机房重构---七层登录

前言：

从C#版三层登录开始，到VB.NET版三层登录，再到VB.NET版七层登录，一步步走向机房重构的正规化，其中也经历了很多的波折。刚开始不知道从哪里下手，不断的查询各种资料，慢慢了解，终于有了进展，还是蛮开心的。我的建议是如果实在不知道如何下手，没有思路，别停滞不前，不防先从简单的代码敲起，不断敲，不断查询学习，敲着敲着就会慢慢培养出感觉来。

七层构成：

七层和三层相比，多了一个外观层（Facade）、一个接口层（IDAL）、还多了一个工厂层（Factory）。关于sqlHelper可以单独放到一个包中（如下图），也可以和DAL层放到一起。

七层登录：

U层：

接受用户传来的数据，传给外观层，再由外观层传给B层进行相应的判断。

'**********************************************

'文件名：frmLogin

'作者：袁甜梦

'小组：袁甜梦

'说明:

'创建日期：2016/2/29 19:40:40

'版本号：V1.0.0.0

'**********************************************
Imports Entity
Imports Facade
Public Class frmLogin
Private Sub btnLogin_Click(sender As Object, e As EventArgs) Handles btnLogin.Click
'进行输入框的判断
If txtUserName.Text = "" Then
MsgBox("请输入用户名!", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
txtUserName.Focus()
Exit Sub
End If
If IsNumeric(txtUserName.Text) = False Then
MsgBox("用户名请输入数字！", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
txtUserName.Text = ""
Exit Sub
End If
If txtPassword.Text = "" Then
MsgBox("请输入密码！", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
txtPassword.Focus()
Exit Sub
End If
Try
'实例化所需的各层的类
Dim Facade As New Facade.LoginFacade
Dim UserInfo As New Entity.LoginUserInfo
UserInfo.UserName = txtUserName.Text.Trim
UserInfo.Password = txtPassword.Text
Dim strResult As Boolean
'将U层的信息传入外观层，然后再有外观层传入B层进行判断
strResult = Facade.CheckUser(UserInfo)
If strResult = False Then   '判断用户是否存在
MsgBox("该用户不存在，请重新输入！", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
txtUserName.Text = ""
txtPassword.Text = ""
txtUserName.Select()
txtUserName.Focus()
End If
Dim table As DataTable
table = Facade.CheckPwd(UserInfo)
If Trim(txtPassword.Text) = Trim(table.Rows(0).Item(2)) Then
MsgBox("登录成功！")
Me.Hide()
txtUserName.Text = ""
txtPassword.Text = ""
End If
Catch ex As Exception
MsgBox("用户不存在或密码不正确！")
txtPassword.Text = ""
txtUserName.Text = ""
txtUserName.Select()
txtUserName.Focus()
End Try
End Sub

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

End Class

Facade层：

解耦U层和B层。

'**********************************************

'文件名：LoginFacade

'作者：袁甜梦

'小组：袁甜梦

'说明:

'创建日期：2016/2/29 19:11:40

'版本号：V1.0.0.0

'**********************************************
Imports BLL
Imports Entity
Public Class LoginFacade
'判断用户是否存在
Public Function CheckUser(ByVal UserInfo As Entity.LoginUserInfo) As Boolean
Dim IsUserExists As New BLL.LoginBLL
Dim flag As Boolean
flag = IsUserExists.Checkuser(UserInfo)
If flag = True Then
Return True
Else
Return False
End If
End Function
'判断密码是否正确
Public Function CheckPwd(ByVal UserInfo As Entity.LoginUserInfo) As DataTable
Dim IsPwdExists As New BLL.LoginBLL
Dim table As DataTable
table = IsPwdExists.Checkpwd(UserInfo)
Return table
End Function

End Class

BLL层：

'**********************************************

'文件名：LoginBLL

'作者：袁甜梦

'小组：袁甜梦

'说明:

'创建日期：2016/2/29 17:30:53

'版本号：V1.0.0.0

'**********************************************
Imports IDAL
Imports Entity
Imports Factory
Public Class LoginBLL
'检查用户是否存在
Public Function Checkuser(ByVal UserInfo As Entity.LoginUserInfo) As Boolean
Dim Factory As New Factory.LoginFactory
Dim IUser As IDAL.LoginIUserInfo
'调用创建用户的工厂方法
IUser = Factory.CreateIUser() '调用工厂的CreateIUser方法创建IUser接口实例
Dim table As New DataTable
Dim flag As Boolean
table = IUser.selectUser(UserInfo)
If table.Rows.Count = 0 Then
flag = False
Else
flag = True
End If
Return flag
End Function
'检查用户密码是否正确
Public Function Checkpwd(ByVal UserInfo As Entity.LoginUserInfo) As DataTable
Dim Factory As New Factory.LoginFactory
Dim IUser As IDAL.LoginIUserInfo
Dim table As DataTable

IUser = Factory.CreateIUser
table = IUser.selectUser(UserInfo)
Return table
End Function
End Class

