三种配置其实都是为了注入日志相关的服务，但是调用的方法稍有不同。现在我们以第二种配置来详细看看其注入过程。首先调用AddLogging方法,其实现源码如下：
public static IServiceCollection AddLogging(this IServiceCollection services, Action<ILoggingBuilder> configure) { services.AddOptions();//这里会注入最基础的5个服务 option相关服务只要是跟配置文件相关，通过Option服务获取相关配置文件参数参数 services.TryAdd(ServiceDescriptor.Singleton<ILoggerFactory, LoggerFactory>()); services.TryAdd(ServiceDescriptor.Singleton(typeof(ILogger<>), typeof(Logger<>))); services.TryAddEnumerable(ServiceDescriptor.Singleton<IConfigureOptions<LoggerFilterOptions>>(new DefaultLoggerLevelConfigureOptions(LogLevel.Information))); configure(new LoggingBuilder(services)); return services; }
接着会调用AddConfiguration
public static ILoggingBuilder AddConfiguration(this ILoggingBuilder builder, IConfiguration configuration) { builder.AddConfiguration(); //下面为AddConfiguration的实现 public static void AddConfiguration(this ILoggingBuilder builder) { builder.Services.TryAddSingleton<ILoggerProviderConfigurationFactory, LoggerProviderConfigurationFactory>(); builder.Services.TryAddSingleton(typeof(ILoggerProviderConfiguration<>), typeof(LoggerProviderConfiguration<>)); } builder.Services.AddSingleton<IConfigureOptions<LoggerFilterOptions>>(new LoggerFilterConfigureOptions(configuration)); builder.Services.AddSingleton<IOptionsChangeTokenSource<LoggerFilterOptions>>(new ConfigurationChangeTokenSource<LoggerFilterOptions>(configuration)); builder.Services.AddSingleton(new LoggingConfiguration(configuration)); return builder; }
下面来看打印日志的具体实现：
public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter) { var loggers = Loggers; List<Exception> exceptions = null; //loggers为LoggerInformation数组，如果你在Startup中添加了Console、Deubg日志功能了，那loggers数组值有2个，就是它俩。 foreach (var loggerInfo in loggers) { //循环遍历每一种日志打印，如果满足些日子的条件，才执行打印log方法。比如某一个日志等级为Info, //但是Console配置的最低打印等级为Warning，Debug配置的最低打印等级为Debug //则Console中不会打印，Debug中会被打印 if (!loggerInfo.IsEnabled(logLevel)) { continue; } try { //每一种类型的日志，对应的打印方法不同。执行对应的打印方法 loggerInfo.Logger.Log(logLevel, eventId, state, exception, formatter); } catch (Exception ex) { if (exceptions == null) { exceptions = new List<Exception>(); } exceptions.Add(ex); } } }
下面具体看一下Console的打印实现：
首先ConsoleLogger实现了ILogger的Log方法，并在方法中调用WriteMessage方法
public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter) { //代码太多 我就省略一些判空代码 var message = formatter(state, exception); if (!string.IsNullOrEmpty(message) || exception != null) { WriteMessage(logLevel, Name, eventId.Id, message, exception); } } public virtual void WriteMessage(LogLevel logLevel, string logName, int eventId, string message, Exception exception) { ....... if (logBuilder.Length > 0) { var hasLevel = !string.IsNullOrEmpty(logLevelString); //这里是主要的代码实现，可以看到，并没有写日志的代码，而是将日志打入到一个BlockingCollection<LogMessageEntry>队列中 _queueProcessor.EnqueueMessage(new LogMessageEntry() { Message = logBuilder.ToString(), MessageColor = DefaultConsoleColor, LevelString = hasLevel ? logLevelString : null, LevelBackground = hasLevel ? logLevelColors.Background : null, LevelForeground = hasLevel ? logLevelColors.Foreground : null }); } ...... }
下面看日志被放入队列后的具体实现: