.Net Core配置Configuration具体实现

public IList<IConfigurationSource> Sources = new List<IConfigurationSource>();

public IConfigurationBuilder Add(IConfigurationSource source)
{
    Sources.Add(source);
    return this;
}

public IConfigurationRoot Build()
{
    List<IConfigurationProvider> list = new List<IConfigurationProvider>();
    foreach (IConfigurationSource source in Sources)
    {
        IConfigurationProvider item = source.Build(this);
        list.Add(item);
    }

    return new ConfigurationRoot(list);
}

public class EnvironmentVariablesConfigurationSource : IConfigurationSource
{
    public string Prefix;
    public IConfigurationProvider Build(IConfigurationBuilder builder)
    {
        return new EnvironmentVariablesConfigurationProvider(Prefix);
    }
    public EnvironmentVariablesConfigurationSource()
    {
    }
}
    
   
public class CommandLineConfigurationSource : IConfigurationSource
{
    public IDictionary<string, string> SwitchMappings;
    public IEnumerable<string> Args;
    public IConfigurationProvider Build(IConfigurationBuilder builder)
    {
        return new CommandLineConfigurationProvider(Args, SwitchMappings);
    }
    public CommandLineConfigurationSource()
    {
    }
}

//JsonConfigurationSource继承自FileConfigurationSource，我这里将其合为一个了
public abstract class JsonConfigurationSource : IConfigurationSource
{
 public IFileProvider FileProvider { get; set; }
 public string Path { get; set; }
 public bool Optional { get; set; }
 public bool ReloadOnChange { get; set; }
 public int ReloadDelay { get; set; } = 250;

 public Action<FileLoadExceptionContext> OnLoadException { get; set; }
    
 public IConfigurationProvider Build(IConfigurationBuilder builder)
 {
  FileProvider = FileProvider ?? builder.GetFileProvider();
  OnLoadException = OnLoadException ?? builder.GetFileLoadExceptionHandler();
  return new JsonConfigurationProvider(this);
 }
    
 public void ResolveFileProvider()
 {
  if (FileProvider == null && !string.IsNullOrEmpty(Path) && System.IO.Path.IsPathRooted(Path))
  {
   string directoryName = System.IO.Path.GetDirectoryName(Path);
   string text = System.IO.Path.GetFileName(Path);
   while (!string.IsNullOrEmpty(directoryName) && !Directory.Exists(directoryName))
   {
    text = System.IO.Path.Combine(System.IO.Path.GetFileName(directoryName), text);
    directoryName = System.IO.Path.GetDirectoryName(directoryName);
   }
   if (Directory.Exists(directoryName))
   {
    FileProvider = new PhysicalFileProvider(directoryName);
    Path = text;
   }
  }
 }
}

public interface IConfigurationProvider
{
 bool TryGet(string key, out string value);

 void Set(string key, string value);

 IChangeToken GetReloadToken();

 void Load();

 IEnumerable<string> GetChildKeys(IEnumerable<string> earlierKeys, string parentPath);
}

public abstract class ConfigurationProvider : IConfigurationProvider
{
 private ConfigurationReloadToken _reloadToken = new ConfigurationReloadToken();
    
 protected IDictionary<string, string> Data= new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);

 public virtual bool TryGet(string key, out string value)=>Data.TryGetValue(key, out value);

 public virtual void Set(string key, string value)=>Data[key] = value;

 public virtual void Load(){}

 public IChangeToken GetReloadToken()
 {
  return _reloadToken;
 }
 
 protected void OnReload()
 {
 ConfigurationReloadToken configurationReloadToken = Interlocked.Exchange(ref _reloadToken, new ConfigurationReloadToken());
  configurationReloadToken.OnReload();
 }

private ConfigurationReloadToken _changeToken = new ConfigurationReloadToken();

public ConfigurationRoot(IList<IConfigurationProvider> providers)
{
    _providers = providers;
    _changeTokenRegistrations = new List<IDisposable>(providers.Count);
    foreach (IConfigurationProvider p in providers)
    {
        p.Load();
        ChangeToken.OnChange(p.GetReloadToken, 
           delegate{
     var oldToken=Interlocked.Exchange(ref _changeToken, new ConfigurationReloadToken());
                 oldToken.OnReload();
                })
    }
}

public IChangeToken GetReloadToken()=>_changeToken;

public string this[string key]
{
 get
 {
  for (int num = _providers.Count - 1; num >= 0; num--)
  {
   if (_providers[num].TryGet(key, out var value))
   {
    return value;
   }
  }
  return null;
 }
 set
 {
  foreach (IConfigurationProvider provider in _providers)
  {
   provider.Set(key, value);
  }
 }
}

public IConfigurationSection GetSection(string key)
{
 return new ConfigurationSection(this, key);
}

public class ConfigurationSection : IConfigurationSection, IConfiguration
{
 private readonly IConfigurationRoot _root;
 private readonly string _path;
 private string _key;
 public string Value
 {
  get
  {
   return _root[Path];
  }
  set
  {
   _root[Path] = value;
  }
 }
 
