vb.net机房收费系统重构——反射加七层登陆

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前端之家收集整理的这篇文章主要介绍了vb.net机房收费系统重构——反射加七层登陆，前端之家小编觉得挺不错的，现在分享给大家，也给大家做个参考。

重构机房收费系统时，刚开始用三层敲写，完成后觉得很多东西没用到，比如外观模式，抽象工厂加反射等，因此又推翻了重新敲写七层，各种参数的传递刚开始确实有些不明白，经过一段时间的查资料和摸索之后有了些感觉。

七层其实就是在远在三层框架的基础上添加了接口（IDAL），工厂（Factory)，外观（Facade)，以及贯穿始终的实体层(Entity)。由于已经有不少大神做的七层包图，在此也就不再展示。

首先：实体层（Entity）

实体对象实际上是对应着数据库里的每张表的,我们把表里的字段封装在1个实体对象里 当你想用哪个字段 你就就通过该实体对象的get() set() 把那个字段提取出来 这比你临时创建1个变量要灵活的多 而且便于程序的维护和扩展.在实际的3层结构开发中,专门有个实体层,他的作用就是便于层和层之间的数据传递。

登录中，我用UserEntity对应数据库中的T_User表，也就是用户基本信息表。

'用户实体类，对应T_User表

Public Class UserEntity
    Private _id As String
    Private _password As String
    Private _username As String
    Private _level As String
    Private _Head As String

    Public Property ID() As String
        Get
            Return _id
        End Get
        Set(value As String)
            _id = value
        End Set
    End Property

    Public Property Password() As String
        Get
            Return _password
        End Get
        Set(value As String)
            _password = value
        End Set
    End Property

    Public Property UserName() As String
        Get
            Return _username
        End Get
        Set(value As String)
            _username = value
        End Set
    End Property

    Public Property Level() As String
        Get
            Return _level
        End Get
        Set(value As String)
            _level = value
        End Set
    End Property

    Public Property Head() As String
        Get
            Return _Head
        End Get
        Set(value As String)
            _Head = value
        End Set
    End Property
End Class
UserEntity中的每个字段对应了T_User表中的每个字段。
然后自顶向下，UI层

对应代码如下

<span style="font-size:18px;">Public Class frmLoginUI

    Private Sub btnLogin_Click(sender As Object,e As EventArgs) Handles btnLogin.Click

        '把用户名和密码放到一个实体中
        Dim user As New Entity.UserEntity
        user.ID = txtUsername.Text.Trim()
        user.Password = txtPassword.Text


        Dim LoginUI As New Facade.LoginFac
        Dim strResult As String
        strResult = LoginUI.login(user)


        '用户名和密码验证的几种情况
        Select Case strResult

            Case "此用户不存在"
                MsgBox("此用户不存在，请重新输入用户名!")
                txtUsername.Focus()
                txtUsername.SelectAll()

            Case "密码错误"
                MsgBox("密码错误，请重新输入!")
                txtPassword.Focus()
                txtPassword.SelectAll()

            Case "登陆成功"

                frmMain.Show()
                Me.Close()

        End Select


    End Sub

    Private Sub btnCancel_Click(sender As Object,e As EventArgs) Handles btnCancel.Click

        End

    End Sub
End Class</span>

判断用户名的密码时此处是应用了外观模式，通过在U层和B层中添加一个外观层Facade 
<span style="font-size:18px;">Public Class LoginFac
    Public Function login(ByVal user As Entity.UserEntity) As String
        Dim ConfirmUserBLL As New BLL.ConfirmUser

        '调用B层方法验证用户名和密码是否存在
        If Not ConfirmUserBLL.IsExits(user) Then
            Return "此用户不存在"
        Else
            If Not ConfirmUserBLL.ConfirmPWD(user) Then
                Return "密码错误"
            Else
                Return "登陆成功"
            End If
        End If
    End Function
End Class</span>

