Question

我一直在玩一些用于n层数据访问的新模式，并且遇到了一个看起来非常灵活且易于实现的模式。基本上，我需要一个可以使各种数据层可以即时插拔/交换的解决方案 - 即从DB进行基本数据访问，分布式缓存，本地缓存等。

下面的代码很容易重复使用且非常高效 - 只比我之前完全硬编码的解决方案长几个小时。

这看起来怎么样？有没有什么办法可以更好地实施？任何一般的想法或批评？那些使用类似模式的人的任何输入？

基类：

public class DataAdapterFactory<T> where T : class
{
    private DataAdapter<T> Adapter;
    public DataAdapterFactory(DataAdapterBase<T> Base)
    {
        Adapter = Base;
    }
    public void Extend<U>() where U : DataAdapterExtender<T>, T, new()
    {
        DataAdapterExtender<T> Extender = new U();
        Extender.BaseAdapter = Adapter as T;
        Adapter = Extender;
    }
    public T GetAdapter()
    {
        return Adapter as T;
    }
}
public class DataAdapter<T> where T : class { }
public class DataAdapterBase<T> : DataAdapter<T> where T : class { }
public class DataAdapterExtender<T> : DataAdapter<T> where T : class
{
    public T BaseAdapter;
}

在DAL中实施：

// base interface defines methods
public interface IMyDataAdapter
{
    string GetString();
}
// base sql adapter
public class SqlDataAdapter : DataAdapterBase<IMyDataAdapter>, IMyDataAdapter
{
    public string GetString()
    {
        return "SQL";
    }      
}
// provides cache support
public class DistributedCacheExtender : DataAdapterExtender<IMyDataAdapter>, IMyDataAdapter
{
    public string GetString()
    {
        return BaseAdapter.GetString() + ", Distributed Cache";
    }   
}
// provides local cache support
public class LocalCacheExtender : DataAdapterExtender<IMyDataAdapter>, IMyDataAdapter
{
    public string GetString()
    {
        return BaseAdapter.GetString() + ", Local Cache";
    }
}

访问数据

public IMyDataAdapter GetAdapter() 
{
    // create adapter based on SqlDataAdapter
    DataAdapterFactory<IMyDataAdapter> factory = new DataAdapterFactory<IMyDataAdapter>(new SqlDataAdapter());
    // implement distributed cache
    factory.Extend<DistributedCacheExtender>();
    // implement local cache
    factory.Extend<LocalCacheExtender>();
    return factory.GetAdapter();
}

使用上面的工厂，基本适配器和扩展器的任何组合（必须按执行顺序调用Extend＆lt;＆gt;（））可以通过接口轻松无缝地使用，业务层一无所知实施。

在上面的这种情况下，调用GetString（）将导致“SQL，分布式缓存，本地缓存”。在现实世界中，首先调用本地缓存。如果没有项目，我们将转到分布式缓存，如果不存在，我们将从数据库中获取 - 并且根据需要可以根据需要交换任何模块。，用户等

Answer 1

我会看一下http://en.wikipedia.org/wiki/Decorator_pattern - 你的例子会变成这样：

public interface IMyDataAdapter
{
    string GetString();
}

public class SqlDataAdapter :  IMyDataAdapter
{
    public string GetString()
    {
        return "SQL";
    }      
}

public class LocalCacheDecorator : IMyDataAdapter
{
    private IMyDataAdapter adapter;
    public LocalCacheDecorator(IMyDataAdapter adapter)
    {
        this.adapter = adapter;
    }

    public string GetString()
    {
        return "Local cache, " + this.adapter.GetString();
    }
}

Answer 2

你正在做的事情看起来相当合理，尽管看看这些类如何与它们所在的命名空间和组合相关是有帮助的。

我的经验是抽象出接口背后的数据提供者，数据提供者（有时是接口）生活在一个单独的程序集中（因此：1代表BL，1代表接口，1代表每个数据提供者））。

我定义了围绕业务概念的接口（比如IPageDataProvider，ICustomerDataProvider等）而不是数据源（即数据库表），并且在设计接口时要注意Interface Segeration Principle。

