WebAPI异常捕捉处理，结合log4net日志（webapi框架）

一：异常捕捉处理

首先，在我们需要区分controller的类型。是全部基层controller,还是Apicontroller。（当然一般API框架，用的都是Apicontroller）。两者异常处理是不同的。

1.apicontroller  webapi框架错误处理：

首先在App_Start里添加一个新类，继承于ExceptionFilterAttribute类

public class WebApiExceptionFilterAttribute : ExceptionFilterAttribute
{
      //重写基类的异常处理方法
        #region
        public override void OnException(HttpActionExecutedContext actionExecutedContext)
        {

            //2.返回调用方具体的异常信息
            if (actionExecutedContext.Exception is NotImplementedException)
            {
                var oResponse = new HttpResponseMessage(HttpStatusCode.NotImplemented);
                //oResponse.Content = new StringContent("方法不被支持");
                oResponse.Content = new StringContent(actionExecutedContext.Exception.Message);
                oResponse.ReasonPhrase = "This Func is Not Supported";
                actionExecutedContext.Response = oResponse;
            }
            else if (actionExecutedContext.Exception is TimeoutException)
            {
                actionExecutedContext.Response = new HttpResponseMessage(HttpStatusCode.RequestTimeout);
            }
            //.....这里可以根据项目需要返回到客户端特定的状态码。如果找不到相应的异常，统一返回服务端错误500
            else
            {
                // actionExecutedContext.Response = new HttpResponseMessage(HttpStatusCode.InternalServerError);

                //注释掉错误信息的展示，显示统一的错误
                var Message = JsonHelper.GetJsonString(new { Errorcode = HttpStatusCode.InternalServerError, message = actionExecutedContext.Exception.Message});
                //写日志
                ILog log = LogManager.GetLogger(typeof(GoodsController));
                log.Error(Message, new Exception("Error异常"));

                // 自定义message的错误信息
                //var Message =JsonHelper.GetJsonString(new {Errorcode = HttpStatusCode.InternalServerError, message = "接口调用失败，请检查传入参数是否正确"});

                var oResponse = new HttpResponseMessage(HttpStatusCode.InternalServerError)
                {
                  //Content = new StringContent(actionExecutedContext.Exception.Message),
                  Content = new StringContent(Message),
                  ReasonPhrase = "Error"
                };
                actionExecutedContext.Response = oResponse;
            }

            base.OnException(actionExecutedContext);
        }
        #endregion

}

看个人需求是全局捕捉错误，还是区域捕捉。

全局：Global里加上这句。GlobalConfiguration.Configuration.Filters.Add(new WebApiExceptionFilterAttribute());

区域： 这ApiController或是方法名称前加一个特性就OK了。

2.继承controller的 还是MVC那一套（在Global中添加 Application_Error方法）

protected void Application_Error(object sender, EventArgs e)
        {
            // 在出现未处理的错误时运行的代码
            HttpContext ctx = HttpContext.Current;
            Exception exception = ctx.Server.GetLastError();
            Exception exception_s = Server.GetLastError();
            HttpException ex = exception_s as HttpException;
            if (exception != null)
            {
                string m = exception.Message;
                string errorInfo = "URL:<strong>" + ctx.Request.RawUrl.ToString() + "<strong><br/>Source:<strong>" + exception.Source
                                   + "<strong><br/>Message:<strong>" + exception.Message + "<>";
                if (!m.Contains("不存在"))
                {
                    if (exception.InnerException != null)
                        errorInfo += "<br/>错误信息为:<strong>" + exception.InnerException.Message + "<>";
                }
                if (exception is HttpException)
                {
                    HttpException ex2 = exception as HttpException;
                    int httpCode = ex2.GetHttpCode();
                    errorInfo += "<br />Code:<strong>" + httpCode.ToString() + "<>";
                }

                //写日志
                ILog log = LogManager.GetLogger(typeof(GoodsController));
                log.Error(errorInfo, new Exception("Error异常")); ctx.Items.Add("LastError", errorInfo); ctx.Server.ClearError(); 
                } 

               try { //写逻辑 ctx.Response.Redirect("/Home/Index"); } catch { }
                }

二：log4net日志管理。配合WebApi框架，个人感觉十分方便

打开NuGet，添加log4net。成功之后，可以直接处理

使用方法：

 [HttpGet,Route("LogTest")]
        public IHttpActionResult LogTest()
        {
            ILog log = LogManager.GetLogger(typeof(GoodsController)); // 下面是日志处理
            log.Debug("测试debug", new Exception("debug异常"));
            log.Info("测试Info", new Exception("Info异常"));
            log.Warn("测试Warn", new Exception("Warn异常"));

            log.Error("测试Error", new Exception("Error异常"));
            log.Fatal("测试Fatal", new Exception("Fatal异常"));
            return Json(new {result = "Complent"});
        }

log4net需要配置文件，才能输出。添加Log4net.config文件。然后在程序集AssemblyInfo.cs中，添加 [assembly: XmlConfigurator(Watch = true, ConfigFile = "Log4Net.config")]

<?xml version="1.0" encoding="utf-8"?>
<configuration>

  <log4net>
    <!--记录所有的完整日志-->
    <appender name="AllLogFileAppender" type="log4net.Appender.RollingFileAppender">
      <!--或者是文件名或是文件夹（没有后缀）Gets or sets the path to the file that logging will be written to.，-->
      <file value="log/all/log_" />
      <!--是否总是写在一个文件里Gets or sets a value indicating whether to always log to the same file.-->
      <staticLogFileName value="false" />
      <!--Gets or sets a flag that indicates whether the file should be appended to or overwritten.-->
      <appendToFile value="true" />
      <!--可设置为Size、Date，即大小/日期超出一定范围后就新建一个日志文件-->
      <rollingStyle value="Date" />
      <!--一天最多保存多少Gets or sets the maximum number of backup files that are kept before the oldest is erased.-->
      <maxSizeRollBackups value="" />
      <!--每个文件最大大小,单位可是MB,KBGets or sets the maximum size that the output file is allowed to reach before being rolled over to backup files.-->
      <maximumFileSize value="5MB" />
      <!--设置用来生产文件的日期格式Gets or sets the date pattern to be used for generating file names when rolling over on date.-->
      <datePattern value="yyyy-MM-dd'.log'"/>
      <!--日志输入的通用格式（日志的内容格式）-->
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline" />
      </layout>
      <filter type="log4net.Filter.LevelRangeFilter,log4net">
        <!--级别由低往高依次是
        ALL
        DEBUG
        INFO
        WARN
        ERROR
        FATAL
        None-->
        <levelMin value="DEBUG" />
        <levelMax value="Warn" />
      </filter>
    </appender>

    <!--记录错误日志，这些错误往往是一个程序bug或是要注意的-->
    <appender name="ErrorLogFileAppender" type="log4net.Appender.RollingFileAppender">
      <!--或者是文件名或是文件夹（没有后缀）Gets or sets the path to the file that logging will be written to.，-->
      <file value="log/error/error_" />
      <!--是否总是写在一个文件里Gets or sets a value indicating whether to always log to the same file.-->
      <staticLogFileName value="false" />
      <!--Gets or sets a flag that indicates whether the file should be appended to or overwritten.-->
      <appendToFile value="true" />
      <!--可设置为Size、Date，即大小/日期超出一定范围后就新建一个日志文件-->
      <rollingStyle value="Date" />
      <!--一天最多保存多少Gets or sets the maximum number of backup files that are kept before the oldest is erased.-->
      <maxSizeRollBackups value="" />
      <!--每个文件最大大小,单位可是MB,KBGets or sets the maximum size that the output file is allowed to reach before being rolled over to backup files.-->
      <maximumFileSize value="5MB" />
      <!--设置用来生产文件的日期格式Gets or sets the date pattern to be used for generating file names when rolling over on date.-->
      <datePattern value="yyyy-MM-dd'.log'"/>
      <!--日志输入的通用格式（日志的内容格式）-->
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline" />
      </layout>
      <filter type="log4net.Filter.LevelRangeFilter,log4net">
        <levelMin value="ERROR" />
        <levelMax value="FATAL" />
      </filter>
    </appender>
    <!--Set root logger level to DEBUG and its only appender to A1-->
    <root>
      <!--控制级别，由低到高: ALL|DEBUG|INFO|WARN|ERROR|FATAL|OFF-->
      <level value="ALL" />
      <appender-ref ref="AllLogFileAppender" />
      <appender-ref ref="ErrorLogFileAppender" />
    </root>
  </log4net>
  <system.web>
      <compilation debug="true" targetFramework="4.5.2" />
      <httpRuntime targetFramework="4.5.2" />
    </system.web>

</configuration>

上面只是写了一个，测试方法而已。WebAPI实际使用本文全局错误处理 + log4net，日志模块简直起飞。遇到问题，系统BUG之类的也不用慌，去日志里找就行了，全都记录了。