其实本人认为外观层在这里并不是非加不可，也可直接调用B层 
<span style="font-size:18px;">Imports IDAL
Public Class ConfirmUser
    '验证用户名是否正确
    Public Function IsExits(ByVal user As Entity.UserEntity) As Boolean
        Dim Iuser As IDAL.IUser
        Dim factory As New Factory.DBFactory
        Dim Iworklog As IDAL.IWorklog
        Iuser = factory.CreateUserDAO()
        Iworklog = factory.CreateWorklog()
        Dim table As New DataTable

        table = Iuser.SelectUser(user)

        If table.Rows.Count = 0 Then

            Return False

        Else

            Return True

        End If

    End Function

    '验证密码是否正确
    Public Function ConfirmPWD(ByVal password As Entity.UserEntity) As Boolean
        Dim Iuser As IDAL.IUser
        Dim factory As New Factory.DBFactory

        Iuser = factory.CreateUserDAO
        Dim table As New DataTable
        table = Iuser.SelectUser(password)

        If table.Rows.Count = 0 Then

            Throw New Exception("输入的密码不正确")

            Return False
        Else

            Return True

        End If

    End Function
End Class
</span>

在链接数据库时采用抽用抽象工厂加反射Factory 
<span style="font-size:18px;">'抽象工厂，负责数据库的选择和创建接口

Imports System.Reflection
Imports System.Configuration
Imports IDAL
Public Class DBFactory
    Dim strDB As String = System.Configuration.ConfigurationSettings.AppSettings("DB")

    Private Shared ReadOnly assemblyName = "DAL"

    Public Function CreateUserDAO() As IDAL.IUser

        Dim className As String = assemblyName + "." + "UserDAL"
        Return CType(Assembly.Load(assemblyName).CreateInstance(className),IDAL.IUser)   '返回IUser  


    End Function

End Class
</span>

接口IDAL 
<span style="font-size:18px;">mports System.Data.DataTable
Public Interface IUser
    Function SelectUser(ByVal User As Entity.UserEntity) As System.Data.DataTable
End Interfac
</span>

D层用来将接口实例化

<span style="font-size:18px;">Imports System.Data.sqlClient

Public Class UserDAL : Implements IDAL.IUser

    Public Function SelectUser(ByVal User As Entity.UserEntity) As System.Data.DataTable Implements IDAL.IUser.SelectUser

        Dim sqlParams As sqlParameter() = {New sqlParameter("@UserID",User.ID),New sqlParameter("@Password",User.Password)}
        Dim strsql As String = "select * from T_User where UserID=@UserID"

        Dim helper As New sqlHelper '实例化sqlHelper

        'Dim cmdType As CommandType = New CommandType()
        'cmdType = CommandType.StoredProcedure '定义命令类型为存储过程

        Dim table As New DataTable
        table = helper.GetDataTable(strsql,CommandType.Text,sqlParams)
        Return table

    End Function




End Class
</span>
我将sqlHelper放到了D层

开始不明白什么是sqlHelper，后来查阅了一些资料，加上编写应用实例，现在明白些。

sqlHelper用于简化你重复的去写那些数据库连接（sqlConnection）,sqlCommand,sqlDataReader等等。sqlHelper 封装过后通常是只需要给方法传入一些参数如数据库连接字符串，sql参数等，就可以访问数据库了，很方便。

<span style="font-size:18px;">Imports System.Data
Imports System.Data.sqlClient
Imports System.Configuration
Imports System.Reflection
Public Class sqlHelper
    '利用配置文件寻找“连接字符串”，建立cmd文件
    Private ReadOnly constr As String = System.Configuration.ConfigurationSettings.AppSettings("strConn")
    Dim conn As New sqlConnection(constr)
    Dim cmd As New sqlCommand

    ''' <summary>
    ''' 带参数，返回结果是表
    ''' </summary>
    ''' <param name="cmdTxt"></param>
    ''' <param name="cmdType"></param>
    ''' <param name="sqlparams"></param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Public Function GetDataTable(ByVal cmdTxt As String,ByVal cmdType As CommandType,ByVal sqlparams As sqlParameter()) As DataTable

        cmd = conn.CreateCommand()

        '利用传进的参数填充cmd对象
        cmd.CommandText = cmdTxt
        cmd.CommandType = cmdType
        cmd.Parameters.AddRange(sqlparams)


