asp.net core 将配置文件配置迁移到数据库(一)

asp.net core 将配置文件配置迁移到数据库(一)

Intro

asp.net core 配置默认是项目根目录下的 appsettings.json 文件,还有环境变量以及 command line arguments,有一些链接字符串等信息可能放在数据库里更好一些,也方便修改与维护,有的配置可能多个应用共享一些配置,这样维护在数据库里可能就只需要配置一次。有人可能说那你为什么不直接搞个配置中心呢,开始是想直接接入一个配置中心,后来觉得项目不大可以不必引入配置中心,直接自己造个轮子从数据库读取配置就可以了,于是就想自己实现一套基于数据库的 ConfigurationProvider

探索 Configuration

Configuration 源码在 https://github.com/aspnet/Extensions/tree/master/src/Configuration

微软也提供了一些自己实现的 ConfigurationProvider

自定义基于 EF 的 ConfigurationProvider

需要实现两个接口

  1. 实现 IConfigurationProvider 接口
using System.Linq;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;

namespace WeihanLi.Configuration.EntityFramework
{
    internal class EntityFrameworkConfigurationProvider : ConfigurationProvider
    {
        private readonly DbContextOptions<ConfigurationsDbContext> _dbContextOptions;

        public EntityFrameworkConfigurationProvider(DbContextOptions<ConfigurationsDbContext> dbContextOptions)
        {
            _dbContextOptions = dbContextOptions;
        }

        public override void Load()
        {
            using (var dbContext = new ConfigurationsDbContext(_dbContextOptions))
            {
                var configurations = dbContext.Configurations.AsNoTracking()
                    .ToArray();
                if (configurations.Length == 0)
                    return;

                foreach (var configuration in configurations)
                {
                    Data[configuration.Key] = configuration.Value;
                }
            }
        }
    }
}
  1. 实现 IConfigurationSource 接口
using System;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;

namespace WeihanLi.Configuration.EntityFramework
{
    internal class EntityFrameworkConfigurationSource : IConfigurationSource
    {
        private readonly Action<DbContextOptionsBuilder<ConfigurationsDbContext>> _action;

        public EntityFrameworkConfigurationSource(Action<DbContextOptionsBuilder<ConfigurationsDbContext>> action)
        {
            _action = action;
        }

        private readonly DbContextOptionsBuilder<ConfigurationsDbContext> DbContextOptionsBuilder = new DbContextOptionsBuilder<ConfigurationsDbContext>();

        public IConfigurationProvider Build(IConfigurationBuilder builder)
        {
            _action.Invoke(DbContextOptionsBuilder);
            return new EntityFrameworkConfigurationProvider(DbContextOptionsBuilder.Options);
        }
    }
}

扩展方法:

using System;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;

namespace WeihanLi.Configuration.EntityFramework
{
    public static class RedisConfigurationExtension
    {
        /// <summary>
        /// Adds an <see cref=\"IConfigurationProvider\"/> that reads configuration values from EntityFramework.
        /// </summary>
        /// <param name=\"builder\">The <see cref=\"IConfigurationBuilder\"/> to add to.</param>
        /// <param name=\"action\">Configures the configurationsDbContext source.</param>
        /// <returns>The <see cref=\"IConfigurationBuilder\"/>.</returns>
        public static IConfigurationBuilder AddEntityFramework(this IConfigurationBuilder builder, Action<DbContextOptionsBuilder<ConfigurationsDbContext>> action)
            => builder.Add(new EntityFrameworkConfigurationSource(action));
    }
}

更多源码参考:https://github.com/WeihanLi/AspNetCorePlayground/tree/master/WeihanLi.Configuration.EntityFramework

使用

修改 Program 文件 WebHost 的构建,参考https://github.com/WeihanLi/AspNetCorePlayground/blob/master/TestWebApplication/Program.cs

WebHost.CreateDefaultBuilder(args)
                .ConfigureAppConfiguration(configBuilder =>
                {
                    var configuration = configBuilder.Build();
                    configBuilder.AddEntityFramework(config => config.UseSqlServer(configuration.GetConnectionString(\"Configurations\"));
                })
                .UseStartup<Startup>();

源码

你可以修改源码来进一步定制符合你需要的基于数据库的 ConfigurationProvider

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