本节主要介绍解决方案中的Microsoft.Framework.Logging.Abstractions、Microsoft.Framework.Logging俩个工程。
这俩个工程中所有类的关系如下图所示：
![[Asp.net 5] Logging-日志系统的基本架构（上）](https://image.miaokee.com:8440/aHR0cHM6Ly9pbWFnZXMwLmNuYmxvZ3MuY29tL2Jsb2cyMDE1LzcxNTQwNC8yMDE1MDYvMDMxNjU1MjU2NDgyNDYyLngtcG5n.x-png?w=700&webp=1 "[Asp.net 5] Logging-日志系统的基本架构（上）")
首先我们可以发现处于核心的是中间的四个接口：ILogger、ILoggerFactory、ILoggerProvider、ILogValues。
- ILogger：记录日志的接口，所以写日志的类都该实现该接口，工程中有俩个类实现了该接口：Logger、Logger<T>
- ILoggerFactory：创建ILogger的工厂。负责创建工厂的逻辑，但是一般不直接创建，而是调用内部ILoggerProvider去完成。
- ILoggerProvider：能够直接创建ILogger实例，做为属性添加到ILoggerFactory中，ILogger的具体逻辑受控制ILoggerFactory。
- ILogValues：在Logger的扩展方法中作为特殊类型的object传入，作为日志的数据源。
接口的定义源码如下：
public interface ILogger
{
void Log(LogLevel logLevel, int eventId, object state, Exception exception, Func<object, Exception, string> formatter); bool IsEnabled(LogLevel logLevel); IDisposable BeginScopeImpl(object state);
}
ILogger
public interface ILoggerFactory
{
LogLevel MinimumLevel { get; set; } ILogger CreateLogger(string categoryName); void AddProvider(ILoggerProvider provider);
}
ILoggerFactory
public interface ILoggerProvider
{
ILogger CreateLogger(string name);
}
ILoggerProvider
public interface ILogValues
{
IEnumerable<KeyValuePair<string, object>> GetValues();
}
ILogValues
ILogger以及实现类
ILogger接口、ILogger<TCategoryName>（没有任何定义）、Logger<T>这种泛型继承是否有相识之感，之前的博客文章中已经对于这种情况有所介绍（[Asp.net 5] Localization-resx资源文件的管理中IStringLocalizer 、IStringLocalizer<T> 、StringLocalizer<TResourceSource>是一致的）。实际Logger<T>中T是ILogger的实例子类，实际就是使用代理模式，内部包含ILogger实例，并且所有对外的方法都仅仅是内部ILogger实例的封装。
public class Logger<T> : ILogger<T>
{
private readonly ILogger _logger; /// <summary>
/// Creates a new <see cref="Logger{T}"/>.
/// </summary>
/// <param name="factory">The factory.</param>
public Logger(ILoggerFactory factory)
{
_logger = factory.CreateLogger<T>();
} IDisposable ILogger.BeginScopeImpl(object state)
{
return _logger.BeginScopeImpl(state);
} bool ILogger.IsEnabled(LogLevel logLevel)
{
return _logger.IsEnabled(logLevel);
} void ILogger.Log(LogLevel logLevel, int eventId, object state, Exception exception, Func<object, Exception, string> formatter)
{
_logger.Log(logLevel, eventId, state, exception, formatter);
}
}
Logger
Logger类同样实现了ILogger接口，也同样使用了代理模式，不过不同于Logger<T>泛型，Logger类有自己的内部逻辑。而是在内部封装了 ILogger[] _loggers对象。使得Logger更像LoggerManage。但是由于Logger同样实现Logger接口，所以Logger类是管理其它Logger类的代理。而Logger内部的_loggers是通过LoggerFactory对象封装的。当记录日志时，依次遍历内部的 _loggers对象，进行写日志操作。
internal class Logger : ILogger
{
private readonly LoggerFactory _loggerFactory;
private readonly string _name;
private ILogger[] _loggers = new ILogger[]; public Logger(LoggerFactory loggerFactory, string name)
{
_loggerFactory = loggerFactory;
_name = name; var providers = loggerFactory.GetProviders();
_loggers = new ILogger[providers.Length];
for (var index = ; index != providers.Length; index++)
{
_loggers[index] = providers[index].CreateLogger(name);
}
} public void Log(LogLevel logLevel, int eventId, object state, Exception exception, Func<object, Exception, string> formatter)
{
if (logLevel >= _loggerFactory.MinimumLevel)
{
foreach (var logger in _loggers)
{
logger.Log(logLevel, eventId, state, exception, formatter);