我通过工厂在运行时加载了所需的数据提供程序;这使用Activator.CreateInstance方法。工厂从配置中获取它的说明。

因此，当我想在业务逻辑中使用数据时，我会通过工厂（一行代码）创建所需接口实现的实例。

使用这种方法，没有提供者具有的基类，但显然如果你愿意，你可以在数据提供者中使用基类。

Answer 3

我提出了一种混合抽象工厂，它可以满足你的目的，它也隐藏了开发人员的连接细节。它提供了一组连接，在我们的例子中，我们每组需要4个。这四个将由“连接集”工厂返回，还有一个'自定义连接集工厂，您可以随时更改返回的连接。您使用代理来访问连接对象。然后我通过单例访问代理，这样我可以在我的应用程序加载事件或global.asmx中设置它，然后很容易交换你正在使用的连接。虽然你可以交换运行时。希望这会有所帮助。

这是专门为我的场景编写的，所以对你来说可能有点矫枉过正？

请注意，这适用于npgsql，您可以轻松将其更改为标准.data。客户端基类，或sqlclent类......

    Public MustInherit Class DBConnectionDetail
    'note this abstract class could be an interface if you didn't want these common methods

    Protected _conStrBldr As New Npgsql.NpgsqlConnectionStringBuilder
    Protected _connection As Npgsql.NpgsqlConnection

    Public Sub New()
        'Set the connection builder properties in the subclass
    End Sub

    Friend ReadOnly Property ConnectionStringBuilder() As Npgsql.NpgsqlConnectionStringBuilder
        Get
            Return _conStrBldr
        End Get
    End Property


    Friend Property Connection() As Npgsql.NpgsqlConnection
        Get
            Return _connection
        End Get
        Set(ByVal value As Npgsql.NpgsqlConnection)
            _connection = value
        End Set
    End Property

    ' Misc properties - information for programmers of higher layers
    Public MustOverride ReadOnly Property Description() As String
    Public MustOverride ReadOnly Property HostName() As String
    Public MustOverride ReadOnly Property IP() As String
    Public MustOverride ReadOnly Property Database() As String
End Class



 Public Class LocalArchiveConnectionDetails
    Inherits DBConnectionDetail


    Public Sub New()
        _conStrBldr.Host = "localhost"
        _conStrBldr.Port = 5432
        _conStrBldr.UserName = "usr"
        _conStrBldr.Password = "pwd"
        _conStrBldr.Database = "archive"
        '_conStrBldr.Pooling = True
        '_conStrBldr.MinPoolSize = 5
        '_conStrBldr.MaxPoolSize = 10
        '_conStrBldr.CommandTimeout = 1024
        '_conStrBldr.Timeout = 1024
        '_conStrBldr.ConnectionLifeTime = 2
    End Sub


    Public Overrides ReadOnly Property Description() As String
        Get
            Return "Local Connection to Database"
        End Get
    End Property

    Public Overrides ReadOnly Property Database() As String
        Get
            Return "archive"
        End Get
    End Property

    Public Overrides ReadOnly Property HostName() As String
        Get
            Return "local host"
        End Get
    End Property

    Public Overrides ReadOnly Property IP() As String
        Get
            Return "127.0.0.1"
        End Get
    End Property
End Class

Public Interface IConnectionFactory

    ReadOnly Property GetMasterConnection() As DBConnectionDetail
    ReadOnly Property GetWarehouseConnection() As DBConnectionDetail
    ReadOnly Property GetArchiveConnection() As DBConnectionDetail
    ReadOnly Property GetAuditConnection() As DBConnectionDetail


End Interface

    Public Class DBConnectionBuilder

    Friend Shared Function GetConnection(ByVal conStrBldr As DBConnectionDetail) As NpgsqlConnection
        Return New NpgsqlConnection(conStrBldr.ConnectionStringBuilder.ConnectionString)
    End Function

    'Friend Shared Function GetConnection(ByVal conStr As String) As NpgsqlConnection
    '    Return New NpgsqlConnection(conStr)
    'End Function

End Class

    Public Class LocalConnectionFactory
    Implements IConnectionFactory


    Public ReadOnly Property GetArchiveConnection() As DBConnectionDetail Implements IConnectionFactory.GetArchiveConnection
        Get
            Dim dbConnection As New LocalArchiveConnectionDetails
            dbConnection.Connection = DBConnectionBuilder.GetConnection(dbConnection)
            Return dbConnection
        End Get
    End Property

    Public ReadOnly Property GetMasterConnection() As DBConnectionDetail Implements IConnectionFactory.GetMasterConnection
        Get
            Dim dbConnection As New LocalMasterConnectionDetails
            dbConnection.Connection = DBConnectionBuilder.GetConnection(dbConnection)
            Return dbConnection
        End Get
    End Property

