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机房收费系统之抽象工厂篇
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??? 機房收費系統vb.net個人版已完成，在此過程中分層的好處在系統的完成過程中得到了很好的體會。第一遍用的是純三層做的，這幾天又在此基礎上又重構了登錄的demo,加上抽象工廠和配置文件的使用。下面以登錄功能為例，總結一下我的機房收費系統。
一、下面看一下我的包圖：
????? 可以看到，這張圖是從最基本的三層UI→BLL→DAL加入設計模式（抽象工廠）演化而來的，采用抽象工廠是考慮到日后更換數據庫的方便。
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二、準備工作
???????創建數據表(課參見實體類中的代碼)
???????創建相應的類庫和窗體。
???????我用的是vb.net的WidowsApplication來添加界面；使用類庫作為其它層的包。
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三、抽象各層的類
??????? 當我們確定了系統的整體架構，就要從宏觀到微觀的實現。
3.1 Entity（實體層）
??????? 數據庫設計好了，我們要根據數據庫中的表抽象實體類，系統中，實體類和表基本上是一一對象的。一個表映射一個實體類，表的字段即為實體類的屬性。
??????? 實體層并不屬于三層的任何一層，它是獨立出來的一層，可以把它看做是自定義變量的組合，供其它三層使用。
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Public?Class?UserInfoEntity???#Region?"定義UserInfo表中各個屬性變量"??????Private?_userName?As?String??????Private?_name?As?String??????Private?_password?As?String??????Private?_userlevel?As?String??????Private?_accountHolder?As?String??????Private?_regDate?As?String??????Private?_regTime?As?String??#End?Region???#Region?"定義數據表中各個字段名常量"??????Private?Const?DBFLELD_USERNAME?=?"userName"??????Private?Const?DBFLELD_NAME?=?"name"??????Private?Const?DBFLELD_PASSWORD?=?"password"??????Private?Const?DBFLELD_USERLEVEL?=?"userLevel"??????Private?Const?DBFLELD_ACCOUNTHOLDER?=?"accountHolder"??????Private?Const?DBFLELD_REGDATE?=?"regDate"??????Private?Const?DBFLELD_TIME?=?"regTime"??#End?Region???#Region?"定義數據表中各個字段參數變量"??????Public?Const?DBPARAM_USERNAME?=?"@userName"??????Public?Const?DBPARAM_NAME?=?"@name"??????Public?Const?DBPARAM_PASSWORD?=?"@password"??????Public?Const?DBPARAM_USERLEVEL?=?"@userLevel"??????Public?Const?DBPARAM_ACCOUNTHOLDER?=?"@accountHolder"??????Public?Const?DBPARAM_REGDATE?=?"@regDate"??????Public?Const?DBPARAM_TIME?=?"@regTime"??#End?Region??????????????????????????????????????Public?Sub?LoadFromDataRow(ByVal?dr?As?DataRow)??????????userName?=?dr(DBFLELD_USERNAME)??????????name?=?dr(DBFLELD_NAME)??????????password?=?dr(DBFLELD_PASSWORD)??????????userlevel?=?dr(DBFLELD_USERLEVEL)??????????accountHolder?=?dr(DBFLELD_ACCOUNTHOLDER)??????????regDate?=?dr(DBFLELD_REGDATE)??????????regTime?=?dr(DBFLELD_TIME)??????End?Sub???#Region?"填充一條記錄"????????????????????????????????????????????????Public?Overloads?Sub?Fill(ByVal?AuserName?As?String,?ByVal?Apassword?As?String,?ByVal?AuserLevel?As?String)??????????userName?=?AuserName??????????password?=?Apassword??????????userlevel?=?AuserLevel??????End?Sub??#End?Region???#Region?"定義數據表中各個屬性"??????????????????????????????????????????Public?Property?userName()?As?String??????????Get??????????????Return?_userName??????????End?Get??????????Set(ByVal?value?As?String)??????????????_userName?=?value??????????End?Set??????End?Property????????????????????????????????????????????Public?Property?name()?As?String??????????Get??????????????Return?_name??????????End?Get??????????Set(ByVal?value?As?String)??????????????_name?=?value??????????End?Set??????End?Property????????????????????????????????????????????Public?Property?password()?As?String??????????Get??????????????Return?_password??????????End?Get??????????Set(ByVal?value?As?String)??????????????_password?=?value??????????End?Set??????End?Property????????????????????????????????????????????Public?Property?userlevel()?As?String??????????Get??????????????Return?_userlevel??????????End?Get??????????Set(ByVal?value?As?String)??????????????_userlevel?=?value??????????End?Set??????End?Property????????????????????????????????????????????Public?Property?accountHolder()?As?String??????????Get??????????????Return?_accountHolder??????????End?Get??????????Set(ByVal?value?As?String)??????????????_accountHolder?=?value??????????End?Set??????End?Property????????????????????????????????????????????Public?Property?regDate()?As?String??????????Get??????????????Return?_regDate??????????End?Get??????????Set(ByVal?value?As?String)??????????????_regDate?=?value??????????End?Set??????End?Property????????????????????????????????????????????Public?Property?regTime()?As?String??????????Get??????????????Return?_regTime??????????End?Get??????????Set(ByVal?value?As?String)??????????????_regTime?=?value??????????End?Set??????End?Property??#End?Region????End?Class??
