动手造轮子：给微软的日志框架写一个基于委托的日志提供者

动手造轮子：给微软的日志框架写一个基于委托的日志提供者

Intro

微软的日志框架现在已经比较通用，有时候我们不想使用外部的日志提供者，但又希望提供一个比较简单的委托就可以实现日志记录，于是就有了后面的探索和实现。

Solution

基于委托的 LoggerProvider 实现代码:

[ProviderAlias("Delegate")]
public class DelegateLoggerProvider : ILoggerProvider
{
    private readonly Action<string, LogLevel, Exception, string> _logAction;
    private readonly ConcurrentDictionary<string, DelegateLogger> _loggers = new ConcurrentDictionary<string, DelegateLogger>();

    public DelegateLoggerProvider(Action<string, LogLevel, Exception, string> logAction)
    {
        _logAction = logAction;
    }

    public void Dispose()
    {
        _loggers.Clear();
    }

    public ILogger CreateLogger(string categoryName)
    {
        return _loggers.GetOrAdd(categoryName, category => new DelegateLogger(category, _logAction));
    }

    private class DelegateLogger : ILogger
    {
        private readonly string _categoryName;
        private readonly Action<string, LogLevel, Exception, string> _logAction;

        public DelegateLogger(string categoryName, Action<string, LogLevel, Exception, string> logAction)
        {
            _categoryName = categoryName;
            _logAction = logAction;
        }

        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter)
        {
            if (null != _logAction)
            {
                var msg = formatter(state, exception);
                _logAction.Invoke(_categoryName, logLevel, exception, msg);
            }
        }

        public bool IsEnabled(LogLevel logLevel)
        {
            return true;
        }

        public IDisposable BeginScope<TState>(TState state)
        {
            return NullScope.Instance;
        }
    }
}

使用示例

ILoggerFactory loggerFactory = new LoggerFactory();
//loggerFactory.AddConsole();
loggerFactory.AddDelegateLogger(
    (category, logLevel, exception, msg) =>
    {
        Console.WriteLine($"{category}:[{logLevel}] {msg}\n{exception}");
    }
);

日志输出效果如下：

Reference

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本文链接：https://www.cnblogs.com/weihanli/p/delegate-logger-provider-for-microsoft-logging.html