    Public ReadOnly Property GetWarehouseConnection() As DBConnectionDetail Implements IConnectionFactory.GetWarehouseConnection
        Get
            Dim dbConnection As New LocalWarehouseConnectionDetails
            dbConnection.Connection = DBConnectionBuilder.GetConnection(dbConnection)
            Return dbConnection
        End Get
    End Property

    Public ReadOnly Property GetAuditConnection() As DBConnectionDetail Implements IConnectionFactory.GetAuditConnection
        Get
            Dim dbConnection As New LocalAuditConnectionDetails
            dbConnection.Connection = DBConnectionBuilder.GetConnection(dbConnection)
            Return dbConnection
        End Get
    End Property
End Class

 ''' <summary>
''' The custom connection factory allows higher layers to decide which connection will be returned by the connection proxy
''' </summary>
''' <remarks></remarks>
Public Class CustomConnectionFactory
    Implements IConnectionFactory

    Private _archiveConnection As DBConnectionDetail
    Private _masterConnection As DBConnectionDetail
    Private _warehouseConnection As DBConnectionDetail
    Private _auditConnection As DBConnectionDetail

    Friend Sub New()

    End Sub

    Friend Sub New(ByVal masterConnection As DBConnectionDetail, ByVal archiveConnection As DBConnectionDetail, _
                   ByVal warehouseConnection As DBConnectionDetail, ByVal auditConnection As DBConnectionDetail)
        _masterConnection = masterConnection
        _archiveConnection = archiveConnection
        _warehouseConnection = archiveConnection
        _auditConnection = auditConnection
    End Sub

    Friend Sub SetMasterConnectionDetail(ByVal connectionDetail As DBConnectionDetail)
        _masterConnection = connectionDetail
    End Sub
    Friend Sub SetArchiveConnectionDetail(ByVal connectionDetail As DBConnectionDetail)
        _archiveConnection = connectionDetail
    End Sub
    Friend Sub SetWarehouseConnectionDetail(ByVal connectionDetail As DBConnectionDetail)
        _warehouseConnection = connectionDetail
    End Sub
    Friend Sub SetAuditConnectionDetail(ByVal connectionDetail As DBConnectionDetail)
        _auditConnection = connectionDetail
    End Sub

    Public ReadOnly Property GetArchiveConnection() As DBConnectionDetail Implements IConnectionFactory.GetArchiveConnection
        Get
            _archiveConnection.Connection = DBConnectionBuilder.GetConnection(_archiveConnection)
            Return _archiveConnection
        End Get
    End Property

    Public ReadOnly Property GetMasterConnection() As DBConnectionDetail Implements IConnectionFactory.GetMasterConnection
        Get
            _masterConnection.Connection = DBConnectionBuilder.GetConnection(_masterConnection)
            Return _masterConnection
        End Get
    End Property

    Public ReadOnly Property GetWarehouseConnection() As DBConnectionDetail Implements IConnectionFactory.GetWarehouseConnection
        Get
            _warehouseConnection.Connection = DBConnectionBuilder.GetConnection(_warehouseConnection)
            Return _warehouseConnection
        End Get
    End Property

    Public ReadOnly Property GetAuditConnection() As DBConnectionDetail Implements IConnectionFactory.GetAuditConnection
        Get
            _auditConnection.Connection = DBConnectionBuilder.GetConnection(_auditConnection)
            Return _auditConnection
        End Get
    End Property
End Class

 Public Class DBConnectionsProxy

    Private _ConnectionsFactory As IConnectionFactory
    Private _CurrentConnectionsFactory As IConnectionFactory

    Public Sub New(ByVal connectionFactory As IConnectionFactory)
        'check that a connection factory is provided otherwise nothing will work
        If connectionFactory Is Nothing Then
            Throw New NullReferenceException("You must provide a connection factory")
        Else
            _ConnectionsFactory = connectionFactory
            _CurrentConnectionsFactory = connectionFactory
        End If
    End Sub

    Friend Property ConnectionFactory() As IConnectionFactory
        Get
            Return _CurrentConnectionsFactory
        End Get
        Set(ByVal value As IConnectionFactory)
            _CurrentConnectionsFactory = value
        End Set
    End Property

    Public ReadOnly Property GetMasterConnection() As Npgsql.NpgsqlConnection
        Get
            Return _CurrentConnectionsFactory.GetMasterConnection.Connection
        End Get
    End Property