    //ConfigurationPath.Combine = string.Join(":",paramList);
 public string this[string key]
 {
  get
  {
   return _root[ConfigurationPath.Combine(Path, key)];
  }
  set
  {
   _root[ConfigurationPath.Combine(Path, key)] = value;
  }
 }

 public ConfigurationSection(IConfigurationRoot root, string path)
 {
  _root = root;
  _path = path;
 }

 public IConfigurationSection GetSection(string key)
 {
  return _root.GetSection(ConfigurationPath.Combine(Path, key));
 }

 public IEnumerable<IConfigurationSection> GetChildren()
 {
  return _root.GetChildrenImplementation(Path);
 }

 public IChangeToken GetReloadToken()
 {
  return _root.GetReloadToken();
 }
}

 public void Run()
 {
     var builder = new ConfigurationBuilder();
     var dataProvider = new DBDataProvider();
     builder.Sources.Add(new DBConfigurationSource() { DataProvider = dataProvider, ReloadOnChange = true, Table = "config" });
     IConfigurationRoot config = builder.Build();

     Console.WriteLine(config["time"]);
     Task.Run(() =>
              {
                  while (true)
                  {
                      Thread.Sleep(2000);
                      dataProvider.Update("config");
                      Console.WriteLine($"读取配置时间：{config["time"]}");
                  }
              });
     Thread.Sleep(20000);
 }
public class DBConfigurationProvider : ConfigurationProvider
{
    private DBConfigurationSource Source { get; }
    public DBConfigurationProvider(DBConfigurationSource source)
    {
        Source = source;
    }

    public override void Load()
    {
        if (Source.ReloadOnChange)
        {
            ChangeToken.OnChange(() => Source.DataProvider.Watch(Source.Table), LoadData);
        }
        LoadData();
    }

    private void LoadData()
    {
        var data = Source.DataProvider.GetData(Source.Table);
        Load(data);
        OnReload();
    }

    public void Load(Dictionary<string, object> data)
    {
        var dic = new SortedDictionary<string, string>(StringComparer.OrdinalIgnoreCase);
        foreach (var element in data)
        {
            dic.Add(element.Key, element.Value?.ToString());
        }
        base.Data = dic;
    }
}

public class DBConfigurationSource : IConfigurationSource
{
    public DBDataProvider DataProvider { get; set; }
    public string Table { get; set; }
    public bool ReloadOnChange { get; set; }
    public bool Optional { get; set; }

    public DBConfigurationSource()
    {
    }

    public IConfigurationProvider Build(IConfigurationBuilder builder)
    {
        return new DBConfigurationProvider(this);
    }
}

public class DBDataProvider
{
    private ConcurrentDictionary<string, CancellationTokenSource> tableToken = new ConcurrentDictionary<string, CancellationTokenSource>();
    public DBDataProvider()
    {
    }

    public Dictionary<string, object> GetData(string table)
    {
        switch (table)
        {
            case "config":
                return GetConfig();
        }
        return new Dictionary<string, object>();
    }

    public void Update(string table)
    {
        Console.WriteLine($"更新数据库数据table:{table}");
        if (tableToken.TryGetValue(table, out CancellationTokenSource cts))
        {
            var oldCts = cts;
            tableToken[table] = new CancellationTokenSource();
            oldCts.Cancel();
        }
    }

    private Dictionary<string, object> GetConfig()
    {
        var valueDic = new Dictionary<string, object>();
        valueDic.TryAdd("time", DateTime.Now.ToString());
        valueDic.TryAdd("weather", "windy");
        valueDic.TryAdd("people_number:male", 100);
        valueDic.TryAdd("people_number:female", 150);
        return valueDic;
    }

    public IChangeToken Watch(string table)
    {
        var cts = tableToken.GetOrAdd(table, x => new CancellationTokenSource());
        return new CancellationChangeToken(cts.Token);
    }
}