.NET MVC项目安装log4net 并进行异常处理

一.安装log4net并进行相应的配置

　　1.安装log4net

 　　2.在项目中添加log4net.config配置文件

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler,log4net-net-2.0"/>
  </configSections>
  <log4net>
    <root>
      <level value="ALL" />
      <appender-ref ref="LogFileAppender" />
      <!--<appender-ref ref="EventLogAppender" />-->
    </root>
    <!--定义输出到文件-->
    <appender name ="LogFileAppender" type="log4net.Appender.RollingFileAppender">
      <!--定义文件存放位置-->
      <param name="File" value ="App_Data"/>
      <param name="AppendToFile" value="true" />
      <param name="MaxSizeRollBackups" value="100" />
      <param name="MaxFileSize" value="10240" />
      <param name="StaticLogFileName" value="false" />
      <!--文件名格式-->
      <param name="DatePattern" value="yyyy.MM.dd'.txt'" />
      <param name="RollingStyle" value ="Date" />
      <!--不以独占方式记录日志,仅在记录每个日志的最短时间内锁定,因为部署到服务器上遇到了文件被占用无法下载日志-->
      <lockingModel type="log4net.Appender.FileAppender+MinimalLock" />
      <layout type="log4net.Layout.PatternLayout">
        <!--定义输出格式-->
        <!--示例 2018-08-20 12:10:49,348 -线程ID:[21] 日志级别:[INFO ] : [日志信息]-->
        <param name="ConversionPattern" value="%date 调用对象:[%logger ] 线程ID:[%thread] 日志级别:[%-5level] : [%message]%newline"/>
      
      </layout>
      <!--过滤级别 FATAL > ERROR > WARN > INFO > DEBUG-->
      <filter type="log4net.Filter.LevelRangeFilter">
        <param name="LevelMin" value="DEBUG" />
        <param name="LevelMax" value="FATAL" />
      </filter>
    </appender>
    <!--定义输出到 windows 事件中-->
    <appender name="EventLogAppender" type="log4net.Appender.EventLogAppender">
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline"></conversionPattern>
      </layout>
    </appender>
  </log4net>
</configuration>

　　3.在Global.asax的Application_Start中进行注册

log4net.Config.XmlConfigurator.Configure(new FileInfo(Server.MapPath("/log4net.config")));

　　4.编写LogHelper帮助类

public class LogHelper
    {
        private ILog _log4Net = null;
        private const string DEFAULT_LOGGER_NAME = "Logger";
        /// <summary>
        /// Prevents a default instance of the <see cref="LogWriter"/> class from being created.
        /// </summary>
        /// <param name="log4NetInstance">The log4net instance to be used.</param>
        private LogHelper(ILog log4NetInstance)
        {
            _log4Net = log4NetInstance;
        }

        /// <summary>
        /// Gets a logger with the specified configuration name.
        /// </summary>
        /// <param name="configName">Name of the logger in the configuration.</param>
        /// <returns>The logger obtained.</returns>
        /// <exception cref="System.Configuration.ConfigurationException">Thrown when no logger with the specified configuration name was found.</exception>
        public static LogHelper GetLogger(string configName)
        {
            var logger = LogManager.GetLogger(configName);
            if (logger == null)
            {
                throw new ArgumentException(string.Format("No logger configuration named '{0}' was found in the configuration.", configName), "configName");
            }
            return new LogHelper(logger);
        }

        /// <summary>
        /// Gets the default.
        /// </summary>
        public static LogHelper Default
        {
            get
            {
                return GetLogger(DEFAULT_LOGGER_NAME);
            }
        }

        /// <summary>
        /// Writes an information level logging message.
        /// </summary>
        /// <param name="message">The message to be written.</param>
        public void WriteInfo(object message)
        {
            _log4Net.Info(message);
        }

        /// <summary>
        /// Writes a warning level logging message.
        /// </summary>
        /// <param name="message">The message to be written.</param>
        public void WriteWarning(object message)
        {
            _log4Net.Warn(message);
        }

        /// <summary>
        /// Writes a warning level logging message.
        /// </summary>
        /// <param name="message">The message to be written.</param>
        /// <param name="exception">The exception.</param>
        public void WriteWarning(object message, System.Exception exception)
        {
            _log4Net.Warn(message, exception);
        }

        /// <summary>
        /// Writes the error.
        /// </summary>
        /// <param name="message">The message to be written.</param>
        public void WriteError(object message)
        {
            _log4Net.Error(message);
        }

        /// <summary>
        /// Writes the error level logging message..
        /// </summary>
        /// <param name="message">The message to be written.</param>
        /// <param name="exception">The exception.</param>
        public void WriteError(object message, System.Exception exception)
        {
            _log4Net.Error(message, exception);
        }

        /// <summary>
        /// Writes the fatal error level logging message..
        /// </summary>
        /// <param name="message">The message to be written.</param>
        public void WriteFatal(object message)
        {
            _log4Net.Fatal(message);
        }

        /// <summary>
        /// Writes the fatal error level logging message..
        /// </summary>
        /// <param name="message">The message to be written.</param>
        /// <param name="exception">The exception.</param>
        public void WriteFatal(object message, System.Exception exception)
        {
            _log4Net.Fatal(message, exception);
        }

        public void DeleteLog()
        {
            string logDirPath = Path.Combine(Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().Location), "Log");
            if (!Directory.Exists(logDirPath)) return;
            int days = 30;
            foreach (string filePath in Directory.GetFiles(logDirPath))
            {
                DateTime dt;
                DateTime.TryParse(Path.GetFileNameWithoutExtension(filePath).Replace(@"Log", "").Replace(".", "-"), out dt);
                if (dt.AddDays(days).CompareTo(DateTime.Now) < 0)
                {
                    File.Delete(filePath);
                }
            }
        }
    }

　　5.写入日志　

LogHelper.GetLogger(typeof(MyHandleErrorAttribute).ToString()).WriteError($"在相应{httpContext.Request.Url.AbsoluteUri}时出现异常!  异常信息:{filterContext.Exception.Message}");

二.自定义异常处理

　　1.通过重写HandleErrorAttribute中的OnException方法，来定制自己的异常处理

 public class MyHandleErrorAttribute:HandleErrorAttribute
    {
        public override void OnException(ExceptionContext filterContext)
        {
            var httpContext = filterContext.HttpContext;
            if (!filterContext.ExceptionHandled) //错误没有被别的HandleErrorAttribute处理
            {
                //日志记录
                LogHelper.GetLogger(typeof(MyHandleErrorAttribute).ToString()).WriteError($"在相应{httpContext.Request.Url.AbsoluteUri}时出现异常!  异常信息:{filterContext.Exception.Message}");
                filterContext.Result = new ViewResult() { ViewName= "/Views/Share/ErrorPage.cshtml" }; //返回指定的错误页
                filterContext.ExceptionHandled = true;
            }
        }
    }

　　2.全局注册上面编写的 MyHandleErrorAttribute

　　　　

//在App_Start里添加FilterConfig文件
  public class FilterConfig
    {
        public static void RegisterGlobalFilters(GlobalFilterCollection filters)
        {
            filters.Add(new MyHandleErrorAttribute());
        }
    }

//在Application_Start添加上面的配置
  protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();
            RouteConfig.RegisterRoutes(RouteTable.Routes);
            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
        }

三.用Application_Error实现异常处理

　　上面通过自定义的异常处理，存在一定的问题，有的异常可能拦截不到，例如路径输入错误等，不能进行异常的处理。通过Application_Error

可以对所有的异常进行拦截，但所有没有处理的错误都会导致这个Application_Error方法的执行，所以在这个方法中进行异常处理，能捕获到整个系统中没被处理的异常

　　//在Global.asax进行编写
    protected void Application_Error(object sender,EventArgs e)
        {
            Exception exception = Server.GetLastError();
            LogHelper.GetLogger(typeof(MvcApplication).ToString()).WriteError($"{Context.Request.Url.AbsoluteUri}出现错误，错误信息为:{exception}"); //进行日志记录
            Response.ContentType = "text/html";
            Response.Write("<h1>System Is Error</h1>");
            Server.ClearError();
        }