机房收费系统重构之七层系统登录

1.无论是对是错先学习前人的经验通过博客，一个功能至少看三人以上看其相同的地方并质疑其不同的地方

2.先敲出一条线（就是一个功能），能够自己敲最好，不能就借鉴前人，然后走一遍弄清其基本思想逻辑

3.及时总结并一个功能相继实现

什么是七层登录？

首先三层登录是U层获取界面信息，到B层根据业务需要进行逻辑判断做出相应的处理，B层进行整个操作所需的数据都要到D层进行数据的提取通过数据库，三层登录环环相扣，对于高内聚低耦合的原则是相悖的，于是就通过一些方式来对三层进行解耦，最后正好是七层（除SQLhelper外），所以便是七层登录，用到了两个设计模式facade（外观模式）

和factory（抽象工厂模式），解耦后的七层便是UI层、Facade层、BLL层、Factory层、I层（接口层）、DAL层、Entity（实体层）

Facade层：解耦了U层和B层，这样便减弱了两个类之间的关联，提高了代码的可维护性，这样无论U层和F层进行什么的改变只需去外观层进行相应的改动便可

Factory层：通过配置文件来选取相应的数据库，创建相应数据库接口，解耦了数据库的类型

IDAL层：D层通过创建的接口来输送B层所需要的数据，B层获取数据也要通过这个接口

通过图可知七层的引用关系为：

U层：Facade层和Entity层；Facade层：BLL层和Entity层；BLL层：Factory层和IDAL层和Entity层；

Factory层：IDAL层和Entity层；IDAL层：Entity层；DAL：实现IDAL并引用Entity层

为什么使用七层？

使用三层也可以实现系统的功能，然而这只是做到了面向对象的初步工作，我们做完一个系统更注重的是后期的不断完善与维护，如果前期不能很好的做到高内聚低耦合那么后期维护便是牵一发而动全身，工作量之大往往得不偿失，这便是软件危机的一种表现，使用七层便很好的做到了未雨绸缪，即使用七层不是为了做出系统而是为了做出能够简便地不断更新和维护的系统

七层是如何实现的？

下面以机房收费系统登录为例

UI层：用户给出相应的操作和数据，传递给Facade层，通过里面的方法去和BLL层进行交互

Public Class frmLogin

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

        '进行输入框判断
        If txtUserName.Text = "" Then
            MessageBox.Show("请输入用户名！", "", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
            txtUserName.Focus()

        ElseIf txtPassWord.Text = "" Then
            MessageBox.Show("请输入密码！", "", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
            txtPassWord.Focus()
        End If

        '实例化所需要的各层的类

        Dim FacodeLogin As New Facade.LoginFAC
        Dim UserInfo As New Entity.EntityUsersWork

        '如果执行验证的时候有错误将给出相应的处理
        Try

            UserInfo.userID = txtUserName.Text.Trim()
            UserInfo.pwd = txtPassWord.Text
            Dim strResult As Boolean
            '将U层的用户信息传给外观层
            strResult = FacodeLogin.CheckUser(UserInfo) '判断用户是否存在
            If strResult = False Then
                MsgBox("用户名不存在！", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
                txtUserName.Text = ""
                txtPassWord.Text = ""
                txtUserName.Select()
                txtUserName.Focus()

            End If
            Dim table As DataTable
            table = FacodeLogin.CheckPwd(UserInfo)
            If Trim(txtPassWord.Text) = Trim(table.Rows(0).Item(1)) Then
                'MsgBox("登录成功！")
                frmMain.Show()
                Me.Hide()
                txtPassWord.Text = ""
                txtUserName.Text = ""

            End If
            '出现验证从错误给出的相应处理
        Catch ex As Exception
            MsgBox("用户不存在或者密码不正确")
            txtUserName.Text = ""
            txtPassWord.Text = ""
            txtUserName.Select()
            txtUserName.Focus()
        End Try

    End Sub
End Class

Facade层：通过封装的方法去调用BLL层的对应具体业务逻辑，通过这个业务逻辑到D层里进行数据验证返回要验证的对象信息

Public Class LoginFAC
    '检查用户名是否存在
    Public Function CheckUser(ByVal UserInfo As Entity.EntityUsersWork) As Boolean
        Dim IsUserExist As New BLL.UsersBLL
        Dim result As Boolean
        result = IsUserExist.CheckUser(UserInfo)

        If result = True Then
            Return True
        Else
            Return False
        End If
    End Function

    '检查密码是否正确
    Public Function CheckPwd(ByVal UserInfo As Entity.EntityUsersWork) As DataTable
        Dim IsPwdExist As New BLL.UsersBLL
        Dim table As DataTable
        table = IsPwdExist.CheckPwd(UserInfo)
        Return table
    End Function
End Class

