vb.net机房收费系统重构——反射加七层登陆
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 ClassUserEntity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 cmdType As CommandType, 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。