最近又研究了一下.NetCore配置选项的源码实现，又学习到了不少东西。这篇文章先写一下IConfiguration的学习成果，Options的后面补上
下面是ConfigurationBuilder中的主要代码
可以看到ConfigurationBuilder的主要功能就是配置数据源到集合中
在Build时依次调用IConfigurationSource的Build函数，并将返回的IConfigurationProvider加入到List中
最后用IConfigurationProvider的集合构建一个ConfigurationRoot对象
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;
}
}
}
}
上面展示了比较常用的三种ConfigurationSource，代码都比较简单。
也很容易看出来ConfigurationSource的作用就是配置数据源，并不解析数据。
解析数据源的功能由 IConfigurationProvider完成
下面为IConfigurationProvider接口定义的5个函数
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);
}
ConfigurationProvider是一个抽象类，继承了IConfigurationProvider接口
在新建Provider时一般都会选择直接继承ConfigurationProvider，接下来看一下ConfigurationProvider的几个核心方法
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();
}
可以推测出：
在ConfigurationBuilder的Build函数中，我们生成了一个ConfigurationRoot，并给他传递了所有的ConfigrationProvider列表，下面我们看看他用我们的Provider都做了啥吧
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;
上面的代码也对部分地方进行了简化。可以看到ConfigurationRoot在生成时主要就做了两件事
至此配置的数据源构建这块就分析完啦！
常规的配置查询有两种基本方式 ：索引器和GetSection(string key)
其余的GetValue等等都是一些扩展方法，本篇文章不对此进行展开研究
索引器的查询执行的方式是倒叙查询所有的Provider，然后调用Provider的TryGet函数，在查询时重名的Key，最后加入的会生效。
赋值则是依次调用每个Provider的Set函数
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();
}
}
可以看到GetSection会生成一个ConfigurationSection对象
而ConfigurationSection在读取/设置值时实际上就是对查询的Key用:拼接，然后调用IConfigurationRoot（_root）的赋值或查询函数
关于Configuration的配置和读取的知识点大概就是以上这些了，还有更深入的涉及到对象的绑定这一块Get<> Bind<> GetChildren()等，比较难读，要一行一行代码看，以后有时间可能再研究一下
最后贴上一个从数据加载配置源并动态更新的小例子
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);
}
}
