aspnetcore配置log4net并添加全局异常处理

第一步：在NuGet中引用log4net

第二步：创建log4net.config

xml version="1.0" encoding="utf-8"?>
<configuration>
  <log4net>
    
    <logger name="Error">
      <level value="ALL" />
      <appender-ref ref="ErrorAppender" />
    logger>
    
    <appender name="ErrorAppender" type="log4net.Appender.RollingFileAppender">
      
      <param name="File" value="Logs\\Error\\" />
      
      <param name="AppendToFile" value="true" />
      
      <param name="MaxSizeRollBackups" value="1000" />
      
      <param name="MaxFileSize" value="10240" />
      
      <param name="StaticLogFileName" value="false" />
      
      <param name="DatePattern" value="yyyy-MM-dd.'log'" />
      
      <param name="RollingStyle" value="Date" />
      
      <layout type="log4net.Layout.PatternLayout">
        <param name="ConversionPattern" value="%n＝＝＝＝＝＝＝＝＝＝%n【日志级别】：%-5level%n【记录时间】：%date %n【执行时间】：[%r]毫秒%n%message%n" />
      layout>
    appender>

    
    <logger name="Info">
      <level value="ALL" />
      <appender-ref ref="InfoAppender" />
    logger>
    
    <appender name="InfoAppender" type="log4net.Appender.RollingFileAppender">
      
      <param name="File" value="Logs\\Info\\" />
      
      <param name="AppendToFile" value="true" />
      
      <param name="MaxSizeRollBackups" value="100" />
      <param name="MaxFileSize" value="1" />
      
      <param name="StaticLogFileName" value="false" />
      
      <param name="DatePattern" value="yyyy-MM-dd.'log'" />
      
      <param name="RollingStyle" value="Date" />
      
      <layout type="log4net.Layout.PatternLayout">
        <param name="ConversionPattern" value="%n＝＝＝＝＝＝＝＝＝＝%n【日志级别】：%-5p%n【记录时间】：%d [%t]%n【信息详情】：%m%n"  />
      layout>
    appender>
  log4net>
configuration>

第三步：新建Log4NetConfig.cs类，这里我是把工厂名放在配置文件中获取，一般情况下不需要这样操作，直接在代码内写死即可。

using log4net;
using log4net.Config;
using Microsoft.Extensions.Configuration;
using System;
using System.IO;

namespace Taoxue.SchoolRoll.Website
{
    public class Log4NetConfig
    {
        public static string RepositoryName { get; set; }

        public static void Init(IConfiguration configuration)
        {
            var repositoryName = configuration.GetSection("Log4Net:RepositoryName").Value;
            if (string.IsNullOrWhiteSpace(repositoryName))
            {
                throw new Exception("必须在配置文件中添加 Log4Net > RepositoryName 节点");
            }

            RepositoryName = repositoryName;

            var configFilePath = configuration.GetSection("Log4Net:ConfigFilePath").Value;
            if (string.IsNullOrWhiteSpace(configFilePath))
            {
                configFilePath = "log4net.config";
            }

            var file = new FileInfo(configFilePath);
            var repository = LogManager.CreateRepository(repositoryName);
            XmlConfigurator.Configure(repository, file);
        }
    }
}

第四步：在startup.cs中初始化配置

public Startup(IConfiguration configuration)
{
    Configuration = configuration;
    Log4NetConfig.Init(Configuration);
}

第五步：在appsettings.json中创建Log4net节点，注意，这里我是把log4net.config放在  站点根目录/Log4Net 目录下

"Log4Net": {
    "RepositoryName": "NETCoreRepository",
    "ConfigFilePath": "Log4Net/log4net.config" 
} 

第六步：创建Log4NetUtil.cs文件

using log4net;
using System;

namespace Taoxue.SchoolRoll.Website
{
    public class Log4NetUtil
    {
        private static readonly ILog ErrorLog = LogManager.GetLogger(Log4NetConfig.RepositoryName, "Error");

        private static readonly ILog InfoLog = LogManager.GetLogger(Log4NetConfig.RepositoryName, "Info");

        /// <summary>
        /// 全局异常错误记录持久化
        /// summary>
        /// <param name="throwMsg">param>
        /// <param name="ex">param>
        public static void LogError(string throwMsg, Exception ex)
        {
            var errorMsg =
                $"【抛出信息】：{throwMsg} \r\n【异常类型】：{ex.GetType().Name} \r\n【异常信息】：{ex.Message} \r\n【堆栈调用】：\r\n{ex.StackTrace}";
            ErrorLog.Error(errorMsg);
        }

        public static void LogInfo(string msg)
        {
            InfoLog.Info(msg);
        }
    }
}

至此，Log4Net配置完成，下面添加一个全局异常处理类测试下

using HZC.Core;
using HZC.Utils.Mvc;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Filters;
using System;

namespace Taoxue.SchoolRoll.Website.Extensions
{
    public class MvcGlobalExceptionFilter : IExceptionFilter
    {
        public void OnException(ExceptionContext context)
        {
            try
            {
                Log4NetUtil.LogError("Mvc全局异常", context.Exception);
                if (context.HttpContext.Request.IsAjax())
                {
                    context.Result = new JsonResult(ResultUtil.Fail(context.Exception.Message));
                }
                else
                {
                    context.Result = new RedirectToActionResult("Error", "Home", new { });
                }
            }
            catch (Exception e)
            {
                Console.WriteLine(e);
                throw;
            }
            context.ExceptionHandled = true; // 注意：如果不添加这句代码，程序不会自动断路，会继续向下进行。
        }
    }
}

