抽象工厂模式：实现ASP.NET访问不同数据库

来源：互联网发布：oracle恢复删除的数据编辑：程序博客网时间：2024/04/30 10:01

在ASP.NET网站开发中可能会遇到要更换数据库，如将Aceess换为SQL Server ，由于Aceess引用System.Data.OleDb命名空间，SQL Server引用System.Data.SqlClient命名空间。在一般程序代码中我们需要更改连接字符串，ADO.NET数据访问命令对象，最麻烦的是不同数据库有各自不同Sql命令。我们可以使用抽象工厂模式实现ASP.NET访问不同数据库。

1、抽象工厂模式（Abstract Factory）：提供一个创建一系列相互依赖对象的接口，而无需指定他们的具体类。

2、一般组成：抽象产品接口，具体产品类，抽象工厂接口，具体工厂类，客户端代码

3、作用：易于交换产品系列，在一个应用中只需在初始化的时候出现一次，这就使得改变一个应用的具体工厂的具体工厂变得非常容易，只需改变具体工厂即可使用不同的产品配置

让具体的创建实例过程与客户端分离，客户端是通过他们的抽象类接口操纵实例，产品的具体类名也被具体工厂是实现分离，不会出现在客户代码中。

网上提供的代码基本是为了讲解说明C#设计模式，由C#控制台程序代码实现，并没有真正实现访问数据库。我这里通过建立一个ASP.NET网站，实现访问Access与SQL Server数据库。主要参考《大话设计模式》

具体步骤代码如下：

1、分别在Access和SQL Server建立数据库DaHua与数据库表User(ID,Name)，Department（ID,DepartName）

2、启动Visual Studio 2005/2008新建网站

3、到web.config添加数据库连接

4、在网站解决方案右键新建类库ClassLibrary1，新建类文件，包括：

AbstractUser抽象类，SqlserverUser类，AccessUser类

AbstractDepartment抽象类，SqlserverDepartment类，AccessDepartment 类

DataAccess类

生成dll

5、到项目添加引用，项目-右键-添加引用-项目-ClassLibrary1

6、前台代码：添加一个GridView控件，三个Button控件，2个TextBox控件

用于查询表User和Department表内容，插入User表数据

using System;

using System.Configuration;

using System.Data;

using System.Linq;

using System.Web;

using System.Xml.Linq;

using System.Data.SqlClient;

using System.Data.OleDb;

using System.Reflection;

namespace ClassLibrary1

{

/// <summary>

///AbstractUser抽象类

/// </summary>

public abstract class AbstractUser

{

public abstract DataSet GetUser();

public abstract void InsertUser(string userID, string userName);

}

/// <summary>

/// SqlserverUser类

/// </summary>

public class SqlserverUser : AbstractUser

{

string constr = ConfigurationManager.ConnectionStrings["constrSQLDahua"].ConnectionString;

public override DataSet GetUser()

{

SqlConnection conn = new SqlConnection(constr);

if (conn.State == ConnectionState.Closed)

conn.Open();

SqlCommand cmd = new SqlCommand("select * from [User]", conn);

SqlDataAdapter sda = new SqlDataAdapter();

sda.SelectCommand = cmd;

DataSet ds = new DataSet();

sda.Fill(ds);

return ds;

}

public override void InsertUser(string userID, string userName)

{

SqlConnection conn = new SqlConnection(constr);

if (conn.State == ConnectionState.Closed)

conn.Open();

SqlCommand cmd = new SqlCommand();

cmd.Connection = conn;

cmd.CommandText = "insert into [User] values('" + Int32.Parse(userID) + "','" + userName + "') ";

cmd.ExecuteNonQuery();

conn.Close();

}

/// <summary>

/// AccessUser类

/// </summary>

public class AccessUser : AbstractUser

{

string constr = ConfigurationManager.ConnectionStrings["constrAccessDaHua"].ConnectionString;

public override DataSet GetUser()

{

OleDbConnection conn = new OleDbConnection(constr);

if (conn.State == ConnectionState.Closed)

conn.Open();

OleDbCommand cmd = new OleDbCommand("select * from [User]", conn);

OleDbDataAdapter sda = new OleDbDataAdapter();

sda.SelectCommand = cmd;

DataSet ds = new DataSet();

sda.Fill(ds);

return ds;

}

public override void InsertUser(string userID, string userName)

{

OleDbConnection conn = new OleDbConnection(constr);

if (conn.State == ConnectionState.Closed)

conn.Open();

OleDbCommand cmd = new OleDbCommand();

cmd.Connection = conn;

cmd.CommandText = "insert into [User] values('" + Int32.Parse(userID) + "','" + userName + "') ";

cmd.ExecuteNonQuery();

conn.Close();

}

/// <summary>

///AbstractDepartment抽象类

/// </summary>

public abstract class AbstractDepartment

{

public abstract DataSet GetDepartment();

// void InsertDepartment(string depID, string depName);

}

/// <summary>

/// SqlserverDepartment类

/// </summary>

public class SqlserverDepartment : AbstractDepartment

{

string constr = ConfigurationManager.ConnectionStrings["constrSQLDahua"].ConnectionString;

public override DataSet GetDepartment()

{

SqlConnection conn = new SqlConnection(constr);

if (conn.State == ConnectionState.Closed)

conn.Open();

SqlCommand cmd = new SqlCommand("select * from [Department]", conn);

SqlDataAdapter sda = new SqlDataAdapter();

sda.SelectCommand = cmd;

DataSet ds = new DataSet();

sda.Fill(ds);

return ds;

}

/// <summary>

/// AccessDepartment 类

/// </summary>

public class AccessDepartment : AbstractDepartment

{

string constr = ConfigurationManager.ConnectionStrings["constrAccessDaHua"].ConnectionString;

public override DataSet GetDepartment()

{

OleDbConnection conn = new OleDbConnection(constr);

if (conn.State == ConnectionState.Closed)

conn.Open();

OleDbCommand cmd = new OleDbCommand("select * from [Department]", conn);

OleDbDataAdapter sda = new OleDbDataAdapter();

sda.SelectCommand = cmd;

DataSet ds = new DataSet();

sda.Fill(ds);

return ds;

}

/// <summary>

///DataAccess类

///使用反射

/// </summary>

public class DataAccess

{

private static readonly string AssemblyName = "ClassLibrary1"; //程序集名称

private static readonly string db = "Sqlserver"; //数据库类型名，要更改访问的数据库，只需更改这里

public static AbstractUser CreateUser()

{

string className = AssemblyName + "." + db + "User"; //命名空间.要实例化的类名

return (AbstractUser)Assembly.Load(AssemblyName).CreateInstance(className);

}

public static AbstractDepartment CreateDepartment()

{

string className = AssemblyName + "." + db + "Department";

return (AbstractDepartment)Assembly.Load(AssemblyName).CreateInstance(className);

}

前台代码：

public partial class _Default : System.Web.UI.Page

{

ClassLibrary1.AbstractUser au = null;

ClassLibrary1.AbstractDepartment ad = null;

protected void Page_Load(object sender, EventArgs e)

{

}

protected void Button1_Click(object sender, EventArgs e)

{

au =ClassLibrary1.DataAccess.CreateUser();

DataSet ds = au.GetUser();

GridView1.DataSource = ds;

GridView1.DataBind();

}

protected void Button2_Click(object sender, EventArgs e)

{

string userID = txtID.Text;

string userName = txtName.Text ;

au = ClassLibrary1.DataAccess.CreateUser();

au.InsertUser(userID,userName);

}

//部门查询

protected void Button3_Click(object sender, EventArgs e)

{

ad = ClassLibrary1.DataAccess.CreateDepartment();

DataSet ds = ad.GetDepartment();

GridView1.DataSource = ds;

GridView1.DataBind();

}