}
}
} public bool IsEnabled(LogLevel logLevel)
{
if (logLevel < _loggerFactory.MinimumLevel)
{
return false;
}
foreach (var logger in _loggers)
{
if (logger.IsEnabled(logLevel))
{
return true;
}
}
return false;
} public IDisposable BeginScopeImpl(object state)
{
var loggers = _loggers;
var scope = new Scope(loggers.Length);
for (var index = ; index != loggers.Length; index++)
{
scope.SetDisposable(index, loggers[index].BeginScopeImpl(state));
}
return scope;
} internal void AddProvider(ILoggerProvider provider)
{
var logger = provider.CreateLogger(_name);
_loggers = _loggers.Concat(new[] { logger }).ToArray();
} private class Scope : IDisposable
{
private bool _isDisposed; private IDisposable _disposable0;
private IDisposable _disposable1;
private readonly IDisposable[] _disposable; public Scope(int count)
{
if (count > )
{
_disposable = new IDisposable[count - ];
}
} public void SetDisposable(int index, IDisposable disposable)
{
if (index == )
{
_disposable0 = disposable;
}
else if (index == )
{
_disposable1 = disposable;
}
else
{
_disposable[index - ] = disposable;
}
} protected virtual void Dispose(bool disposing)
{
if (!_isDisposed)
{
if (disposing)
{
if (_disposable0 != null)
{
_disposable0.Dispose();
}
if (_disposable1 != null)
{
_disposable1.Dispose();
}
if (_disposable != null)
{
var count = _disposable.Length;
for (var index = ; index != count; ++index)
{
if (_disposable[index] != null)
{
_disposable[index].Dispose();
}
}
}
} _isDisposed = true;
}
} // This code added to correctly implement the disposable pattern.
public void Dispose()
{
// Do not change this code. Put cleanup code in Dispose(bool disposing) above.
Dispose(true);
// TODO: tell GC not to call its finalizer when the above finalizer is overridden.
// GC.SuppressFinalize(this);
} internal void Add(IDisposable disposable)
{
throw new NotImplementedException();
}
}
}
Logger
ILoggerFactory以及实现类
ILoggerFactory主要有俩个作用，添加新的ILoggerProvider，创建ILogger。而ILoggerFactory的唯一实现类LoggerFactory，简单实现了上面两个功能，并且在LoggerFactory内部额外维护_loggers副本，该处loggers都是Logger类型（非泛型），只是categoryName不同。所以通过LoggerFactory创建的Logger如下图所示：
![[Asp.net 5] Logging-日志系统的基本架构（上）](https://image.miaokee.com:8440/aHR0cHM6Ly9pbWFnZXMwLmNuYmxvZ3MuY29tL2Jsb2cyMDE1LzcxNTQwNC8yMDE1MDYvMDMyMjU5NTQzNjc3OTExLnBuZw%3D%3D.png?w=700&webp=1 "[Asp.net 5] Logging-日志系统的基本架构（上）")
public class LoggerFactory : ILoggerFactory
{
private readonly Dictionary<string, Logger> _loggers = new Dictionary<string, Logger>(StringComparer.Ordinal);
private ILoggerProvider[] _providers = new ILoggerProvider[];
private readonly object _sync = new object(); public ILogger CreateLogger(string categoryName)
{
Logger logger;
lock (_sync)
{
if (!_loggers.TryGetValue(categoryName, out logger))
{
logger = new Logger(this, categoryName);
_loggers[categoryName] = logger;
}
}
return logger;
} public LogLevel MinimumLevel { get; set; } = LogLevel.Verbose; public void AddProvider(ILoggerProvider provider)
{
lock (_sync)
{
_providers = _providers.Concat(new[] { provider }).ToArray();
foreach (var logger in _loggers)
{
logger.Value.AddProvider(provider);
}
}
} internal ILoggerProvider[] GetProviders()
{
return _providers;
}
}
LoggerFactory