.Net Core 自定义记录器循环依赖注入参考/无限循环

Question

我试图编写一个客户 ILogger / ILoggerProvider，它依赖于一个依赖于 ILogger 的服务 :) 这给我留下了循环引用和无限循环。

如何修改此代码以避免循环引用？

class Program
    {
        static void Main(string[] args)
        {
            var configuration = new ConfigurationBuilder().SetBasePath(Directory.GetCurrentDirectory()).AddJsonFile("appsettings.json").Build();

            var serviceCollection = new ServiceCollection();

            serviceCollection.AddSingleton<IDependentOnLoggerService, MyService>();

            serviceCollection.AddLogging(loggingBuilder =>
            {
                loggingBuilder.AddConfiguration(configuration.GetSection("Logging"));
                loggingBuilder.AddConsole();
            });

            serviceCollection.AddCustomLogger();

            using (var serviceProvider = serviceCollection.BuildServiceProvider())
            {
                var loggerFactory = serviceProvider.GetService<ILoggerFactory>();
                var logger = loggerFactory.CreateLogger<Program>();

                logger.LogInformation("hello world");
            }
        }
    }

    public interface IDependentOnLoggerService
    {
        void DoWork();
    }

    public class MyService : IDependentOnLoggerService
    {
        private ILogger logger;

        public MyService(ILoggerFactory loggerFactory)
        {
            this.logger = loggerFactory.CreateLogger<MyService>();
            this.logger.LogInformation("MyService create");
        }

        public void DoWork()
        {
            this.logger.LogInformation("Doing work");
        }
    }

    public static class ServiceCollectionExtensions
    {
        public static void AddCustomLogger(this IServiceCollection serviceCollection)
        {
            serviceCollection.AddLogging(loggingBuilder =>
            {
                loggingBuilder.AddCustomLogger();
            });
        }

        private static ILoggingBuilder AddCustomLogger(this ILoggingBuilder builder)
        {
            if (builder == null)
            {
                throw new ArgumentNullException(nameof(builder));
            }

            builder.Services.TryAddEnumerable(ServiceDescriptor.Singleton<ILoggerProvider, CustomLoggerProvider>(
                serviceProvider =>
                {
                    // this causes circulation dependency injection, resolving IDependentOnLoggerService will try to resolve an ILogger which will bring it right back here
                    var loggerDependentService = serviceProvider.GetService<IDependentOnLoggerService>(); 

                    return new CustomLoggerProvider(loggerDependentService);
                }));

            return builder;
        }
    }

    public class CustomLoggerProvider : ILoggerProvider
    {
        IDependentOnLoggerService dependentOnLoggerService;

        public CustomLoggerProvider(IDependentOnLoggerService dependentOnLoggerService)
        {
            this.dependentOnLoggerService = dependentOnLoggerService;
        }

        public ILogger CreateLogger(string categoryName)
        {
            return new CustomLogger(this.dependentOnLoggerService);
        }

        public void Dispose() { }
    }

    public class CustomLogger : ILogger
    {
        IDependentOnLoggerService dependentOnLoggerService;

        public CustomLogger(IDependentOnLoggerService dependentOnLoggerService)
        {
            this.dependentOnLoggerService = dependentOnLoggerService;
        }

        public IDisposable BeginScope<TState>(TState state)
        {
            return null;
        }

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

        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter)
        {
            this.dependentOnLoggerService.DoWork();
            Console.WriteLine(state.ToString());
        }
    }

如果可能，我想保持结构相似，而不是用通用主机和 IHostBuilder 重写。

Answer 1

你可以有一个第三个类来引用这两个服务，你只需要在你需要服务的地方依赖注入这个类。

一个类似的问题here，你可以看看。