讓Dapper在一個項目中支持多種庫
如果想在一個項目中，用DapperPlus支持多種數(shù)據(jù)庫該怎么做？
在《讓Dapper支持Mock》中我們定義了DapperPlus，可以基于這個類，實現(xiàn)兩個子類：MySqlDapperPlus，MsSqlDapperPls，在這兩個子類的構造中適配對應的數(shù)據(jù)庫類型，從注放容器中，獲取IDbConnection實例，根據(jù)實例的類型來選取配置中的對應連接字符串，這里用到的是根據(jù)數(shù)據(jù)類型來配置，也是一種約定。
MySqlDapperPlus.cs
using Microsoft.Extensions.Configuration;using System;using System.Collections.Generic;using System.Data;using System.Linq;namespace WebDemo01.Services{public class MySqlDapperPlus : DapperPlus{public MySqlDapperPlus(IEnumerable<IDbConnection> connections, IConfiguration configuration){var connectionStrings = configuration.GetSection("ConnectionStrings").Get<Dictionary<string, string>>();_connection = connections.FirstOrDefault(c => c.GetType().Name == "MySqlConnection");_connection.ConnectionString = connectionStrings.Where(s => s.Key.ToLower().Contains("mysql")).FirstOrDefault().Value;}}}
MsSqlDapperPlus.cs
using Microsoft.Extensions.Configuration;using System;using System.Collections.Generic;using System.Data;using System.Linq;namespace WebDemo01.Services{public class MsSqlDapperPlus : DapperPlus{public MsSqlDapperPlus(IEnumerable<IDbConnection> connections, IConfiguration configuration){var connectionStrings = configuration.GetSection("ConnectionStrings").Get<Dictionary<string, string>>();_connection = connections.FirstOrDefault(c => c.GetType().Name == "SqlConnection");_connection.ConnectionString = connectionStrings.Where(s => s.Key.ToLower().Contains("mssql")).FirstOrDefault().Value;}}}
這時，會有問題，DapperPlus沒有無參構造，_connection訪問級別也太低，所以要改造一下DapperPlus。
/// <summary>/// DappePlusr類/// </summary>public class DapperPlus : IDapperPlus{protected IDbConnection _connection;/// <summary>/// 無參構造函數(shù)/// </summary>public DapperPlus(){}//下面和原來的一樣}
public void ConfigureServices(IServiceCollection services){services.AddControllers();services.AddScoped<IDbConnection, MySqlConnection>();services.AddScoped<IDbConnection, SqlConnection>();services.AddScoped<IDapperPlus, MySqlDapperPlus>();services.AddScoped<IDapperPlus, MsSqlDapperPlus>();}
appsettings.json
"ConnectionStrings": {"MySqlConnectionString": "server=127.0.0.1;uid=root;pwd=root;database=mysql_testdb","MsSqlConnectionString": "server=127.0.0.1;uid=root;pwd=root;database=mssql_testdb"}
如果是多個庫，還要讀寫分離該怎么實現(xiàn)？其實和不分離是一樣的，要改造《讓Dapper讀寫分離》中的DapperPlusWrite和DapperPlusRead兩個類，分別增加無參構造函數(shù)，和把_connection改成protected，方便子類中參訪問到。
然后定義三個類：MySqlDapperPlusRead和MsSqlDapperPlusRead繼承DapperPlusRead；MySqlDapperPlusWrite和MsSqlDapperPlusWrite繼承DapperPlusWrite。在四個類的構造函數(shù)中，按照自己數(shù)據(jù)庫的類型，Read或Write類型來取配置文件中的連接字符串即可。
Startup.cs
public void ConfigureServices(IServiceCollection services){services.AddControllers();services.AddScoped<IDbConnection, MySqlConnection>();services.AddScoped<IDbConnection, SqlConnection>();services.AddScoped<IDapperPlusRead, MySqlDapperPlusRead>();services.AddScoped<IDapperPlusRead, MsSqlDapperPlusRead>();services.AddScoped<IDapperPlusWrite, MySqlDapperPlusWrite>();services.AddScoped<IDapperPlusWrite, MsSqlDapperPlusWrite>();}
appsettings.json
"ConnectionStrings": {"MySqlReadConnectionString": "server=127.0.0.1;uid=root;pwd=root;database=read_mysql_testdb","MySqlWriteConnectionString": "server=127.0.0.1;uid=root;pwd=root;database=write_mysql_testdb","MsSqlReadConnectionString": "server=127.0.0.1;uid=root;pwd=root;database=read_mssql_testdb","MsSqlWriteConnectionString": "server=127.0.0.1;uid=root;pwd=root;database=write_mssql_testdb"}
最后，在業(yè)務的Service中，讀有兩個，按類型區(qū)分，寫有兩個，按類型區(qū)分，代碼如下：
public class GoodsService : IGoodsService{private readonly IDapperPlusWrite _mySqlDapperWrite;private readonly IDapperPlusWrite _msSqlDapperWrite;private readonly IDapperPlusRead _mySqlDapperRead;private readonly IDapperPlusRead _msSqlDapperRead;public ShopService(IEnumerable<IDapperPlusWrite> dapperWrites, IEnumerable<IDapperPlusRead> dapperReads){foreach (var dapperWrite in dapperWrites){switch (dapperWrite){case MySqlDapperPlusWrite mySqlDapperPlusWrite:_mySqlDapperWrite = mySqlDapperPlusWrite;break;case MsSqlDapperPlusWrite msSqlDapperPlusWrite:_msSqlDapperWrite = msSqlDapperPlusWrite;break;}}foreach (var dapperRead in dapperReads){switch (dapperRead){case MySqlDapperPlusRead mySqlDapperPlusRead:_mySqlDapperRead = mySqlDapperPlusRead;break;case MsSqlDapperPlusRead msSqlDapperPlusRead:_msSqlDapperRead = msSqlDapperPlusRead;break;}}}}
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