在  startup.cs 的 ConfigureServices 中使用如下代码

services.AddMvc(option =>
    {
         option.Filters.Add<MvcGlobalExceptionFilter>();
    })             
    .SetCompatibilityVersion(CompatibilityVersion.Version_2_1);

修改  HomeController 的 Index ，手动抛出异常

public IActionResult Index()
{
    throw new Exception("异常测试");
    return View();
}

执行程序，在  根目录/Logs/Error 文件夹下查看生成的日志文件，发现已经写入如下内容

＝＝＝＝＝＝＝＝＝＝
【日志级别】：ERROR
【记录时间】：2019-05-16 00:40:49,071 
【执行时间】：[1750]毫秒
【抛出信息】：Mvc全局异常 
【异常类型】：Exception 
【异常信息】：异常测试 
【堆栈调用】：
   at Taoxue.SchoolRoll.Website.Controllers.HomeController.Index() in E:\项目\CSharp\xx\xxxx\Taoxue.SchoolRoll.Website\Controllers\HomeController.cs:line 19
   at lambda_method(Closure , Object , Object[] )
   at Microsoft.Extensions.Internal.ObjectMethodExecutor.Execute(Object target, Object[] parameters)
   at Microsoft.AspNetCore.Mvc.Internal.ActionMethodExecutor.SyncActionResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeActionMethodAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeNextActionFilterAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Rethrow(ActionExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeInnerFilterAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeNextExceptionFilterAsync()

到这里，log4net配置和全局异常捕捉就完成了。

需要注意的是，这里所谓的全局是指进入mvc中间件后产生的异常，如果在其他中间件中异常了，上面的方法是捕捉不到的，下面来模拟一下：

在 startup.cs 的 Configure 方法中 app.UserMvc(...) 之前添加如下代码

app.Use(async (context, next) =>
{
    if (context.Request.Path.Value.Contains("test"))
    {
        throw new Exception("中间件异常测试");
    }
    await next();
});

上面代码的作用是，当访问地址中带有 test 则抛出异常。

执行程序，访问  http://localhost:5000/test 会发现，程序报错，这时查看日志会发现，异常并没有被记录，也就是说，异常没有被我们的MvcGlobalExceptionFilter捕捉到，这显然不是我们想要的。

如果要捕捉到这种异常需要怎么处理呢？其实程序中已经给出了提示：

if (env.IsDevelopment())
{
    app.UseDeveloperExceptionPage();
}
else
{
    app.UseExceptionHandler("/Home/Error");
    app.UseHsts();
}

这是 startup.cs  Configure 中自动帮我们添加的代码，就是用于异常的捕获和处理，一种方式是对 /Home/Error 进行处理，在该action内记录异常，这种方法比较简单，这里就不详细说了。

接下来，我们用自定义中间件的方式来实现一下。

新建  GlobalExceptionMiddleware.cs 文件

using HZC.Core;
using HZC.Utils.Mvc;
using Microsoft.AspNetCore.Http;
using Newtonsoft.Json;
using System;
using System.Threading.Tasks;

namespace Taoxue.SchoolRoll.Website.Extensions
{
    public class GlobalExceptionMiddleWare
    {
        public readonly RequestDelegate Next;

        public GlobalExceptionMiddleWare(RequestDelegate next)
        {
            Next = next;
        }

        public async Task Invoke(HttpContext context)
        {
            try
            {
                await Next(context);
            }
            catch (Exception e)
            {
                context.Response.Clear();
                context.Response.StatusCode = StatusCodes.Status200OK;

                Log4NetUtil.LogError("全局异常", e);

                if (context.Request.IsAjax())
                {
                    context.Response.ContentType = ResponseContentTypes.Json;
                    await context.Response.WriteAsync(JsonConvert.SerializeObject(new { Code = 500, Message = e.Message }));
                }
                else
                {
                    context.Response.Redirect("/Home/Error");
                }
            }
        }
    }
}

建议在 Invoke 方法中 catch 代码块中再包一层 try..catch ，以防止处理代码发生错误时出现异常。

接下来，修改 startup.cs 的 Configure 方法，注释掉系统自带的异常处理代码，添加我们自定义的中间件

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    //if (env.IsDevelopment())
    //{
    //    app.UseDeveloperExceptionPage();
    //}
    //else
    //{
    //    app.UseExceptionHandler("/Home/Error");
    //    app.UseHsts();
    //}
    app.UseMiddleware();

    app.Use(async (context, next) =>
    {
        if (context.Request.Path.Value.Contains("test"))
        {
            throw new Exception("中间件异常测试");
        }
        await next();
    });

    app.UseHttpsRedirection();
    app.UseStaticFiles();

    app.UseMvc(routes =>
    {
        routes.MapRoute(
            name: "default",
            template: "{controller=Home}/{action=Index}/{id?}");
    });
}

再次执行程序，访问  http://localhost:5000/test 会发现我们定义的逻辑被执行，并且该异常也被记录到了日志文件中

＝＝＝＝＝＝＝＝＝＝
【日志级别】：ERROR
【记录时间】：2019-05-16 01:20:56,051 
【执行时间】：[7830]毫秒
【抛出信息】：全局异常 
【异常类型】：Exception 
【异常信息】：中间件异常测试 
【堆栈调用】：
   at Taoxue.SchoolRoll.Website.Startup.<>c.<b__5_0>d.MoveNext() in E:\项目\CSharp\xx\xxxx\Taoxue.SchoolRoll.Website\Startup.cs:line 77
--- End of stack trace from previous location where exception was thrown ---
   at Taoxue.SchoolRoll.Website.Extensions.GlobalExceptionMiddleWare.Invoke(HttpContext context) in E:\项目\CSharp\xx\xxxx\Taoxue.SchoolRoll.Website\Extensions\GlobalExceptionMiddleWare.cs:line 23