BLL层：通过

Imports IDAL
Public Class UsersBLL
    '检验用户是否存存在的业务逻辑
    Public Function CheckUser(ByVal UserInfo As Entity.EntityUsersWork) As Boolean
        Dim Factory As New Factory.FactoryDB
        Dim IUser As IDAL.IUser
        '调用创建用户的工厂方法
        IUser = Factory.CreateIUser() '调用工厂的create Iuser方法创建Iuser接口实例
        Dim table As New DataTable
        Dim result As Boolean
        table = IUser.selectUser(UserInfo)

        '进行用户是否存在的判断
        If table.Rows.Count = 0 Then '此判断是什么意思？？
            result = False
        Else
            result = True
        End If
        Return result
    End Function

    '检验用户登录密码是否正确的业务逻辑
    Public Function CheckPwd(ByVal UserInfo As Entity.EntityUsersWork) As DataTable
        Dim Factory As New Factory.FactoryDB
        Dim Iuser As IDAL.IUser
        Dim table As DataTable

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

Factory层：

Imports IDAL '引用接口层
'反射+配置文件+抽象工厂时间书库空访问
Public Class FactoryDB
    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.ConfigurationManager.AppSettings("DB")
    Public Function CreateIUser() As IUser
        Dim classname As String = AssemblyName + "." + strDB + "UserDAL"
        Dim IUser As IUser
        'CType函数将返回表达式显示地转换为指定的数据类型、对象、结构、类或接口的结果
        IUser = CType(Assembly.Load(AssemblyName).CreateInstance(classname), IUser)
        Return IUser
    End Function
End Class

Iuser层：

Imports System.Data
Imports System.Data.SqlClient
Public Class SqlUserDAL : Implements IDAL.IUser
    '实现接口中的方法
    Private sqlHelper As New SQLHelp.sqlHelper
    '判断用户是否存在
    Public Function selectUser(UserInfo As Entity.EntityUsersWork) As DataTable Implements IDAL.IUser.selectUser
        Dim sql As String  '中间变量，用于存储从数据库中查找的信息
        Dim table As DataTable


        '声明并实例化参数数组
        Dim sqlParams As SqlParameter() = {New SqlParameter("@userID", UserInfo.userID), New SqlParameter("@pwd", UserInfo.pwd)}
        sql = "select * from userwork_Info where userID = @userID and pwd = @pwd"
        '调取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

DAL层

Imports System.Data
Imports System.Data.SqlClient
Public Class SqlUserDAL : Implements IDAL.IUser
    '实现接口中的方法
    Private sqlHelper As New SQLHelp.sqlHelper
    '判断用户是否存在
    Public Function selectUser(UserInfo As Entity.EntityUsersWork) As DataTable Implements IDAL.IUser.selectUser
        Dim sql As String  '中间变量，用于存储从数据库中查找的信息
        Dim table As DataTable


        '声明并实例化参数数组
        Dim sqlParams As SqlParameter() = {New SqlParameter("@userID", UserInfo.userID), New SqlParameter("@pwd", UserInfo.pwd)}
        sql = "select * from userwork_Info where userID = @userID and pwd = @pwd"
        '调取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

Entity层：

Public Class EntityUsersWork
    '设置用户名属性
    Private _userID As String

    Public Property userID As String
        Get
            Return _userID
        End Get
        Set(value As String)
            _userID = value
        End Set
    End Property

    '设置密码属性
    Private _pwd As String

    Public Property pwd As String
        Get
            Return _pwd
        End Get
        Set(value As String)
            _pwd = value
        End Set
    End Property

    '设置等级属性
    Private _level As String

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

    '设置用户姓名属性
    Private _name As String

    Public Property name As String
        Get
            Return _name
        End Get
        Set(value As String)
            _name = value
        End Set
    End Property

    '设置开户人属性
    Private _head As String

    Public Property head As String
        Get
            Return _head
        End Get
        Set(value As String)
            _head = value
        End Set
    End Property

    '设置日期属性
    Private _date As Date
    Public Property Logindate As Date
        Get
            Return _date
        End Get
        Set(value As Date)
            _date = value
        End Set
    End Property

    '设置时间属性
    Private _time As TimeZone

    Public Property Logintime As TimeZone
        Get
            Return _time
        End Get
        Set(value As TimeZone)
            _time = value
        End Set
    End Property

    '设置电脑属性
    Private _computer As String

    Public Property Usecomputer As String
        Get
            Return _computer
        End Get
        Set(value As String)
            _computer = value
        End Set
    End Property

    '设置修改密码属性
    Private _oldpwd As String

    Public Property oldpwd As String
        Get
            Return _oldpwd
        End Get
        Set(value As String)
            _oldpwd = value
        End Set
    End Property

    '设置状态属性
    Private _status As String
    Public Property status As String
        Get
            Return _status
        End Get
        Set(value As String)
            _status = value
        End Set
    End Property
End Class

一般七层登录如果不用到配置文件和sqlhelper类就可以了，即把上面和配置文件+反射与sqlhelper相关的代码直接去掉就行，为了使类在解耦时更好的得到封装和减少代码的重复量便用到了配置文件和sqlhelper

配置文件：