Asp.net mvc 笔记

捕捉处理全局异常

自定义异常处理类如LogErrorAttribute继承HandleErrorAttribute并重写OnException实现处理逻辑
将LogErrorAttribute加入启动时的Filter注册使之在管道中生效
在需要捕捉异常的Controller、Action上使用它

自定义异常处理类

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using NLog;
using EmpowerApiService.Entity;
using Newtonsoft.Json;

namespace EmpowerApiService.Filter
{
    public class LogErrorAttribute : HandleErrorAttribute
    {
        private static NLog.Logger logger = NLog.LogManager.GetCurrentClassLogger();

        public override void OnException(ExceptionContext filterContext)
        {
            // 如果发现被处理过，则不进行处理
            if (filterContext.ExceptionHandled) { return; }

            // 可获取一些关键参数待用
            var controllerName = (string)filterContext.RouteData.Values["controller"];
            var actionName = (string)filterContext.RouteData.Values["action"];

            // 将http上下文关键信息写入日志
            if (filterContext.HttpContext != null && filterContext.HttpContext.Request != null)
            {
                var requestUrl = filterContext.HttpContext.Request.Url.ToString();
                var requestParams = filterContext.HttpContext.Request.Params;
                var requestParamsStr = HttpUtility.UrlDecode(requestParams.ToString());

                // 写日志
                logger.Error(
                    filterContext.Exception,
                    "url: {0}, params: {1}",
                    new Object[] { requestUrl, requestParamsStr });
            }

            // build http response result
            filterContext.Result = new JsonResult
            {
                ContentType = "applicaltion/json",
                ContentEncoding = System.Text.Encoding.UTF8,
                Data = BuildErrorData(filterContext.Exception),
                JsonRequestBehavior = JsonRequestBehavior.AllowGet
            };

            filterContext.ExceptionHandled = true;
        }

        private object BuildErrorData(Exception error)
        {
            if(error == null) { return null; }

            var ar = new AjaxResult();

            if (error is ArgumentException)
            {
                ar.Code = AjaxResult.Err_Code_BadRequest;
                ar.Message = error.Message;
            }
            else if (error is System.Runtime.InteropServices.COMException)
            {
                ar.Code = AjaxResult.Err_Code_InternalServer;
                try
                {
                    ar.Message = EmpowerUtils.EmpowerProject.TkErrorDescription(error.HResult);
                }
                catch
                {
                    ar.Message = "Toolkit error";
                }
            }
            else
            {
                ar.Code = AjaxResult.Err_Code_InternalServer;
                ar.Message = error.Message ?? AjaxResult.Err_Msg_InternalServer;
            }

            ar.Data = error.HResult.ToString("X");
            return ar;
        }
    }
}

关于自定义响应结果，需要注意的两点：

修改HttpContext.Response.StatusCode，asp.net mvc 将根据响应码自动匹配并返回对应的错误信息页面，如下图

设置ExceptionContext.Result，可返回自定义的ActionResult类型的结果，比如一个Json结构的错误消息，如下图
HttpContext.Response.StatusCode与 ExceptionContext.Result会冲突，不能同时设置这两个属性，或者说修改了StatusCode后，Result将不再起作用。

注册LogErrorAttribute

注册自定义的处理类，使之生效，替换默认的错误处理，修改APP_Start中的FilterConfig.cs

namespace EmpowerApiService
{
    public class FilterConfig
    {
        public static void RegisterGlobalFilters(GlobalFilterCollection filters)
        {
            //filters.Add(new HandleErrorAttribute());
            filters.Add(new EmpowerApiService.Filter.LogErrorAttribute());
        }
    }
}

使用[LogError]特性

在需要使用错误处理的Controller或Action上使用特性，就可以捕捉并处理异常

using EmpowerApiService.Filter;

namespace EmpowerApiService.Controllers{

   [LogError]
   public class xxxController : Controller 
   { ... }
}

使用日志组件 NLog

先从Nuget安装NLog，网文说要同时安装NLog.Config，经实测不安装也可以，测试版本是5.2.3
右键点击目标项目，新增项，选择新增配置文件，起名NLog.config

编辑文件如下

<?xml version="1.0"?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
	  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	  xsi:schemaLocation="http://www.nlog-project.org/schemas/NLog.xsd"
	  autoReload="true"
	  throwException="false"
	  internalLogLevel="Off" internalLogFile="c:\temp\nlog-internal.log">

	<variable name="appName" value="EmpowerApiService" />
	
	<targets>
		<target name="logfile" 
				xsi:type="File"
				fileName="${basedir}/logs/${appName}-${shortdate}.log"
				layout="${longdate}|${uppercase:${level}}|${message}${newline}${callsite}(${callsite-filename:includeSourcePath=False}:${callsite-linenumber})|${exception:format=ToString}"
				maxArchiveFiles="999"
				archiveFileName="${basedir}/logs/${appName}-${shortdate}-${###}.log"
				createDirs="true"
				archiveAboveSize="5242880"
				archiveEvery="Day"
				archiveNumbering="Sequence"
				encoding="UTF-8"
				>
		</target>
	</targets>

	<rules>
		<logger name="*" minlevel="Debug" writeTo="logfile"/>
	</rules>
</nlog>