机房重构——七层登录

【前言】

七层登录可真是历经千辛万苦呀，不过现在已经实现了，心情还是开心的不要不要滴。

【正文】

Why？

七层其实就是在三层的基础上又加了四层，主要就是为了解耦，使各层之间的数据不是直接的连接，而是通过七层传递。

What？

UI层：接收和显示用户的需求，将参数传递给外观层。

Facade层：传递参数，将UI层与BLL层分离。其实就是用了一个外观模式，作用就是解除B层与U层之间的耦合

BLL层：主要业务的判断和处理。

Factory层：使用抽象工厂+反射+配置文件，让数据库可以随时更换。以及将DAL层的类转换成IDAL层的接口实现，从而BLL层可以通过IDAL层访问DAL层。

IDAL：数据访问层，解耦BLL层和DAL层。就是提供接口

DAL层：数据层，对数据的增删改查。

Entity：实体层，贯穿于各层之间，联系各层。就是存储数据的，方便在各个层之间传递数据，多数作为类中方法的参数

SqlHelper层：主要是DAL的封装和抽象。

How?

先来看一下七层的包图

接下来看一下七层登录的时序图

接下来看一下实现的代码

U层

Public Class frmLogin    Private Sub btnLogin_Click(sender As Object, e As EventArgs) Handles btnLogin.Click        '判断是否为空        If txtUserName.Text = "" Then            MsgBox("请输入用户名", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)            txtUserName.Focus()            Exit Sub '过程内 代码执行时 选择性的中途推出        End If        If txtPassWord.Text = "" Then            MsgBox("请输入密码", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)            Exit Sub        End If        If IsNumeric(txtPassWord.Text) = False Then            MsgBox("请输入数字", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)            Exit Sub        End If        Try            Dim Facade As New Facade.LoginFacade            Dim UserInfo As New Entity.LoginUserInfo            UserInfo.UserName = txtUserName.Text.Trim()            UserInfo.PassWord = txtPassWord.Text.Trim()            Dim strResult As Boolean            '将U层的用户信息传入外观层，然后通过外观层传入B层进行判断            strResult = Facade.CheckUser(UserInfo)            If strResult = False Then                MsgBox("用户名不存在", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)                txtUserName.Text = ""                txtPassWord.Text = ""                txtUserName.Select()                txtUserName.Focus()                Exit Sub            End If            Dim table As DataTable            table = Facade.CheckPWD(UserInfo)            If Trim(txtPassWord.Text) = Trim(table.Rows(0).Item(1)) Then                MsgBox("登录成功")                Me.Hide()                txtPassWord.Text = ""                txtUserName.Text = ""            End If        Catch ex As Exception            MsgBox("用户名或密码不正确")            txtPassWord.Text = ""            txtUserName.Text = ""            txtUserName.Select()            txtUserName.Focus()            Exit Sub        End Try    End Sub '一个过程的退出    Private Sub btnCancel_Click(sender As Object, e As EventArgs) Handles btnCancel.Click        End    End SubEnd Class

Facade层

Public Class LoginFacade    '检查用户名是否存在    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    '检查密码是否存在    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 FunctionEnd Class

BLL层

Public Class LoginBLL    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()        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    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 FunctionEnd Class

Factory层

Imports System.Reflection '添加对 反射 的引用Imports System.Configuration '添加对 配置文件 的引用Imports System.DataImports IDAL '引用接口层'反射+配置文件+抽象工厂实现数据访问Public Class LoginFactory    Private Shared ReadOnly AssemblyName As String = "DAL" '程序集名称    '利用读配置文件可以更改数据库的类型    Dim strDB As String = System.Configuration.ConfigurationSettings.AppSettings("DB")    Public Function CreateIUser() As LoginIUserInfo        Dim classmate As String = AssemblyName + "." + strDB + "LoginDAL" '要实例化的D层的类的名称        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(classmate), LoginIUserInfo) '返回LoginIUserInfo        Return IUser    End FunctionEnd Class

IDAL层

Public Interface LoginIUserInfo    '判断用户名是否正确    Function selectUser(ByVal UserInfo As Entity.LoginUserInfo) As DataTableEnd Interface

DAL层

Imports System.Data.SqlClientPublic Class LoginDAL : Implements IDAL.LoginIUserInfo    '实现接口中方法    Private sqlHelper As New SqlHelper.SqlHelper    '判断用户是否正确    Public Function selectUser(UserInfo As Entity.LoginUserInfo) As DataTable Implements IDAL.LoginIUserInfo.selectUser        Dim sql As String '中间变量，用于存储从数据库中查找到的信息        Dim table As DataTable        '声明并实例化参数数组        Dim sqlParams As SqlParameter() = {New SqlParameter("@userID", UserInfo.UserName), New SqlParameter("@PWD", UserInfo.PassWord)}        sql = "Select * from User_Info where userID=@userID and PWD=@PWD"        '调用SqlHelper类中的GetDataTable（）方法来执行查询，并获取返回值          table = sqlHelper.ExecSelect(sql, CommandType.Text, sqlParams)        Return table    End FunctionEnd Class

SqlHelper层

Imports System.DataImports System.Data.SqlClientImports System.ConfigurationPublic Class SqlHelper    '数据库连接      Dim strConnection As String = "Server=qq;Database=JF;User ID=sa;Password=123456"    Dim conn As New SqlConnection(strConnection)    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        Dim dt As New DataTable        Dim ds As New DataSet        '给cmd赋值          cmd.CommandText = cmdText        cmd.CommandType = cmdType        cmd.Connection = conn        cmd.Parameters.AddRange(paras)  '参数添加          sqlAdapter = New SqlDataAdapter(cmd)  '实例化Adapter          Try            sqlAdapter.Fill(ds)  'dataset填充adapter用             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  '如果cmd命令存在              cmd.Dispose()           '销毁              cmd = Nothing        End If    End SubEnd Class

Entity层

Public Class LoginUserInfo    Private _username As String    Public Property UserName As String  '定义用户名属性        Get            Return _username        End Get        Set(value As String)            _username = value        End Set    End Property    Private _password As String    Public Property PassWord As String   '定义密码属性        Get            Return _password        End Get        Set(value As String)            _password = value        End Set    End PropertyEnd Class

【总结】

七层的路刚刚开始，接下来还有很长一段时间要走，不过一条线走通了，以后就简单了。