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?????? 下面是配置文件的使用：在窗體層添加新項目→選中打開窗口的左邊的General選項→添加配置文件，（中間部分是需要手動添加的）。
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<?xml?version="1.0"?encoding="utf-8"??>??<configuration>????????<appSettings?>??????????<add?key="connStr"?value?="Data?Source=.;Initial?Catalog=Login;User?ID=sa;Password=123456"/>??????????<add?key?="AssemblyName"?value?="DAL"/>??????????<add?key?="db"?value?="DB"/>??????</appSettings>????????<startup>??????????<supportedRuntime?version="v4.0"?sku=".NETFramework,Version=v4.0,Profile=Client"?/>??????</startup>??</configuration>??
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3.2 DAL層（數據訪問層）
????接下來我們再看一下數據訪問層（DAL），這一層的主要任務是直接操作數據庫，完成對數據的增刪改查等。這里我們仍然根據數據表來抽象DAL層的類，基本上也是一個表對應一個類，這樣當我們增加新的表，直接增加新的DAL層類就可以，很好地符合了“開閉原則”。
另外，因為DAL層的類是直接對數據庫進行操作的類，所以這個類里封轉大都有四種方法：增刪改查。但根據實際情況會有不同的參數，不同的返回值。
?????? 這里添加了接口層IDAL，利用反射和抽象工廠，以防更換數據庫。
3.2.1 接口層IDAL，添加Entity的引用。
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Imports?Entity????Public?Interface?Iuser??????????????????????????????????????????Function?Check(ByVal?entityUser?As?UserInfoEntity)?As?UserInfoEntity??End?Interface??
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3.2.2 DAL層實現IDAL接口
??????? 下面是DAL層下的DataAccess類
??????? 添加Configuration引用時需從.net子項目中查找，還要添加項目引用Entity和IDAL.
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??Imports?System.Configuration??Imports?System.Reflection??Imports?System.Data.SqlClient??Imports?Entity??Imports?IDAL????Public?Class?DataAccess???#Region?"連接數據庫"??????Private?ReadOnly?connStr?As?String?=?ConfigurationManager.AppSettings("connStr")????????????????????????????????????Public?Overloads?Function?CreateConn()?As?SqlConnection??????????Return?New?SqlConnection(connStr)??????End?Function??#End?Region???#Region?"關閉相關對象"????????????????????????????????????Public?Sub?Close(ByVal?conn?As?SqlConnection)??????????conn.Close()??????????conn?=?Nothing??????End?Sub??????????????????????????????????????Public?Sub?Close(ByVal?cmd?As?SqlCommand)??????????cmd.Dispose()??????????cmd?=?Nothing??????End?Sub??#End?Region????????????????????????????????????????????????????????Public?Sub?AddSqlParameter(ByVal?cmd?As?SqlCommand,?ByVal?dbParam?As?String,?ByVal?dbType?As?SqlDbType,?ByVal?value?As?Object)??????????Dim?sqlParam?As?SqlParameter?=?New?SqlParameter(dbParam,?dbType)??????????sqlParam.Value?=?value??????????cmd.Parameters.Add(sqlParam)??????End?Sub????End?Class??
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??????? DAL層下的DBuser類：
??????? 同樣添加項目引用Entity和IDAL.
