PetShop的三层架构介绍.03

实际项目架构

如下是一个实际项目架构图形例子：

图形符号含义，实线+空心三角：代表泛化(据说泛化包含继承和实现)。

虚线+空心三角：代表实现，这里我更愿意用"实现符号"代替"泛化符号",下图是我设计时忘了把实线转换成虚线了。

虚线+箭头：代表依赖。

.从UI层开始

一个设定会员号密码的例子：

UserPwd.aspx.cs(UI层调用BLL层)

......
using ReflectionFactory;
using IBLL;
using Model;
using System.Collections.Generic;

public partial class AdminClient_UserPwd : System.Web.UI.Page
{
    private static CompanyInfo companyInfo = new CompanyInfo();//实例化实体类对象
    private static UserInfo userInfo = new UserInfo();//实例化实体类对象UserInfo
    //引用一个企业服务接口，在这里反射工厂(也就是IoC容器)会把企业服务类的实例化对象
    //初始化给该企业服务接口。
    private static readonly ICompanyBLL companyBLL = BLLFactory.CreateCompanyBLL();
    //同上，这里注入的是一个会员服务类的具体实现。
    private static readonly IUserBLL userBLL = BLLFactory.CreateUserBLL();
    protected void Page_Load(object sender, EventArgs e){...}

    protected void btn_ResetClick(object sender, EventArgs e)
    {//调用企业服务companyBLL的具体方法、会员服务userBLL的具体方法 
        if (string.IsNullOrEmpty(this.txt_NewPwd.Value)) return;
        //按CoID找出 会员号
        companyInfo.CoID = Convert.ToInt32(Request.QueryString["CompanyID"]);
        IList<CompanyInfo> companyIL = companyBLL.GetCompany1(companyInfo);
        userInfo.UserAccount = companyIL[0].CoUserAccount;
        companyIL.Clear();
        //更新该会员号的密码
        userInfo.UserPwd = this.txt_NewPwd.Value;
        if (userBLL.UpdateUserPwd(userInfo))
        {
            Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "", 
"alert('修改成功！');window.location.href=location.href;", true); return;
        }
    }
}

.上面例子引出了反射工厂机制

1.BLLFactory.cs和DALFactory.cs

BLLFactory.cs:BLL层各个类的反射注入工厂

...
using IBLL;

namespace ReflectionFactory
{
    /// <summary>业务逻辑层工厂，用于获取相应的业务逻辑层对象</summary>
    public sealed class BLLFactory
    {
        /// <summary>
        /// 获取会员模块 逻辑业务层对象
        /// </summary>
        public static IUserBLL CreateUserBLL()
        {
            return (IUserBLL)DependencyInjector.GetBLLObject("UserBLL");
        }

         //更多模块...
         ...
    }
}

DALFactory.cs:DAL层各个类的反射注入工厂

...
using IDAL;

namespace ReflectionFactory
{
    ///<summary>数据访问层工厂，用于获取相应的数据访问层对象</summary>
    public sealed class DALFactory
    {
         /// <summary>
         /// 获取会员模块 数据访问层对象
         /// </summary>
         /// <returns></returns>
         public static IUserDAL CreateUserDAL()
         {
             return (IUserDAL)DependencyInjector.GetDALObject("UserDAL");
         }

          //更多模块...
          ...
     }
}

2.反射机制=反射+Web.config

BLLFactory.cs和DALFactory.cs调用DependencyInjector.cs

DependencyInjector.cs:依赖注入的提供者，使用反射机制实现

代码

using System;
using System.Collections.Generic;
using System.Text;
using System.Web;
using System.Web.Caching;
using System.Configuration;
using System.Reflection;
using Common;

namespace ReflectionFactory
{
    /// <summary>
    /// 依赖注入提供者
    /// 使用反射机制实现
    /// </summary>
    public sealed class DependencyInjector
    {
        /// <summary>
        /// 取得数据访问层对象
        /// 首先检查缓存中是否存在，如果不存在，则利用反射机制返回对象
        /// </summary>
        /// <param name="className">数据访问类名称</param>
        /// <returns>数据访问层对象</returns>
        public static object GetDALObject(string className)
        {
            ///取得数据访问层名称，首先检查缓存，不存在则到配置文件中读取
            ///缓存依赖项为Web.config文件
            object dal = CacheAccess.GetFromCache("DAL");
            if (dal == null)
            {
                CacheDependency fileDependency = new CacheDependency(
                    HttpContext.Current.Server.MapPath("Web.config"));
                dal = ConfigurationManager.AppSettings["DAL"];
                CacheAccess.SaveToCache("DAL", dal, fileDependency);
            }

            ///取得数据访问层对象
            string dalName = (string)dal;
            string fullClassName = dalName + "." + className;
            object dalObject = CacheAccess.GetFromCache(className);
            if (dalObject == null)
            {
                CacheDependency fileDependency = new CacheDependency(
                    HttpContext.Current.Server.MapPath("Web.config"));
                dalObject = Assembly.Load(dalName).CreateInstance(fullClassName);
                CacheAccess.SaveToCache(className, dalObject, fileDependency);
            }
            return dalObject;
        }

        /// <summary>
        /// 取得业务逻辑层对象
        /// 首先检查缓存中是否存在，如果不存在，则利用反射机制返回对象
        /// </summary>
        /// <param name="className">业务逻辑类名称</param>
        /// <returns>业务逻辑层对象</returns>
        public static object GetBLLObject(string className)
        {
            ///取得业务逻辑层名称，首先检查缓存，不存在则到配置文件中读取
            ///缓存依赖项为Web.config文件
            object bll = CacheAccess.GetFromCache("BLL");
            if (bll == null)
            {
                CacheDependency fileDependency = new CacheDependency(
                    HttpContext.Current.Server.MapPath("Web.config"));
                bll = ConfigurationManager.AppSettings["BLL"];
                CacheAccess.SaveToCache("BLL", bll, fileDependency);
            }

            ///取得业务逻辑层对象
            string bllName = (string)bll;
            string fullClassName = bllName + "." + className;
            object bllObject = CacheAccess.GetFromCache(className);
            if (bllObject == null)
            {
                CacheDependency fileDependency = new CacheDependency(
                    HttpContext.Current.Server.MapPath("Web.config"));
                bllObject = Assembly.Load(bllName).CreateInstance(fullClassName);
                CacheAccess.SaveToCache(className, bllObject, fileDependency);
            }

            return bllObject;
        }
    }
}

Web.config:UI层配置文件

<configuration>
    <appSettings>
        <add key="DAL" value="DAL.SOL"/>
        <add key="BLL" value="BLL.SOL"/>
    </appSettings>
    <connectionStrings>

3.DependencyInjector.cs调用到Common辅助类模块中的CacheAccess.cs类

代码

using System;
using System.Collections.Generic;
using System.Text;
using System.Web;
using System.Web.Caching;

namespace Common
{
    /// <summary>
    /// 辅助类，用于缓存操作
    /// </summary>
    public sealed class CacheAccess
    {
        /// <summary>
        /// 将对象加入到缓存中
        /// </summary>
        /// <param name="cacheKey">缓存键</param>
        /// <param name="cacheObject">缓存对象</param>
        /// <param name="dependency">缓存依赖项</param>
        public static void SaveToCache(string cacheKey, object cacheObject,
            CacheDependency dependency)
        {
            Cache cache = HttpRuntime.Cache;
            cache.Insert(cacheKey, cacheObject, dependency);
        }

        /// <summary>
        /// 从缓存中取得对象，不存在则返回null
        /// </summary>
        /// <param name="cacheKey">缓存键</param>
        /// <returns>获取的缓存对象</returns>
        public static object GetFromCache(string cacheKey)
        {
            Cache cache = HttpRuntime.Cache;
            return cache[cacheKey];
        }
    }
}

.讲述BLL层的故事

BLL业务逻辑层模块如何"实现"IBLL接口族模块，且"调用DAL数据访问层模块"？

UserBLL.cs:BLL层的会员类

...
using ReflectionFactory;
using IBLL;
using Model;
using IDAL;
using Common;

namespace BLL
{
    public class UserBLL:IUserBLL
    {
        private static readonly IUserDAL userDAL = DALFactory.CreateUserDAL();

        /// <summary>
        /// Tb_User更新会员密码
        /// </summary>
        public bool UpdateUserPwd(UserInfo user)
        {
            return userDAL.UpdateUserPwd(user);
        }

        //更多方法...
    }
}

IUserBLL.cs:BLL层的会员类接口

...
using Model;

namespace IBLL
{
    public interface IUserBLL
    {
        /// <summary>
        /// Tb_User更新会员密码
        /// </summary>
        bool UpdateUserPwd(UserInfo user);

        //更多方法...
    }
}

IUserDAL.cs:DAL层的会员类接口

...
using Model;

namespace IDAL
{
    public interface IUserDAL
    {
        /// <summary>
        /// Tb_User更新会员密码
        /// </summary>
        bool UpdateUserPwd(UserInfo user);

        //更多方法...
    }
}

.DAL层的精彩

代码

...
using System.Data;
using System.Data.SqlClient;
using IDAL;
using DBUtility;
using Model;
using Common;

namespace DAL
{
    public class UserDAL : IUserDAL
    {
        private const string SQL_UPDATE_PASSWORD = "UPDATE Tb_User SET UserPwd=@UserPwd WHERE UserAccount=@UserAccount;";
        //更多T-SQL语句...

        private const string PARM_UserPwd = "@UserPwd";
        private const string PARM_UserAccount = "@UserAccount";
        //更多参数化查询参数...

        /// <summary>
        /// Tb_User更新会员密码
        /// </summary>
        public bool UpdateUserPwd(UserInfo user)
        {
            SqlParameter[] parms = new SqlParameter[]{
                new SqlParameter(PARM_UserPwd,SqlDbType.VarChar,50),
                new SqlParameter(PARM_UserAccount,SqlDbType.VarChar,50)
            };
            parms[0].Value = user.UserPwd;
            parms[1].Value = user.UserAccount;
            if (SqlHelper.ExecuteNonQuery(SqlHelper.connString, CommandType.Text, SQL_UPDATE_PASSWORD, parms) > 0)
            {
                return true;
            }
            else { return false; }
        }

         //更多方法...
    }
}

UserDAL.cs类涉及到"参数化查询"和对"DBUtility类"的调用，DBUtility模块主要就是微软的那个SQLHelper.cs，请自行上网搜索下载。

这里简述一下参数化查询：

private const string SQL_UPDATE_PASSWORD = 
"UPDATE Tb_User SET UserPwd=@UserPwd WHERE UserAccount=@UserAccount;";

@UserPwd、@UserAccount对应T-SQL语句中的变量；

private const string PARM_UserPwd = "@UserPwd";
private const string PARM_UserAccount = "@UserAccount";

PARM_UserPwd、PARM_UserAccount是C#中的变量，对应于T-SQL语句中的@UserPwd、@UserAccount;

在程序中是把变量值传递给@UserPwd、@UserAccount的媒介。

 /// <summary>
/// Tb_User更新会员密码
/// </summary>
 public bool UpdateUserPwd(UserInfo user)
{
    SqlParameter[] parms = new SqlParameter[]{
        new SqlParameter(PARM_UserPwd,SqlDbType.VarChar,50),
        new SqlParameter(PARM_UserAccount,SqlDbType.VarChar,50)
    };
    parms[0].Value = user.UserPwd;
    parms[1].Value = user.UserAccount;
    if (SqlHelper.ExecuteNonQuery(SqlHelper.connString, 
CommandType.Text, SQL_UPDATE_PASSWORD, parms) > 0)
    {
        return true;
    }
    else { return false; }
}