经常在网上看到对ORM的讨论沸沸扬扬，我也来凑个热闹，谈谈我写的一个ORM。最近在做一项工作，把我们经常用到的一些业务逻辑抽象出来，写成一个个的Application Block，使之可以运用到不同的Application中，比如Data Access，Messaging，Auditing，Data binding等等。现在先做一个Data access application block。由于时间仓促，没有进行什么优化和较多的测试，大家不必深究我所提供的Code ,我只希望为大家的ORM提供另一种想法。
这个application block应达到的目的：
-
封装所有的Data Access操作。
-
适合主流的DBMS：SQL Server（2000和2005），Oracle（9i和10g），DB2。
-
尽量简化Developer的操作和提供最大的灵活性，在Data Retrieval方面，只要指定SQL或者Stored Procedure和相应的参数；在Data Update方面，既可以直接调用SQL和Stored Procedure，还可以把包含多个相互关联Data Table的Dataset通过一次调用实现数据的更新。此外，可以自由地选择使用SQL还是Stored procedure；可以使用Commander builder生成Command或者使用基于Mapped stored procedure生成的Command进行数据更新。
-
实现泛型编程，使使用该AppBlock的代码能够适合所有的数据库。
-
实现Transaction。
-
提供可配置性，包括不同数据库的配置，不同Data Mapping的配置等等。
下面是该AppBlock使用到的Entity:
![开发自己的Data Access Application Block[上篇]_第1张图片](http://img.e-com-net.com/image/info8/ca0b6dac43194ae0b5c3f182636c0288.jpg)
-
Database：Abstract Class，封装了绝大部分和具体数据库无关的Data Access操作逻辑。通过两个Mapping：IDbParameterNameMapping和IStoredProcedureNameMapping，实现Dataset和Db的一个映射。比如Dataset中Data table name和Stored procedure name的Mapping，Data table中Field和Stored procedure中参数名的Mapping。这两个Mapping是可以配置的，你只需要实现提供的Interface编写适合你的Mapping provider就可以了。
-
SqlDatabase：封装基于SQL Server 的操作。ADO.NET 2.0在1.0的基础上作了很大的改善，主要的增加的大量的基类，为我们进行泛型编程，编写和具体Db无关的代码变得异常容易。所以我们把大多数Data Access的操作可以封装在Abstract Database类中，SqlDatabase中的内容实际上是很少的。
-
OracleDatabase：封装基于Oracle的操作。
-
IDbParameterNameMapping和IStoredProcedureNameMapping：我想大家都是这样的感受，实现ORM的本质就是实现内存中的数据（主要是Dataset）和数据库的一个映射。在Dataset和数据库中的Table相互Mapping方面，我觉得没有必要采用特殊的Mapping，直接和简单易行的就是Table和Dataset中的Data Table完全匹配（table name 和field name完全匹配）。所以重要的是实现Dataset和Stored procedure的Mapping：Table Name如何与进行Insert，Update，Delete的Stored procedure name匹配，不同Version（original & current）的Field如何与Stored procedure的Parameter name 匹配。而这样一个匹配应该是可配置的，因为每个Application在数据库设计时的命名都有各自的要求，所以我在这里采用的Provider的设计模式。用户可以实现这两个Interface编写适合自己的Mapping provider，通过我提供的Configuration block很容易地完成配置。同时，我写了一个默认的，简单的Mapping：SimpleDbParameterNameMapping和SimpleStoredProcedureNameMapping。
有一点需要补充的是，要实现上面的Mapping，对Stored Procedure的命名有较高的要求，手工编写的方式已经不能适合我们的要求，所以我们需要一个生成Stored procedure的Generator，这个Generator也使用这两个可配置的Mapping接口。
为了使大家清楚地看出这个Application block所有的操作，我把所有的操作封装在一个IDatabase的interface中，不过需要注意的是，我采用的是基于Abstract class的编程，而不是基于Interface的编程，相信大家对这两种方式讨论得已经碰倒的太多了，孰优孰劣我就不想对说了。这个IDatabase 接口，只是展示所有Operation之用，并没有在我的代码中用到。
namespace Artech.ApplicationBlock.DataAccess
{
public interface IDatabase
{
Fill a System.Data.DataSet with retrieved data.#region Fill a System.Data.DataSet with retrieved data.
void FillDataSet(DataSet dataInfo, string commandText, IDictionary<string, object> parameters);
void FillDataSet(DataSet dataInfo, string tableName, string commandText, IDictionary<string, object> parameters);
void FillDataSet(DataSet dataInfo, string tableName, CommandType commandType, string commandText, IDictionary<string, object> parameters);
#endregion
Save the changed data which is stored in a dataset into database.#region Save the changed data which is stored in a dataset into database.
void UpdateData(DataSet dataInfo);
void UpdateData(DataTable table);
void UpdateData(DataTable table, string insertCommandText, string updateCommandText, string deleteCommandText,
Dictionary<string, object> insertParameters, Dictionary<string, object> updateParameters, Dictionary<string, object> deleteParameters);
void UpdateData(DataTable table, CommandType commandType, string insertCommandText, string updateCommandText, string deleteCommandText,
Dictionary<string, object> insertParameters, Dictionary<string, object> updateParameters, Dictionary<string, object> deleteParameters);
void UpdateData(DataTable table, DbCommand insertCommand, DbCommand updateCommand, DbCommand deleteCommand);
#endregion
Execute a command and return the affect row count.#region Execute a command and return the affect row count.
int ExecuteNonQuery(CommandType commandType, string commandText, Dictionary<string, object> inputParameters, Dictionary<string, object> outputParameters);
int ExecuteNonQuery(CommandType commandType, string commandText, Dictionary<string, object> inputParameters);
int ExecuteNonQuery( string commandText, Dictionary<string, object> inputParameters, Dictionary<string, object> outputParameters);
int ExecuteNonQuery( string commandText, Dictionary<string, object> inputParameters);
#endregion
Execute a command and return the data in the form of data reader.#region Execute a command and return the data in the form of data reader.
DbDataReader ExecuteReader(CommandType commandType, string commandText, Dictionary<string, object> inputParameters, Dictionary<string, object> outputParameters);
DbDataReader ExecuteReader(CommandType commandType, string commandText, Dictionary<string, object> inputParameters);
DbDataReader ExecuteReader(string commandText, Dictionary<string, object> inputParameters, Dictionary<string, object> outputParameters);
DbDataReader ExecuteReader(string commandText, Dictionary<string, object> inputParameters);
#endregion
Execute a command and return a scalar value.#region Execute a command and return a scalar value.
object ExecuteScalar(CommandType commandType, string commandText, Dictionary<string, object> inputParameters, Dictionary<string, object> outputParameters);
object ExecuteScalar(CommandType commandType, string commandText, Dictionary<string, object> inputParameters);
object ExecuteScalar(string commandText, Dictionary<string, object> inputParameters, Dictionary<string, object> outputParameters);
object ExecuteScalar(string commandText, Dictionary<string, object> inputParameters);
#endregion
Transaction based operation#region Transaction based operation
void BeginTransaction();
void Commit();
void RollBack();
#endregion
}
}
这个列表和大部分ORM没有什么太大的区别，大家已经司空见惯，实现起来也不会有什么太大的困难。对于大部分操作，我不会做详细的介绍。接下来我们来简要地看看这样一个AppBlock是如何实现的。
1. Data Mapping
我们首先来看看Data Mapping：实现Dataset中Table name和Stored Procedure Name的Mapping，以及Dataset 中的Field 和Stored procedure的参Parameter name的Mapping。
IDbParameterNameMapping
using System;
using System.Collections.Generic;
using System.Text;
namespace Artech.ApplicationBlock.DataMapping
{
/**////
/// IStoredProcedureNameMapping defines the mapping between the data table name and the name of stored procedures to perform insertion, modification and deletion operation.
///
public interface IStoredProcedureNameMapping
{
/**////
/// Get the name of stored procedure to perform seletion operation.
///
/// The name of the database table.
/// The name of stored procedure to perform seletion operation
string GetSelectStoredProcedureName(string tableName);
/**////
/// Get the name of stored procedure to perform insert operation.
///
/// The name of the database table.
/// The name of stored procedure to perform insertion operation
string GetInsertStoredProcedureName(string tableName);
/**////
/// Get the name of stored procedure to perform modification operation.
///
/// The name of the database table.
/// The name of stored procedure to perform modification operation
string GetModifyStoredProcedureName(string tableName);
/**////
/// Get the name of stored procedure to perform deletion operation.
///
/// The name of the database table.
/// The name of stored procedure to perform deletion operation
string GetDeleteStoredProcedureName(string tableName);
}
}
IDbParameterNameMapping
using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
namespace Artech.ApplicationBlock.DataMapping
{
/**////
/// IDbParameterNameMapping define the defult mapping between the source column name and the parameter name of the corresponding stored procedure.
///
public interface IDbParameterNameMapping
{
/**////
/// Get the source column name based on the parameter name of the related stored procedure.
///
/// The parameter name of the corresponding stored procedure.
/// The source column name corresponding to the parameter name.
string GetSourceCoulmnName(string patameterName);
/**////
/// Get the source parameter name based on the source column name.
///
/// The source column name corresponding to the parameter name.
/// The data row version of the source solumn conressponding to the parameter.
/// The parameter name of the corresponding stored procedure.
string GetParameterName(string columnName, DataRowVersion rowVersion);
}
}
这两个Mapping主要用在通过Dataset跟新数据库的场景，利用IDbParameterNameMapping，我们通过Dataset中各个Table name获得对它进行Insert，Update，Delete操作的Stored procedure的name。利用IDbParameterNameMapping，我们可以为Stored procedure的Parameter指定对应的Source field.
注：GetParameterName方法实际上是不需要的，我把使用在另一个AppBlock中。
接下来我们来写两个实现了上面连个Interface的默认的mapping：SimpleStoredProcedureNameMapping和SimpleDbParameterNameMapping。他实际上实现了这样的Mapping：比如Table name为T_ABC_DEF（我经常用的命名方式：以T开头代表Table，名称大写并一下划线连接），那么对应的Stored procedure name分别为：sp_abc_def_s（Select）, sp_abc_def_i(Insert), sp_abc_def_u(Update), sp_abc_def_d(delete)。如果Field name为ABC_123,那么对于Original version的Parameter name为o_abc_123(o代表Original)，Current version的Parameter name为p_abc_123（p代表一般意义的Parameter）。
using System;
using System.Collections.Generic;
using System.Text;
namespace Artech.ApplicationBlock.DataMapping
{
/**////
/// IStoredProcedureNameMapping defines the mapping between the data table name and the name of stored procedures to perform insertion, modification and deletion operation.
///
public class SimpleStoredProcedureNameMapping:IStoredProcedureNameMapping
{
IStoredProcedureNameMapping Members#region IStoredProcedureNameMapping Members
/**////
/// Get the name of stored procedure to perform selection operation.
///
/// The name of the database table.
/// The name of stored procedure to perform selection operation
public string GetSelectStoredProcedureName(string tableName)
{
//T_ABC_DEF=>sp_abc_def_s
return string.Format("sp_{0}_s", tableName.Substring(2, tableName.Length - 2).ToLower());
}
/**////
/// Get the name of stored procedure to perform insert operation.
///
/// The name of the database table.
/// The name of stored procedure to perform insertion operation
public string GetInsertStoredProcedureName(string tableName)
{
//T_ABC_DEF=>sp_abc_def_i
return string.Format("sp_{0}_i", tableName.Substring(2, tableName.Length - 2).ToLower());
}
/**////
/// Get the name of stored procedure to perform modification operation.
///
/// The name of the database table.
/// The name of stored procedure to perform modification operation
public string GetModifyStoredProcedureName(string tableName)
{
//T_ABC_DEF=>sp_abc_def_u
return string.Format("sp_{0}_u", tableName.Substring(2, tableName.Length - 2).ToLower());
}
/**////
/// Get the name of stored procedure to perform deletion operation.
///
/// The name of the database table.
/// The name of stored procedure to perform deletion operation
public string GetDeleteStoredProcedureName(string tableName)
{
//T_ABC_DEF=>sp_abc_def_d
return string.Format("sp_{0}_d", tableName.Substring(2, tableName.Length - 2).ToLower());
}
#endregion
}
}
SimpleDbParameterNameMapping
using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
namespace Artech.ApplicationBlock.DataMapping
{
/**////
/// SimpleDbParameterNameMapping defines a simple mapping method between the corresponding parameter name and source culumn name of the table.
///
public class SimpleDbParameterNameMapping:IDbParameterNameMapping
{
IDbParameterNameMapping Members#region IDbParameterNameMapping Members
/**////
/// Get the source column name based on the parameter name of the related stored procedure.
///
/// The parameter name of the corresponding stored procedure.
/// The source column name corresponding to the parameter name.
public string GetSourceCoulmnName(string patameterName)
{
//@p_abc_def|o_abc_def=>ABC_DEF
return patameterName.Substring(3, patameterName.Length - 3).ToUpper();
}
/**////
/// Get the source parameter name based on the source column name.
///
/// The source column name corresponding to the parameter name.
/// The data row version of the source solumn conressponding to the parameter.
/// The parameter name of the corresponding stored procedure.
public string GetParameterName(string columnName, DataRowVersion rowVersion)
{
//ABC_DEF =>@p_abc_def|o_abc_def
string prefix = "@p";
if (rowVersion == DataRowVersion.Original)
{
prefix = "@o";
}
return string.Format("{0}_{1}", prefix, columnName.ToLowerInvariant());
}
#endregion
}
}
2. Configuration
对于一个能够被不同Application使用的Application Block，可配置性是最基本的要求，为此，我为整个AppBlock编写了单独的Configuration。在很多情况下我们在一个Application中会使用到多个具有相同或不同类型的数据库，所以这个Configuration System也许我们配置若干数据库。因而我充分利于了ConfigurationElementCollection，ConfigurationElementCollection中的每个Element对应一个具体的数据库。相关的配置信息包括：
-
一个唯一标该识数据库的DatabaseName（配置名称为name）
-
一个带面Data access provider类型的DbProvider（配置名称为dbProvider）
-
每个Db对应的ConnectionString（配置名称为connectionString）
-
代表是否是Default Db的IsDefaultDatabase（配置名称为isDefault）
-
两个Mapping ：DbParameterNameMapping和StoredProcedureNameMapping（配置名称为dbParameterNameMapping和storedProcedureNameMapping，默认值为我丁一的默认Mapping type）
-
默认的Command Type：DedaultCommandType（配置名称为dedaultCommandType，默认为使用stored procedure）
-
使用CommandBuilder生成的Command还是使用Mapped stored procedure生成的Command进行Update：UsingCommandBuilderToUpdate（配置名称为usingCommandBuilderToUpdate，默认为使用Mapped stored procedure）。
ConfigurationElementCollection
using System;
using System.Collections.Generic;
using System.Text;
using System.Configuration;
namespace Artech.ApplicationBlock.Configuration
{
public class DataAccessConfigurationCollection: ConfigurationElementCollection
{
protected override ConfigurationElement CreateNewElement()
{
return new DataAccessConfigurationElement();
}
protected override object GetElementKey(ConfigurationElement element)
{
DataAccessConfigurationElement configurationElement = element as DataAccessConfigurationElement;
if (configurationElement == null)
{
throw new Exception("It is fail to parse the data access configuration");
}
return configurationElement.DatabaseName;
}
}
}
DataAccessConfigurationElement
using System;
using System.Collections.Generic;
using System.Text;
using System.Configuration;
using System.Data;
namespace Artech.ApplicationBlock.Configuration
{
public class DataAccessConfigurationElement:ConfigurationElement
{
/**////
/// The database namw which uniquely identifies the current database.
///
[ConfigurationProperty("name", IsRequired = true)]
public string DatabaseName
{
get
{
return this["name"] as string;
}
set
{
this["name"] = value;
}
}
/**////
/// A string indicating the concrete database provider.
///
[ConfigurationProperty("dbProvider", DefaultValue = "System.Data.SqlClient")]
public string DbProvider
{
get
{
return this["dbProvider"] as string;
}
set
{
this["dbProvider"] = value;
}
}
/**////
/// A string indicating the connection string to connect to the concrete database.
///
[ConfigurationProperty("connectionString")]
public string ConnectionString
{
get
{
return this["connectionString"] as string;
}
set
{
this["connectionString"] = value;
}
}
/**////
/// A flag which determines if this is the default database.