    Public ReadOnly Property GetArchiveConnection() As Npgsql.NpgsqlConnection
        Get
            Return _CurrentConnectionsFactory.GetArchiveConnection.Connection
        End Get
    End Property

    Public ReadOnly Property GetWarehouseConnection() As Npgsql.NpgsqlConnection
        Get
            Return _CurrentConnectionsFactory.GetWarehouseConnection.Connection
        End Get
    End Property

    Public ReadOnly Property GetAuditConnection() As Npgsql.NpgsqlConnection
        Get
            Return _CurrentConnectionsFactory.GetAuditConnection.Connection
        End Get
    End Property


    ''' <summary>
    ''' Reset current connection factory to original connection factory this proxy was instantiated with
    ''' </summary>
    ''' <remarks></remarks>
    Public Sub ResetConnection()
        _CurrentConnectionsFactory = _ConnectionsFactory
    End Sub

    ''' <summary>
    ''' Changes the master connection returned for the current connection factory
    ''' </summary>
    ''' <param name="connectionDetail">Connection information for master database</param>
    ''' <remarks></remarks>
    Public Sub SetMasterConnection(ByVal connectionDetail As DBConnectionDetail)
        Me.SetAllConnections(connectionDetail, _CurrentConnectionsFactory.GetArchiveConnection, _
                             _CurrentConnectionsFactory.GetWarehouseConnection, _CurrentConnectionsFactory.GetAuditConnection)
    End Sub

    ''' <summary>
    ''' Changes the archive connection returned for the current connection factory
    ''' </summary>
    ''' <param name="connectionDetail">Connection information for archive database</param>
    ''' <remarks></remarks>
    Public Sub SetArchiveConnection(ByVal connectionDetail As DBConnectionDetail)
        Me.SetAllConnections(_CurrentConnectionsFactory.GetMasterConnection, connectionDetail, _
                             _CurrentConnectionsFactory.GetWarehouseConnection, _CurrentConnectionsFactory.GetAuditConnection)
    End Sub

    ''' <summary>
    ''' Changes the warehouse connection returned for the current connection factory
    ''' </summary>
    ''' <param name="connectionDetail">Connection information for warehouse database</param>
    ''' <remarks></remarks>
    Public Sub SetWarehouseConnection(ByVal connectionDetail As DBConnectionDetail)
        Me.SetAllConnections(_CurrentConnectionsFactory.GetMasterConnection, _CurrentConnectionsFactory.GetArchiveConnection, _
                             connectionDetail, _CurrentConnectionsFactory.GetAuditConnection)
    End Sub

    ''' <summary>
    ''' Changes the audit connection returned for the current connection factory
    ''' </summary>
    ''' <param name="connectionDetail">Connection information for audit database</param>
    ''' <remarks></remarks>
    Public Sub SetAuditConnection(ByVal connectionDetail As DBConnectionDetail)
        Me.SetAllConnections(_CurrentConnectionsFactory.GetMasterConnection, _CurrentConnectionsFactory.GetArchiveConnection, _
                             _CurrentConnectionsFactory.GetWarehouseConnection, connectionDetail)
    End Sub


    ''' <summary>
    ''' Sets the current connection factory to a custom connection factory using the supplied connection
    ''' </summary>
    ''' <param name="masterConnectionDetail">Connection information for master database</param>
    ''' <param name="archiveConnectionDetail">Connection information for archive database</param>
    ''' <param name="warehouseConnectionDetail">Connection information for warehouse database</param>
    ''' <remarks></remarks>
    Public Sub SetAllConnections(ByVal masterConnectionDetail As DBConnectionDetail, _
                                 ByVal archiveConnectionDetail As DBConnectionDetail, _
                                 ByVal warehouseConnectionDetail As DBConnectionDetail, _
                                 ByVal auditConnectionDetail As DBConnectionDetail)

        Dim customConnFactory As New CustomConnectionFactory
        customConnFactory.SetMasterConnectionDetail(masterConnectionDetail)
        customConnFactory.SetArchiveConnectionDetail(archiveConnectionDetail)
        customConnFactory.SetWarehouseConnectionDetail(warehouseConnectionDetail)
        customConnFactory.SetAuditConnectionDetail(auditConnectionDetail)

        _CurrentConnectionsFactory = customConnFactory
    End Sub


End Class

通用的多层数据访问模式？

3 个答案: