多数据库连接的一种注入方式

[hd2y]

参考 #44

如果针对数据库连接是以配置为主，并且在一个请求中需要同时操作多个数据库连接，MultiFreeSql 的实现就没有那么好用了。

针对此，可以参考以下代码：

public delegate IFreeSql FreeSqlResolver(string key);

public static class FreeSqlExtensions
{
    private static readonly Dictionary<string, IFreeSql> FreeSqlDictionary = new Dictionary<string, IFreeSql>();

    private static readonly object Locker = new object();

    public static IServiceCollection AddFreeSql(this IServiceCollection services, IConfiguration configuration)
    {
        services
            .Configure<Dictionary<string, FreeSqlOptions>>(configuration.GetSection("FreeSql"))
            .AddSingleton<FreeSqlResolver>(provider => key =>
            {
                lock (Locker)
                {
                    if (FreeSqlDictionary.TryGetValue(key, out var freeSql)) return freeSql;

                    var options = provider.GetRequiredService<IOptions<Dictionary<string, FreeSqlOptions>>>().Value;
                    if (!options.TryGetValue(key, out var value))
                        throw new KeyNotFoundException($"未添加{key}的FreeSql连接配置");

                    var logger = provider.GetRequiredService<ILogger<IFreeSql>>();

                    logger.LogInformation("连接数据库 {DataType}@{Flag}", value.DataType, key);

                    var db = new FreeSqlBuilder()
                        .UseConnectionString(value.DataType, value.ConnectionString)
                        .UseNoneCommandParameter(value.EnableNoneCommandParameter)
                        .UseAutoSyncStructure(value.EnableAutoSyncStructure)
                        .UseSlave(value.SlaveConnectionStrings)
                        .Build();

                    // 启用 JsonMap
                    if (value.EnableJsonMap)
                    {
                        db.UseJsonMap(new JsonSerializerSettings
                            { NullValueHandling = NullValueHandling.Ignore });
                    }

                    // 启用日志记录
                    if (value.EnableLogger)
                    {
                        db.Aop.CurdBefore += (_, e) =>
                        {
                            if (e.DbParms.IsNullOrEmpty())
                            {
                                logger.Log(value.LogLevel ?? LogLevel.Debug,
                                    "{Flag}数据库执行:\nSql: {Sql}",
                                    key, e.Sql);
                            }
                            else
                            {
                                logger.Log(value.LogLevel ?? LogLevel.Debug,
                                    "{Flag}数据库执行:\nSql: {Sql}\nDbParms: {@Parameter}",
                                    key, e.Sql, e.DbParms);
                            }

                            Debug.WriteLine(e.Sql);
                        };
                    }

                    FreeSqlDictionary.Add(key, db);

                    return db;
                }
            });

        return services;
    }

    /// <summary>
    /// 开启事务，回滚需要抛异常
    /// </summary>
    /// <param name="freeSql"></param>
    /// <param name="handle"></param>
    /// <typeparam name="T"></typeparam>
    /// <returns></returns>
    public static T Transaction<T>(this IFreeSql freeSql, Func<T> handle)
    {
        T result = default;
        freeSql.Transaction(() => result = handle.Invoke());
        return result;
    }

    public static IFreeSql Get(this FreeSqlResolver resolver, string key)
    {
        return resolver(key);
    }

    public static IFreeSql GetWms(this FreeSqlResolver resolver)
    {
        return resolver(Const.WmsDbKey);
    }

    public static IFreeSql GetInterface(this FreeSqlResolver resolver)
    {
        return resolver(Const.InterfaceDbKey);
    }
}

对应的有一个配置：

public class FreeSqlOptions
{
    public DataType DataType { get; set; }

    public string ConnectionString { get; set; }
    
    public bool EnableNoneCommandParameter { get; set; }
    
    public bool EnableAutoSyncStructure { get; set; }
    
    public string[] SlaveConnectionStrings { get; set; }
    
    public bool EnableJsonMap { get; set; }
    
    public bool EnableLogger { get; set; }
    
    public LogLevel? LogLevel { get; set; }
}

基于此我们可以进行配置：

{
  "FreeSql": {
    "Db1": {
      "ConnectionString": "",
      "DataType": "SqlServer",
      "SlaveConnectionStrings": null,
      "EnableNoneCommandParameter": true,
      "EnableAutoSyncStructure": false,
      "EnableJsonMap": false,
      "EnableLogger": true,
      "LogLevel": null
    },
    "Db2": {
      "ConnectionString": "",
      "DataType": "SqlServer",
      "SlaveConnectionStrings": null,
      "EnableNoneCommandParameter": true,
      "EnableAutoSyncStructure": true,
      "EnableJsonMap": true,
      "EnableLogger": true,
      "LogLevel": null
    }
  }
}

使用时首先需要先调用 AddFreeSql 进行依赖注入，例如 .net 6 的 ASP.NET Core 程序中：

builder.Services
    .AddFreeSql(builder.Configuration);

后面就是可以通过构造函数注入，或者直接在控制器中使用：

    /// <summary>
    /// 测试数据库连接
    /// </summary>
    /// <param name="resolver"></param>
    /// <param name="key"></param>
    /// <returns>数据库连接是否可用</returns>
    [HttpGet]
    public bool TestDbConnect([FromServices] FreeSqlResolver resolver, string key)
    {
        if (key == null) throw new ArgumentNullException(nameof(key));
        var freeSql = resolver(key);
        return freeSql.Ado.ExecuteConnectTest();
    }

[luoyunchong]

      .AddSingleton<FreeSqlResolver>(provider => key =>

这里似乎有语法错误

[hd2y]

没有额，返回值是一个委托，所以是这个样子。

后面项目上不用委托这种写法了，没办法显式释放，写一个带
IFreeSql GetFreeSql(string db) 方法的工厂类。

[luoyunchong]

我这边复制这个扩展提示有语法错误

[lxh023]

.AddSingleton(provider => key =>
看起来好像是：
.AddSingleton( key =>