///
[ConfigurationProperty("isDefault", DefaultValue = false)]
public bool IsDefaultDatabase
{
get
{
return (bool)this["isDefault"];
}
set
{
this["isDefault"] = value;
}
}
/**////
/// A bool flag indicating if the default operation are all executed using command builder or stored procedure.
///
[ConfigurationProperty("usingCommandBuilderToUpdate", DefaultValue = false)]
public bool UsingCommandBuilderToUpdate
{
get
{
return (bool)this["usingCommandBuilderToUpdate"];
}
set
{
this["usingCommandBuilderToUpdate"] = value;
}
}
/**////
/// A CommandType enumeration indicating if the default command type.
///
[ConfigurationProperty("dedaultCommandType", DefaultValue = CommandType.StoredProcedure)]
public CommandType DedaultCommandType
{
get
{
return (CommandType)this["dedaultCommandType"];
}
set
{
this["dedaultCommandType"] = value;
}
}
/**////
/// A string indicating the type of the class to perform mapping between parameter and the source column name.
///
[ConfigurationProperty("dbParameterNameMapping", DefaultValue = "Artech.ApplicationBlock.DataMapping.SimpleDbParameterNameMapping,Artech.ApplicationBlock.DataMapping")]
public string DbParameterNameMapping
{
get
{
return this["dbParameterNameMapping"] as string;
}
set
{
this["dbParameterNameMapping"] = value;
}
}
/**////
/// A string indicating the type of the class to perform mapping between the data table name and the name of stored procedures to perform insertion, modification and deletion operation.
///
[ConfigurationProperty("storedProcedureNameMapping", DefaultValue = "Artech.ApplicationBlock.DataMapping.SimpleStoredProcedureNameMapping,Artech.ApplicationBlock.DataMapping")]
public string StoredProcedureNameMapping
{
get
{
return this["storedProcedureNameMapping"] as string;
}
set
{
this["storedProcedureNameMapping"] = value;
}
}
}
}
DataAccessConfigurationSection
using System;
using System.Collections.Generic;
using System.Text;
using System.Configuration;
using System.Data;
namespace Artech.ApplicationBlock.Configuration
{
public class DataAccessConfigurationSection: ConfigurationSection
{
[ConfigurationProperty("", IsDefaultCollection = true)]
public DataAccessConfigurationCollection Databases
{
get
{
return this[""] as DataAccessConfigurationCollection;
}
set
{
this[""] = value;
}
}
}
}
我们可以把我们定义的Configure通过下面的方式运用到configuration文件中。
xml version="1.0"
?>
<
configuration
>
<
configSections
>
<
sectionGroup
name
="Artech.ApplicationBlock"
type
="Artech.ApplicationBlock.Configuration.ApplicationBlockConfigurationSectionGroup, Artech.ApplicationBlock.Configuration"
>
<
section
name
="Artech.ApplicationBlock.DataAccess"
type
="Artech.ApplicationBlock.Configuration.DataAccessConfigurationSection,Artech.ApplicationBlock.Configuration"
/>
<
section
name
="Artech.ApplicationBlock.Messaging"
type
="Artech.ApplicationBlock.Configuration.MessagingConfigurationSection,Artech.ApplicationBlock.Configuration"
/>
sectionGroup
>
configSections
>
<
Artech
.ApplicationBlock
>
<
Artech
.ApplicationBlock.DataAccess
>
<
add
name
="sqlDatabase"
connectionString
="Data Source=JIANGJINNAN\SQLEXPRESS;Initial Catalog=iFramework;Integrated Security=True"
>
add
>
Artech.ApplicationBlock.DataAccess
>
Artech.ApplicationBlock
>
configuration
>
注：我把我开发的所有AppBlock相关的Configuration放在一个自定义的叫做ApplicationBlockConfigurationSectionGroup的ConfigurationSectionGroup中（），我推荐大家使用这种方式，一来可以使结构更加清晰，二来在你需要的时候，扩展该ConfigurationSectionGroup加入一些公用的配置。
3. Database Factory
