技术开发 频道

数据库瓶颈非常好的良药:web三层架构

  【IT168技术】LINQ语言集成查询是微软用于抗衡竞争对手,改进现有开发模式下面向数据库操作问题的一个种全新体系架构。它的出现,解决了面向对象开发中由数据库操作引起的先天性的瓶颈,使得面向对象和数据库完美结合,程序员不再受限于复杂的SQL脚本,而可以一种近乎完美的方式来搭建自己的面向对象型软件系统,这种方式就是将数据完全对象化,将SQL语句封装到底层,由framework来完成,程序员只需面向数据库对象来编程,从另一种意义上来说,是把数据也程序化了。

  LINQ的这种开发模式也改变了系统架构的搭建方式,在以往的系统中,数据访问层DAL要访问数据字段,业务逻辑层BLL要得到数据都需要通过数据模型层Model来处理,而LINQ和VS2008为我们带来了一种全新的自动化方式生成数据模型层,这就是dbml(Database Mark Language。数据库描述语言,是一种xml格式的文档,用来描述数据库),有了它我们就不需要去找那些第三方的代码生成工具,只需要把数据表拖拽到设计器中,如下图所示,DONET便为我们做好了一切。

  完成拖拽操作后,VS会自动生成一个数据模型层的dbml文件和相关的类文件。这样我们省去了数据模型层的搭建,系统的架构也就有所不同,以下用一个例子简单的讲一下该架构模型。

  为了完成这个架构,我们首先要创建一个WEB APPLICATION项目,在新建项目窗口选择“ASP.NET WEB应用程序”,为它取一个名字,并确定。

  接下来,在解决方案资源管理器中再添加一个类库项目,取名为DAL,如下图:

  再使用同样的方法在解决方案资源管理器中添加一个类库项目,取名为BLL,这样我们的基础架构搭建完成,此时我们的解决方案资源管理器应该是如下结构。

  此时,我们先从DAL项目入手,在DAL项目中,添加一个LINQ TO SQL类,取名为Northwind(为了方便起见,此项目使用SQL SERVER2005中的Northwind示例数据库),双击新建立的Northwind.dbml文件,然后打开“服务器资源管理器”,建立与数据的连接,并从Northwind数据库中,将Employees表拖拽到Northwind.dbml文件的可视化设计器中。

    

  初始的Northwind.dbml文件代码如下:

#pragma warning disable 1591
//------------------------------------------------------------------------------
// <auto-generated>
//     此代码由工具生成。
//     运行时版本:2.0.50727.3053
//
//     对此文件的更改可能会导致不正确的行为,并且如果
//     重新生成代码,这些更改将会丢失。
// </auto-generated>
//------------------------------------------------------------------------------

namespace DAL
{
    using System.Data.Linq;
    using System.Data.Linq.Mapping;
    using System.Data;
    using System.Collections.Generic;
    using System.Reflection;
    using System.Linq;
    using System.Linq.Expressions;
    using System.ComponentModel;
    using System;
    
    
    [System.Data.Linq.Mapping.DatabaseAttribute(Name
="Northwind")]
    
public partial class NorthwindDataContext : System.Data.Linq.DataContext
    {
        
        
private static System.Data.Linq.Mapping.MappingSource mappingSource = new AttributeMappingSource();
        
    #region Extensibility Method Definitions
    partial
void OnCreated();
    partial
void InsertEmployees(Employees instance);
    partial
void UpdateEmployees(Employees instance);
    partial
void DeleteEmployees(Employees instance);
    #endregion
        
        
public NorthwindDataContext() :
                base(global::DAL.Properties.Settings.Default.NorthwindConnectionString, mappingSource)
        {
            OnCreated();
        }
        
        
public NorthwindDataContext(string connection) :
                base(connection, mappingSource)
        {
            OnCreated();
        }
        
        
public NorthwindDataContext(System.Data.IDbConnection connection) :
                base(connection, mappingSource)
        {
            OnCreated();
        }
        
        
public NorthwindDataContext(string connection, System.Data.Linq.Mapping.MappingSource mappingSource) :
                base(connection, mappingSource)
        {
            OnCreated();
        }
        
        
public NorthwindDataContext(System.Data.IDbConnection connection, System.Data.Linq.Mapping.MappingSource mappingSource) :
                base(connection, mappingSource)
        {
            OnCreated();
        }
        
        
public System.Data.Linq.Table<Employees> Employees
        {
            get
            {
                
return this.GetTable<Employees>();
            }
        }
    }
    
    [Table(Name
="dbo.Employees")]
    
public partial class Employees : INotifyPropertyChanging, INotifyPropertyChanged
    {
        
        
private static PropertyChangingEventArgs emptyChangingEventArgs = new PropertyChangingEventArgs(String.Empty);
        
        
private int _EmployeeID;
        
        
private string _LastName;
        
        
private string _FirstName;
        
        
private string _Title;
        
        
private string _TitleOfCourtesy;
        
        
private System.Nullable<System.DateTime> _BirthDate;
        
        
private System.Nullable<System.DateTime> _HireDate;
        
        
private string _Address;
        
        
private string _City;
        
        
private string _Region;
        
        
private string _PostalCode;
        
        
private string _Country;
        
        
private string _HomePhone;
        
        
private string _Extension;
        
        
private System.Data.Linq.Binary _Photo;
        
        
private string _Notes;
        
        
private System.Nullable<int> _ReportsTo;
        
        
private string _PhotoPath;
        
    #region Extensibility Method Definitions
    partial
void OnLoaded();
    partial
void OnValidate(System.Data.Linq.ChangeAction action);
    partial
void OnCreated();
    partial
void OnEmployeeIDChanging(int value);
    partial
void OnEmployeeIDChanged();
    partial
void OnLastNameChanging(string value);
    partial
void OnLastNameChanged();
    partial
void OnFirstNameChanging(string value);
    partial
void OnFirstNameChanged();
    partial
void OnTitleChanging(string value);
    partial
void OnTitleChanged();
    partial
void OnTitleOfCourtesyChanging(string value);
    partial
void OnTitleOfCourtesyChanged();
    partial
void OnBirthDateChanging(System.Nullable<System.DateTime> value);
    partial
void OnBirthDateChanged();
    partial
void OnHireDateChanging(System.Nullable<System.DateTime> value);
    partial
void OnHireDateChanged();
    partial
void OnAddressChanging(string value);
    partial
void OnAddressChanged();
    partial
void OnCityChanging(string value);
    partial
void OnCityChanged();
    partial
void OnRegionChanging(string value);
    partial
void OnRegionChanged();
    partial
void OnPostalCodeChanging(string value);
    partial
void OnPostalCodeChanged();
    partial
void OnCountryChanging(string value);
    partial
void OnCountryChanged();
    partial
void OnHomePhoneChanging(string value);
    partial
void OnHomePhoneChanged();
    partial
void OnExtensionChanging(string value);
    partial
void OnExtensionChanged();
    partial
void OnPhotoChanging(System.Data.Linq.Binary value);
    partial
void OnPhotoChanged();
    partial
void OnNotesChanging(string value);
    partial
void OnNotesChanged();
    partial
void OnReportsToChanging(System.Nullable<int> value);
    partial
void OnReportsToChanged();
    partial
void OnPhotoPathChanging(string value);
    partial
void OnPhotoPathChanged();
    #endregion
        
        
public Employees()
        {
            OnCreated();
        }
        
        [Column(Storage
="_EmployeeID", DbType="Int NOT NULL", IsPrimaryKey=true)]
        
public int EmployeeID
        {
            get
            {
                
return this._EmployeeID;
            }
            set
            {
                
if ((this._EmployeeID != value))
                {
                    
this.OnEmployeeIDChanging(value);
                    
this.SendPropertyChanging();
                    
this._EmployeeID = value;
                    
this.SendPropertyChanged("EmployeeID");
                    
this.OnEmployeeIDChanged();
                }
            }
        }
        
        [Column(Storage
="_LastName", DbType="NVarChar(20) NOT NULL", CanBeNull=false)]
        
