如果想在一個(gè)項(xiàng)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(gè)類，實(shí)現(xiàn)兩個(gè)子類：MySqlDapperPlus，MsSqlDapperPls，在這兩個(gè)子類的構(gòu)造中適配對(duì)應(yīng)的數(shù)據(jù)庫類型，從注放容器中，獲取IDbConnection實(shí)例，根據(jù)實(shí)例的類型來選取配置中的對(duì)應(yīng)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(shí)，會(huì)有問題，DapperPlus沒有無參構(gòu)造，_connection訪問級(jí)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(gòu)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"}

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如果是多個(gè)庫，還要讀寫分離該怎么實(shí)現(xiàn)？其實(shí)和不分離是一樣的，要改造《讓Dapper讀寫分離》中的DapperPlusWrite和DapperPlusRead兩個(gè)類，分別增加無參構(gòu)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(gè)類：MySqlDapperPlusRead和MsSqlDapperPlusRead繼承DapperPlusRead；MySqlDapperPlusWrite和MsSqlDapperPlusWrite繼承DapperPlusWrite。在四個(gè)類的構(gòu)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(wù)的Service中，讀有兩個(gè)，按類型區(qū)分，寫有兩個(gè)，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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