Factory层：

'**********************************************

'文件名：LoginFactory

'作者：袁甜梦

'小组：袁甜梦

'说明:

'创建日期：2016/2/29 17:36:26

'版本号：V1.0.0.0

'**********************************************
Imports System.Reflection '反射
Imports System.Configuration '配置文件
Imports System.Data
Imports IDAL
Public Class LoginFactory
Private Shared ReadOnly AssemblyName As String = "DAL" '数据程序集名称，命名空间DAL
Dim strDB As String = System.Configuration.ConfigurationSettings.AppSettings("DB")
Public Function CreateIUser() As LoginIUserInfo
Dim classname As String = "DAL" + "." + strDB + "LoginDAL" '要实例化的D层的名称
'Dim classname As String = "DAL" + "." + "LoginDAL"
Dim IUser As LoginIUserInfo
'CType函数将返回表达式显示的转换为指定的数据类型、对象、结构、类或接口后的结果
IUser = CType(Assembly.Load(AssemblyName).CreateInstance(classname), LoginIUserInfo) '返回LoginIUserInfo
Return IUser
End Function

End Class

IDAL层：

Imports Entity
Public Interface LoginIUserInfo
'判断用户是否存在
Function selectUser(ByVal UserInfo As Entity.LoginUserInfo) As DataTable
End Interface

DAL层：

'**********************************************

'文件名：LoginDAL

'作者：袁甜梦

'小组：袁甜梦

'说明:

'创建日期：2016/3/1 15:24:24

'版本号：V1.0.0.0

'**********************************************
Imports Entity
Imports IDAL
Imports SqlHelper
Imports System.Data.SqlClient

Public Class LoginDAL : Implements IDAL.LoginIUserInfo
'实现接口中的方法
Private sqlHelper As New SqlHelper.sqlhelper
'判断用户是否存在
Public Function selectUser(UserInfo As LoginUserInfo) As DataTable Implements LoginIUserInfo.selectUser
Dim sql As String '中间变量，用于存储从数据库中查到的信息
Dim table As DataTable
'声明并实例化参数数组
Dim sqlParams As SqlParameter() = {New SqlParameter("@UserName", UserInfo.UserName),
New SqlParameter("@Password", UserInfo.Password)}
sql = "select * from Users where UserName=@UserName and Password=@Password"
'调用sqlHelper类中的ExecSelect方法来执行查询并获取返回值
table = sqlHelper.ExecSelect(sql, CommandType.Text, sqlParams)
Return table

End Function

End Class

sqlHelper层：

'**********************************************

'文件名：sqlhelper

'作者：袁甜梦

'小组：袁甜梦

'说明:

'创建日期：2016/2/29 16:07:28

'版本号：V1.0.0.0

'**********************************************
Imports System.Data
Imports System.Data.SqlClient
Imports System.Configuration
Public Class sqlhelper
'数据库连接
Dim strConnction As String = "Server=YUAN; Database=StudentInfo;User ID=sa;Password=930201"
Dim conn As New SqlConnection(strConnction)
Dim cmd As New SqlCommand

Public Function ExecSelect(ByVal cmdText As String, ByVal cmdType As CommandType, ByVal paras As SqlParameter()) As DataTable
Dim sqlAdapter As SqlDataAdapter '定义数据适配器
Dim dt As New DataTable
Dim ds As New DataSet
'给cmd赋值
cmd.CommandText = cmdText 'cmdText为所要执行的sql语句
cmd.CommandType = cmdType '命令执行的类型
cmd.Connection = conn
cmd.Parameters.AddRange(paras) '参数添加
sqlAdapter = New SqlDataAdapter(cmd) '实例化Adapter
Try
sqlAdapter.Fill(ds) '用adapter将dataset填充
dt = ds.Tables(0) 'datatable为dataSet的第一个表
cmd.Parameters.Clear() '清除参数
Catch ex As Exception
MsgBox("数据库操作")
Finally
Call CloseCmd(cmd) '销毁cmd命令
End Try
Return dt
End Function
Public Sub CloseCmd(ByVal cmd As SqlCommand)
If Not IsNothing(cmd) Then 'cmd命令存在
cmd.Dispose() '销毁
cmd = Nothing
End If
End Sub
End Class

Entity层：

'**********************************************

'文件名：LoginEntity

'作者：袁甜梦

'小组：袁甜梦

'说明:

'创建日期：2016/2/29 15:41:43

'版本号：V1.0.0.0

'**********************************************
Public Class LoginUserInfo
'设置用户名属性
Private _username As String
Public Property UserName As String
Get
Return _username
End Get
Set(value As String)
_username = value
End Set
End Property
Private _password As String
'设置密码的属性
Public Property Password As String
Get
Return _password
End Get
Set(value As String)
_password = value
End Set
End Property

End Class

配置文件：

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
</startup>
<appSettings>
<add key="connstring" value="Server=YUAN;Database=StudentInfo;User ID=sa;Password=930201"/>
</appSettings >
</configuration>

运行结果：

注意：

在运行之前需要更改DAL的编译路径，否则会出现错误。
错误提示：





路径更改方法：