.Columns(1).HeaderText = "级别"
            DataGridView1.Columns(2).HeaderText = "登录日期"
            DataGridView1.Columns(3).HeaderText = "登录时间"
            DataGridView1.Columns(4).HeaderText = "注销日期"
            DataGridView1.Columns(5).HeaderText = "注销时间"
            DataGridView1.Columns(6).HeaderText = "机器名"
            DataGridView1.Columns(7).HeaderText = "状态"


            '删除最后一空白行
            DataGridView1.AllowUserToAddRows = False
        End If
    End Sub
End Class

   总结：用了模板方法感觉方便了好多，但这也只是功能的实现有一些地方需要进一步优化！