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Imports?System.Data.SqlClient??Imports?Entity??Imports?IDAL????Public?Class?DBuser????????????Inherits?DataAccess??????Implements?Iuser????????Public?Function?Check(ByVal?entityUser?As?Entity.UserInfoEntity)?As?UserInfoEntity?Implements?IDAL.Iuser.Check????????????????????Dim?sql?As?String?=?String.Format("select?*?from?userInfo?where?[userName]={0}?and?[password]={1}?and?[userLevel]={2}",?UserInfoEntity.DBPARAM_USERNAME,?UserInfoEntity.DBPARAM_PASSWORD,?UserInfoEntity.DBPARAM_USERLEVEL)??????????Dim?conn?As?SqlConnection?=?CreateConn()??????????Dim?cmd?As?SqlCommand?=?New?SqlCommand(sql,?conn)??????????Dim?sda?As?SqlDataAdapter?=?New?SqlDataAdapter(cmd)??????????Dim?ds?As?New?DataSet??????????????????????AddSqlParameter(cmd,?UserInfoEntity.DBPARAM_USERNAME,?SqlDbType.VarChar,?entityUser.userName)??????????AddSqlParameter(cmd,?UserInfoEntity.DBPARAM_PASSWORD,?SqlDbType.VarChar,?entityUser.password)??????????AddSqlParameter(cmd,?UserInfoEntity.DBPARAM_USERLEVEL,?SqlDbType.VarChar,?entityUser.userlevel)????????????Try??????????????conn.Open()??????????????sda.Fill(ds,?"userInfo")??????????????Dim?dr?As?DataRow?=?ds.Tables("userInfo").Rows(0)??????????????entityUser.LoadFromDataRow(dr)??????????????Return?entityUser??????????Catch?ex?As?Exception??????????????Return?Nothing??????????Finally??????????????Close(cmd)??????????????Close(conn)??????????End?Try??????End?Function??End?Class??
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????? 抽象工廠+反射+配置文件
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Imports?System.Configuration??Imports?System.Reflection??Imports?IDAL????Public?Class?Factory???#Region?"配置加反射"??????Private?Shared?ReadOnly?AssemblyName?As?String?=?ConfigurationManager.AppSettings("AssemblyName")??????Private?Shared?ReadOnly?db?As?String?=?ConfigurationManager.AppSettings("db")????????????????????????????????????Public?Shared?Function?CreateUser()?As?Iuser??????????Dim?ClassName?As?String??????????ClassName?=?AssemblyName?+?"."?+?db?+?"user"??????????Return?CType(Assembly.Load(AssemblyName).CreateInstance(ClassName),?Iuser)??????End?Function??#End?Region????End?Class??
3.BLL層（封裝業務層）：前提添加DAL,IDAL和Entity的引用
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Imports?IDAL??Imports?Entity??Imports?Factory????Public?Class?BllLogin??????????????????????????????????????????Public?Function?CheckRecord(ByVal?entityUserInfo?As?UserInfoEntity)?As?Boolean??????????Dim?checkResult?As?Boolean????????????????????Dim?iuser?As?Iuser????????????????????iuser?=?Factory.Factory.CreateUser()????????????If?Not?IsNothing(iuser.Check(entityUserInfo))?Then??????????????checkResult?=?True??????????Else??????????????checkResult?=?False??????????End?If????????????Return?checkResult??????End?Function??End?Class??
4.UI層（界面層）
??????? ?界面層的類，就是我們窗體類，又多少個 窗體，UI層就有多少個類。
??????? 下面我們看一下登錄窗體類。
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Imports?BLL??Imports?Entity????Public?Class?frmLogin????????????Private?Sub?btnLogin_Click(ByVal?sender?As?System.Object,?ByVal?e?As?System.EventArgs)?Handles?btnLogin.Click????????????????????If?txtUserID.Text?=?""?Then??????????????MessageBox.Show("用戶名不能為空！")??????????????txtUserID.Focus()??????????????Return??????????End?If????????????If?txtPassword.Text?=?""?Then??????????????MessageBox.Show("用戶名不能為空！")??????????????txtPassword.Focus()??????????????Return??????????End?If??????????????????????Dim?entityUserInfo?As?New?UserInfoEntity??????????entityUserInfo.Fill(Trim(txtUserID.Text),?Trim(txtPassword.Text),?Trim(cboUserLevel.Text))??????????????????????Dim?bllUserInfo?As?New?BllLogin??????????If?bllUserInfo.CheckRecord(entityUserInfo)?Then??????????????Me.Hide()??????????????frmMain.Show()????????????????????????????????????????????????????????????????????Else??????????????MsgBox("登錄失敗",?vbOKOnly?+?vbInformation,?"登錄失敗")??????????????txtUserID.Focus()??????????????Exit?Sub??????????End?If??????End?Sub??????????????Private?Sub?btnCancel_Click(ByVal?sender?As?System.Object,?ByVal?e?As?System.EventArgs)?Handles?btnCancel.Click??????????Me.Close()??????End?Sub????End?Class??
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??????? 上面就是我在三層（UI→BLL→DAL）的基礎上加上設計模式抽象工程實現系統登錄的Demo，拿出來和大家一起分享，其中的不足之處，還希望大家多多指正。
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