.NET CORE全局异常处理(自定义过滤器 ExceptionFilterAttribute、自定义中间件)配合log4net写日志

1、自定义中间件处理异常(推荐) 参考：https://www.csframework.com/archive/1/arc-1-20211230-4180.htm

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using System.Net; using System.Text.Json; using ExceptionHandling.Models.Responses;   namespace ExceptionHandling.Middlewares;   public class ExceptionHandlingMiddleware {     private readonly RequestDelegate _next;  // 用来处理上下文请求      private readonly ILogger<ExceptionHandlingMiddleware> _logger;     public ExceptionHandlingMiddleware(RequestDelegate next,ILogger<ExceptionHandlingMiddleware> logger)     {         _next = next;         _logger = logger;     }       public async Task InvokeAsync(HttpContext httpContext)     {         try         {             await _next(httpContext); //要么在中间件中处理，要么被传递到下一个中间件中去         }         catch (Exception ex)         {             //_logger.LogError(ex, "##异常来源：{0}", httpContext.Request.Path);//直接记录ex             await HandleExceptionAsync(httpContext, ex); // 捕获异常了在HandleExceptionAsync中处理         }     }     private async Task HandleExceptionAsync(HttpContext context, Exception exception)     {         context.Response.ContentType = "application/json";  // 返回json 类型         var response = context.Response;           var errorResponse = new ErrorResponse         {             Success = false         };  // 自定义的异常错误信息类型         switch (exception)         {             case ApplicationException ex:                 if (ex.Message.Contains("Invalid token"))                 {                     response.StatusCode = (int) HttpStatusCode.Forbidden;                     errorResponse.Message = ex.Message;                     break;                 }                 response.StatusCode = (int) HttpStatusCode.BadRequest;                 errorResponse.Message = ex.Message;                 break;             case KeyNotFoundException ex:                 response.StatusCode = (int) HttpStatusCode.NotFound;                 errorResponse.Message = ex.Message;                 break;             default:                 response.StatusCode = (int) HttpStatusCode.InternalServerError;                 errorResponse.Message = "Internal Server errors. Check Logs!";                 break;         }         _logger.LogError(exception.Message);         var result = JsonSerializer.Serialize(errorResponse);         await context.Response.WriteAsync(result);     } }  public class ErrorResponse {     public int StatusCode { get; set; }     public string Message { get; set; } = string.Empty;     public bool Success { get; set; } }

注入中间件
方式1：app.UseMiddleware<ExceptionHandlingMiddleware>();然后在Action或者Service中直接抛异常，就会走异常处理。
方式2：使用扩展方法

// Extension method used to add the middleware to the HTTP request pipeline.
    public static class ExceptionHandlingMiddlewareExtensions
    {
        public static IApplicationBuilder UseExceptionHandlingMiddleware(this IApplicationBuilder builder)
        {
            return builder.UseMiddleware<ExceptionHandlingMiddleware>();
        }
    }

2、使用过滤器 参考：https://blog.csdn.net/Daniel_yka/article/details/121062319

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public class CustomExceptionFilterAttribute: ExceptionFilterAttribute {   private readonly ILogger<WeatherForecastController> _logger;   public CustomExceptionFilterAttribute(ILogger<WeatherForecastController> logger)   {     _logger = logger;   }   public override void OnException(ExceptionContext context)   {     //判断该异常有没有处理     if (!context.ExceptionHandled)     {       _logger.LogError($"Path:{context.HttpContext.Request.Path}Message:{context.Exception.Message}");       context.Result = new JsonResult(new {Reslut = false,Msg = "发生异常，请联系管理员"});       context.ExceptionHandled = true;     }   } }

然后再在Startup下面的ConfigureServices注册这个类:services.AddControllers(o=>o.Filters.Add(typeof(CustomExceptionFilterAttribute)));
此时当程序中有异常，便会进入该方法，我们就能在这里统一管理异常。
log4net使用：
引入包：Microsoft.Extensions.Logging
Microsoft.Extensions.Logging.Log4Net.AspNetCore
配置日志

builder.Host.ConfigureDefaults(args).ConfigureLogging(p =>
{
    p.AddFilter("System", LogLevel.Warning); //过滤掉系统默认的一些日志
    p.AddFilter("Microsoft", LogLevel.Warning);//过滤掉系统默认的一些日志
    var path = Directory.GetCurrentDirectory() + "\\log4net.config";
    //不带参数：表示log4net.config的配置文件就在应用程序根目录下，也可以指定配置文件的路径
    p.AddLog4Net(path);
});

根目录log4net.config

<log4net>
    <appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender">
        <layout type="log4net.Layout.PatternLayout" value="%date [%thread] %-5level %logger - %message%newline" />
    </appender>

    <appender name="FileAppender" type="log4net.Appender.FileAppender">
        <file value="log-file.log" />
        <appendToFile value="true" />
        <layout type="log4net.Layout.PatternLayout">
            <conversionPattern value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline" />
        </layout>
    </appender>

    <appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
        <file value="logfile/" />
        <appendToFile value="true" />
        <rollingStyle value="Composite" />
        <staticLogFileName value="false" />
        <datePattern value="yyyyMMdd'.log'" />
        <maxSizeRollBackups value="10" />
        <maximumFileSize value="1MB" />
        <layout type="log4net.Layout.PatternLayout">
            <conversionPattern value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline" />
        </layout>
    </appender>

    <!-- Setup the root category, add the appenders and set the default level -->
    <root>
        <level value="ALL" />
        <appender-ref ref="ConsoleAppender" />
        <appender-ref ref="FileAppender" />
        <appender-ref ref="RollingLogFileAppender" />
    </root>
</log4net>

构造函数注入：private readonly ILogger<HomeController> _logger;
_logger.LogInformation("test log info");