        Dim sqlAdapter As New sqlDataAdapter(cmd) '定义数据适配器变量，并实例化，将cmd绑定在adaptor上面
        Dim dssql As New DataSet  '定义数据缓存变量

        Try
            conn.Open()
            sqlAdapter.Fill(dssql) '用adapter将dataset填充
            Return dssql.Tables(0)
        Catch ex As Exception
            Return Nothing
            MsgBox(ex.Message,"数据库操作")
        Finally
            Call closeConn(conn)
        End Try

    End Function

    ''' <summary>
    ''' 不带参数，返回结果是表
    ''' </summary>
    ''' <param name="cmdTxt"></param>
    ''' <param name="cmdType"></param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Public Function GetDataTable(ByVal cmdTxt As String,ByVal cmdType As CommandType) As DataTable
        cmd = conn.CreateCommand()

        '利用传进的参数填充cmd对象
        cmd.CommandText = cmdTxt
        cmd.CommandType = cmdType


        'Dim dtsql As New DataTable '定义数据表格
        Dim sqlAdapter As New sqlDataAdapter(cmd) '定义数据适配器变量，并实例化，将cmd绑定在adaptor上面
        Dim dssql As New DataSet  '定义数据缓存变量

        Try
            conn.Open()
            sqlAdapter.Fill(dssql)      '用adapter将dataset填充  
            Return dssql.Tables(0)
        Catch ex As Exception
            MsgBox(ex.Message,"数据库操作")
        Finally
            Call closeConn(conn)
        End Try
        Return dssql.Tables(0)

    End Function

    ''' <summary>
    ''' 带参数，返回结果是值
    ''' </summary>
    ''' <param name="cmdTxt"></param>
    ''' <param name="cmdType"></param>
    ''' <param name="sqlparams"></param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Public Function ExecuteNonQuery(ByVal cmdTxt As String,ByVal sqlparams As sqlParameter()) As Integer
        cmd = conn.CreateCommand()
        Dim sqlAdapter As New sqlDataAdapter(cmd)
        Dim dssql As New DataSet
        '利用传进的参数填充cmd对象
        cmd.CommandText = cmdTxt
        cmd.CommandType = cmdType
        cmd.Parameters.AddRange(sqlparams)


        Try
            conn.Open()
            sqlAdapter.Fill(dssql)
            Return dssql.Tables.Count
        Catch ex As Exception
            Return Nothing
            MsgBox(ex.Message,"数据库操作")
        Finally
            Call closeConn(conn)
        End Try


    End Function


    ''' <summary>
    ''' 不带参数，返回结果是值
    ''' </summary>
    ''' <param name="cmdTxt"></param>
    ''' <param name="cmdType"></param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Public Function ExecuteNonQuery(ByVal cmdTxt As String,ByVal cmdType As CommandType) As Integer
        cmd = conn.CreateCommand()

        Dim dssql As New DataSet
        '利用传进的参数填充cmd对象
        cmd.CommandText = cmdTxt
        cmd.CommandType = cmdType

        Dim sqlAdapter As New sqlDataAdapter(cmd)
        
        Try
            conn.Open()
            'int = cmd.ExecuteNonQuery()
            sqlAdapter.Fill(dssql)

        Catch ex As Exception
            MsgBox(ex.Message,"数据库操作")
        Finally
            Call closeConn(conn)
        End Try
        'Return int
        Return dssql.Tables.Count
    End Function

    '关闭数据库连接
    Public Shared Sub closeConn(ByVal conn As sqlConnection)
        If conn.State = ConnectionState.Open Then
            conn.Close()
        End If
    End Sub
End Class</span>
sqlHelper支持多种数据库包括MysqL、sqlServer、Oracle、Access数据库，如果数据库是sqlServer，那么你可以使用sqlServerHelper类，如果是MysqL，可以使用MysqLHelper，如果是Access，可以使用AccessHelper。如果是Oracle则可以使用OracleHelper类。 原文链接：https://www.f2er.com/vb/257509.html

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