public string LastName
        {
            get
            {
                
return this._LastName;
            }
            set
            {
                
if ((this._LastName != value))
                {
                    
this.OnLastNameChanging(value);
                    
this.SendPropertyChanging();
                    
this._LastName = value;
                    
this.SendPropertyChanged("LastName");
                    
this.OnLastNameChanged();
                }
            }
        }
        
        [Column(Storage
="_FirstName", DbType="NVarChar(10) NOT NULL", CanBeNull=false)]
        
public string FirstName
        {
            get
            {
                
return this._FirstName;
            }
            set
            {
                
if ((this._FirstName != value))
                {
                    
this.OnFirstNameChanging(value);
                    
this.SendPropertyChanging();
                    
this._FirstName = value;
                    
this.SendPropertyChanged("FirstName");
                    
this.OnFirstNameChanged();
                }
            }
        }
        
        [Column(Storage
="_Title", DbType="NVarChar(30)")]
        
public string Title
        {
            get
            {
                
return this._Title;
            }
            set
            {
                
if ((this._Title != value))
                {
                    
this.OnTitleChanging(value);
                    
this.SendPropertyChanging();
                    
this._Title = value;
                    
this.SendPropertyChanged("Title");
                    
this.OnTitleChanged();
                }
            }
        }
        
        [Column(Storage
="_TitleOfCourtesy", DbType="NVarChar(25)")]
        
public string TitleOfCourtesy
        {
            get
            {
                
return this._TitleOfCourtesy;
            }
            set
            {
                
if ((this._TitleOfCourtesy != value))
                {
                    
this.OnTitleOfCourtesyChanging(value);
                    
this.SendPropertyChanging();
                    
this._TitleOfCourtesy = value;
                    
this.SendPropertyChanged("TitleOfCourtesy");
                    
this.OnTitleOfCourtesyChanged();
                }
            }
        }
        
        [Column(Storage
="_BirthDate", DbType="DateTime")]
        
public System.Nullable<System.DateTime> BirthDate
        {
            get
            {
                
return this._BirthDate;
            }
            set
            {
                
if ((this._BirthDate != value))
                {
                    
this.OnBirthDateChanging(value);
                    
this.SendPropertyChanging();
                    
this._BirthDate = value;
                    
this.SendPropertyChanged("BirthDate");
                    
this.OnBirthDateChanged();
                }
            }
        }
        
        [Column(Storage
="_HireDate", DbType="DateTime")]
        
public System.Nullable<System.DateTime> HireDate
        {
            get
            {
                
return this._HireDate;
            }
            set
            {
                
if ((this._HireDate != value))
                {
                    
this.OnHireDateChanging(value);
                    
this.SendPropertyChanging();
                    
this._HireDate = value;
                    
this.SendPropertyChanged("HireDate");
                    
this.OnHireDateChanged();
                }
            }
        }
        
        [Column(Storage
="_Address", DbType="NVarChar(60)")]
        
public string Address
        {
            get
            {
                
return this._Address;
            }
            set
            {
                
if ((this._Address != value))
                {
                    
this.OnAddressChanging(value);
                    
this.SendPropertyChanging();
                    
this._Address = value;
                    
this.SendPropertyChanged("Address");
                    
this.OnAddressChanged();
                }
            }
        }
        
        [Column(Storage
="_City", DbType="NVarChar(15)")]
        
public string City
        {
            get
            {
                
return this._City;
            }
            set
            {
                
if ((this._City != value))
                {
                    
this.OnCityChanging(value);
                    
this.SendPropertyChanging();
                    
this._City = value;
                    
this.SendPropertyChanged("City");
                    
this.OnCityChanged();
                }
            }
        }
        
        [Column(Storage
="_Region", DbType="NVarChar(15)")]
        
public string Region
        {
            get
            {
                
return this._Region;
            }
            set
            {
                
if ((this._Region != value))
                {
                    
this.OnRegionChanging(value);
                    
this.SendPropertyChanging();
                    
this._Region = value;
                    
this.SendPropertyChanged("Region");
                    
this.OnRegionChanged();
                }
            }
        }
        
        [Column(Storage
="_PostalCode", DbType="NVarChar(10)")]
        
public string PostalCode
        {
            get
            {
                
return this._PostalCode;
            }
            set
            {
                
if ((this._PostalCode != value))
                {
                    
this.OnPostalCodeChanging(value);
                    
this.SendPropertyChanging();
                    
this._PostalCode = value;
                    
this.SendPropertyChanged("PostalCode");
                    
this.OnPostalCodeChanged();
                }
            }
        }
        
        [Column(Storage
="_Country", DbType="NVarChar(15)")]
        
public string Country
        {
            get
            {
                
return this._Country;
            }
            set
            {
                
if ((this._Country != value))
                {
                    
this.OnCountryChanging(value);
                    
this.SendPropertyChanging();
                    
this._Country = value;
                    
this.SendPropertyChanged("Country");
                    
this.OnCountryChanged();
                }
            }
        }
        
        [Column(Storage
="_HomePhone", DbType="NVarChar(24)")]
        
public string HomePhone
        {
            get
            {
                
return this._HomePhone;
            }
            set
            {
                
if ((this._HomePhone != value))
                {
                    
this.OnHomePhoneChanging(value);
                    
this.SendPropertyChanging();
                    
this._HomePhone = value;
                    
this.SendPropertyChanged("HomePhone");
                    
this.OnHomePhoneChanged();
                }
            }
        }
        
        [Column(Storage
="_Extension", DbType="NVarChar(4)")]
        
public string Extension
        {
            get
            {
                
return this._Extension;
            }
            set
            {
                
if ((this._Extension != value))
                {
                    
this.OnExtensionChanging(value);
                    
this.SendPropertyChanging();
                    
this._Extension = value;
                    
this.SendPropertyChanged("Extension");
                    
this.OnExtensionChanged();
                }
            }
        }
        
        [Column(Storage
="_Photo", DbType="Image", UpdateCheck=UpdateCheck.Never)]
        
public System.Data.Linq.Binary Photo
        {
            get
            {
                
return this._Photo;
            }
            set
            {
                
if ((this._Photo != value))
                {
                    
this.OnPhotoChanging(value);
                    
this.SendPropertyChanging();
                    
this._Photo = value;
                    
this.SendPropertyChanged("Photo");
                    
this.OnPhotoChanged();
                }
            }
        }
        
        [Column(Storage
="_Notes", DbType="NText", UpdateCheck=UpdateCheck.Never)]
        
public string Notes
        {
            get
            {
                
return this._Notes;
            }
            set
            {
                
if ((this._Notes != value))
                {
                    
this.OnNotesChanging(value);
                    
this.SendPropertyChanging();
                    
this._Notes = value;
                    
this.SendPropertyChanged("Notes");
                    
this.OnNotesChanged();
                }
            }
        }
        
        [Column(Storage
="_ReportsTo", DbType="Int")]
        
public System.Nullable<int> ReportsTo
        {
            get
            {
                
return this._ReportsTo;
            }
            set
            {
                
if ((this._ReportsTo != value))
                {
                    
this.OnReportsToChanging(value);
                    
this.SendPropertyChanging();
                    
this._ReportsTo = value;
                    
this.SendPropertyChanged("ReportsTo");
                    
this.OnReportsToChanged();
                }
            }
        }
        
        [Column(Storage
="_PhotoPath", DbType="NVarChar(255)")]
        
public string PhotoPath
        {
            get
            {
                
return this._PhotoPath;
            }
            set
            {
                
if ((this._PhotoPath != value))
                {
                    
this.OnPhotoPathChanging(value);
                    
this.SendPropertyChanging();
                    
this._PhotoPath = value;
                    
this.SendPropertyChanged("PhotoPath");
                    
this.OnPhotoPathChanged();
                }
            }
        }
        
        
public event PropertyChangingEventHandler PropertyChanging;
        
        
public event PropertyChangedEventHandler PropertyChanged;
        
        
protected virtual void SendPropertyChanging()
        {
            
if ((this.PropertyChanging != null))
            {
                
this.PropertyChanging(this, emptyChangingEventArgs);
            }
        }
        
        
protected virtual void SendPropertyChanged(String propertyName)
        {
            
if ((this.PropertyChanged != null))
            {
                
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }
}
#pragma warning restore
1591