为了实现泛型化的编程，使我的代码和具体的数据库无关，我采用了Factory的模式。我定义了两个重载的方法CreateDatabase，调用没有参数的方法创建一个默认的Database（isDefault=”true”）, 调用有参数的方法通过传入配置的Database的name创建我们需要的Database。具体的逻辑就是通过ConfigurationManager提取相应的Configuration 信息，通过DbProvider创建对应类型的Database (比如”System.Data.SqlClient”对应SQL Server)。把provider的信息传入System.Data.Common.DbProviderFactories.GetFactory方法创建一个System.Data.Common。DbProviderFactory赋值给创建的Database的DatabaseProviderFactory属性（DbProviderFactory是一个很有价值的Type，为我们创建一个泛型的ADO.NET对象提供了方便）。同时把其他的配置信息赋值给创建的Database相应的属性。提取两个Mapping Type的信息，通过Reflection的机制创建相应的类型，并同时把其他的配置信息赋值给创建的Database相应的属性。
using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
using System.Data.Common;
using System.Reflection;
using System.Configuration;
using Artech.ApplicationBlock.Configuration;
using Artech.ApplicationBlock.Common;
using Artech.ApplicationBlock.DataMapping;
using Artech.ApplicationBlock.Common.Exceptions;
namespace Artech.ApplicationBlock.DataAccess
{
public static class DatabaseFactory
{
static void ThrowAConfigurationException()
{
throw new CustomConfigurationException(CommonConstant.DataAccess.Messages.ConfigurationError);
}
static DatabaseFactory()
{
}
/**////
/// Create the default database.
///
/// Default database.
public static Database CreateDatabase()
{
DataAccessConfigurationElement configurationElement = ApplicationBlockConfiguration.GetDataAccessConfigurationElement();
Database database = null;
if (configurationElement.DbProvider == CommonConstant.DataAccess.ProviderInvariantName_SqlServer)
{
database = new SqlDatabase();
}
else
{
}
database.ConnectionString = configurationElement.ConnectionString;
database.DatabaseProviderFactory = DbProviderFactories.GetFactory(configurationElement.DbProvider);
database.DefaultCommandType = configurationElement.DedaultCommandType;
Type dbParameterNameMappingType = Type.GetType(configurationElement.DbParameterNameMapping);
database.DbParameterNameMapping = (IDbParameterNameMapping)dbParameterNameMappingType.GetConstructor(new Type[0]).Invoke(new object[0]);
Type storedProcedureNameMappingType = Type.GetType(configurationElement.StoredProcedureNameMapping);
database.StoredProcedureNameMapping = (IStoredProcedureNameMapping)storedProcedureNameMappingType.GetConstructor(new Type[0]).Invoke(new object[0]);
database.UseCommandBuilder = configurationElement.UsingCommandBuilderToUpdate;
return database;
}
/**////
/// Create a particular database by specifying the configurable database name.
///
/// the name of database specified in configuration.
/// The database corresponding to the database name.
public static Database CreateDatabase(string databaseName)
{
DataAccessConfigurationElement configurationElement = ApplicationBlockConfiguration.GetDataAccessConfigurationElement(databaseName);
Database database = null;
if (configurationElement.DbProvider == CommonConstant.DataAccess.ProviderInvariantName_SqlServer)
{
database = new SqlDatabase();
}
else
{
}
database.ConnectionString = configurationElement.ConnectionString;
database.DatabaseProviderFactory = DbProviderFactories.GetFactory(configurationElement.DbProvider);
database.DefaultCommandType = configurationElement.DedaultCommandType;
Type dbParameterNameMappingType = Type.GetType(configurationElement.DbParameterNameMapping);
database.DbParameterNameMapping = (IDbParameterNameMapping)dbParameterNameMappingType.GetConstructor(new Type[0]).Invoke(new object[0]);
Type storedProcedureNameMappingType = Type.GetType(configurationElement.StoredProcedureNameMapping);
database.StoredProcedureNameMapping = (IStoredProcedureNameMapping)storedProcedureNameMappingType.GetConstructor(new Type[0]).Invoke(new object[0]);
database.UseCommandBuilder = configurationElement.UsingCommandBuilderToUpdate;
return database;
}
}
}
注：上面的代码是不完整的，仅仅做到SQL Server的支持，由于基于Configuration的逻辑被我封装在另一个Configuration AppBlock中，所以代码中包含有对此的调用，相信不会影响大家的理解。
[原创]我的ORM: 开发自己的Data Access Application Block - Part II