  

  从中可以看到,这里本质上就是以前的数据模型层,将数据整个对象化了,为了层之间的访问方便,我们将改类的命名空间改为Auto.DAL,并将NorthwindDataContent类的第一个构造函数代码修改如下,这样修改主要是为了统一数据库连接字符串的位置,因为dbml文件在生成后会附带生成一个app.config文件,用来存放连接字符串,而我们要把连接字符串统一放到web.config中。(要访问web.config文件,需要为DAL项目添加对System.Configuration的应用)

public NorthwindDataContext() :
        base(ConfigurationManager.ConnectionStrings[
"NorthwindConnectionString"].ConnectionString, mappingSource)
        {
            OnCreated();
        }

 

  

  完成前面的操作以后,开始建立数据访问层的类文件,这时,先在DAL项目下添加一个类文件,取名为DALEmployees.cs,其代码如下:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Auto.DAL
{
    
public class DALEmployees
    {
        
/// <summary>
        /// VS自动生成的数据模型
        /// </summary>
        NorthwindDataContext db = new NorthwindDataContext();
        
        
/// <summary>
        /// 根据条件获取数据列表方法
        /// </summary>
        /// <param name="strCity">城市地址</param>
        /// <returns>获取的Employees数据列表</returns>
        public IQueryable<Employees> GetList(string strCity)
        {
            
//根据城市地质,通过LINQ返回数据
            return from p in db.Employees
                      where p.City
== strCity
                      select p;
        }
    }
}

    这个数据访问层中只建立了一个用来根据城市地址获取Employee数据的方法,它内部执行一段LINQ,返回一个IQueryable型的结果,由于LINQ后期编译的特性,这个结果只有在程序运行后才会返回数据集。

  接着,建立业务逻辑层,在BLL项目中,添加一个类文件,取名为BLLEmployees.cs,其代码如下:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Auto.DAL;

namespace Auto.BLL
{
    
public class BLLEmployees
    {
        
/// <summary>
        /// 通过城市名获得Employee数据
        /// </summary>
        /// <param name="strCity">城市名</param>
        /// <returns>数据结果</returns>
        public IQueryable<Employees> GetList(string strCity)
        {
            DALEmployees de
=new DALEmployees();
            
//调用数据访问层的方法
            return de.GetList(strCity);
        }
    }
}

 

    这段代码完成了业务逻辑层的定义,建立了一个和数据访问层的同名方法GetList,用来传送城市名称参数。最后,在WEB Application项目中,添加对BLL层的应用,并在Default.aspx页面中添加一个GridView控件用来显示数据,Default.aspx.cs的代码如下:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using Auto.BLL;

namespace WebApplication2
{
    
public partial class _Default : System.Web.UI.Page
    {
        
protected void Page_Load(object sender, EventArgs e)
        {
            
if (!IsPostBack)
            {
                GetList(
"London");
            }
        }

        
/// <summary>
        /// 根据城市获取数据
        /// </summary>
        /// <param name="strCity">城市名称</param>
        private void GetList(string strCity)
        {
            
//执行业务逻辑层的方法
            BLLEmployees bl = new BLLEmployees();
            
//绑定到GridView1控件
            GridView1.DataSource = bl.GetList(strCity);
            GridView1.DataBind();
        }
    }
}

    完成后,执行程序,便可得到相关数据,整个程序的结构如下:

  总结:实际上,这个基于LINQ的架构是将数据模型层和数据访问层整合到一个项目中,它的特点就是开发快速,效率高,可以很方便的帮你完成数据模型的搭建,并且也便于后期修改,当数据表发生变动时,只选要修改dbml文件就可以了。但这个架构里有些地方还是不大完善,例如城市数据作为参数,应该也是以数据模型的方式来传送,但这里仅是按字符串传递,这样不利于数据的封装和安全。因此还需要在此处改进。总体来说,比以往的三层架构结构更加清晰了,如果再结合ASP.NET MVC架构来使用,就更加完美了。

0
相关文章