ASP.NET MVC 异常Exception拦截

一、前言

由于客户端的环境不一致，有可能会造成我们预计不到的异常错误，所以在项目中，友好的异常信息提示，是非常重要的。在asp.net mvc中实现异常属性拦截也非常简单，只需要继承另一个类(System.Web.Mvc.FilterAttribute)和一个接口(System.Web.Mvc.IExceptionFilter)，实现接口里面OnException方法，或者直接继承Mvc 提供的类System.Web.Mvc.HandleErrorAttribute。

二、实现关键逻辑

继承System.Web.Mvc.HandleErrorAttribute，重写了OnException方法，主要实现逻辑代码如下：

1. public class HandlerErrorAttribute : HandleErrorAttribute
2. {
3.     /// <summary>
4.     /// 控制器方法中出现异常，会调用该方法捕获异常
5.     /// </summary>
6.     /// <param name="context">提供使用</param>
7.     public override void OnException(ExceptionContext context)
8.     {
9.         WriteLog(context);
10.         base.OnException(context);
11.         context.ExceptionHandled = true;
12.         if (context.Exception is UserFriendlyException)
13.         {
14.             context.HttpContext.Response.StatusCode = (int)HttpStatusCode.OK;
15.             context.Result = new ContentResult { Content = new AjaxResult { type = ResultType.error, message = context.Exception.Message }.ToJson() };
16.         }
17.         else if (context.Exception is NoAuthorizeException)
18.         {
19.             context.HttpContext.Response.StatusCode = (int)HttpStatusCode.Unauthorized;
20.             if (!context.HttpContext.Request.IsAjaxRequest())
21.             {
22.                 context.HttpContext.Response.RedirectToRoute("Default", new { controller = "Error", action = "Error401", errorUrl = context.HttpContext.Request.RawUrl });
23.             }
24.             else
25.             {
26.                 context.Result = new ContentResult { Content = context.HttpContext.Request.RawUrl };
27.             }
28.         }
29.         else
30.         {
31.              context.HttpContext.Response.StatusCode = (int)HttpStatusCode.InternalServerError;
32.              ExceptionMessage error = new ExceptionMessage(context.Exception);
33.              var s = error.ToJson();
34.              if (!context.HttpContext.Request.IsAjaxRequest())
35.              {
36.                  context.HttpContext.Response.RedirectToRoute("Default", new { controller = "Error", action = "Error500", data = WebHelper.UrlEncode(s) });
37.              }
38.              else
39.              {
40.                  context.Result = new ContentResult { Content = WebHelper.UrlEncode(s) };
41.              }
42.         }
43.     }
44.  
45.     /// <summary>
46.     /// 写入日志（log4net）
47.     /// </summary>
48.     /// <param name="context">提供使用</param>
49.     private void WriteLog(ExceptionContext context)
50.     {
51.         if (context == null)
52.             return;
53.         if (context.Exception is NoAuthorizeException || context.Exception is UserFriendlyException)
54.         {
55.             //友好错误提示,未授权错误提示，记录警告日志
56.             LogHelper.Warn(context.Exception.Message);
57.         }
58.         else
59.         {
60.             //异常错误，
61.             LogHelper.Error(context.Exception);
62.  
63.             ////TODO :写入错误日志到数据库
64.         }
65.     }
66. }

MVC 过滤器全局注册异常拦截:

1. public class FilterConfig
2.     {
3.         public static void RegisterGlobalFilters(GlobalFilterCollection filters)
4.         {
5.             filters.Add(new HandlerErrorAttribute());
6.         }
7.     }

我们看到，context.Exception 分为3种：UserFriendlyException，NoAuthorizeException 或 Exception；UserFriendlyException 是指友好异常，前端友好提示错误信息。NoAuthorizeException 为401未授权异常，当页面未被授权访问时，返回该异常，并携带有未授权的路径地址。其他异常统一返回500错误，并携带异常信息。

三、异常处理

1.401 未授权错误

异常定义代码：

1. /// <summary>
2. /// 没有被授权的异常
3. /// </summary>
4. public class NoAuthorizeException : Exception
5. {
6.     public NoAuthorizeException(string message)
7.         : base(message)
8.     {
9.     }
10. }

抛出异常代码：

1. throw new NoAuthorizeException("未授权");

前端UI效果：

2.404 未找到页面错误

MVC的404异常处理，有几种方式，我们采用了在Global.asax全局请求函数中处理, 请查看以下代码

1. protected void Application_EndRequest()
2.      {
3.          if (Context.Response.StatusCode == 404)
4.          {
5.              bool isAjax = new HttpRequestWrapper(Context.Request).IsAjaxRequest();
6.              if (isAjax)
7.              {
8.                  Response.Clear();
9.                  Response.Write(Context.Request.RawUrl);
10.              }
11.              else
12.              {
13.                  Response.RedirectToRoute("Default", new { controller = "Error", action = "Error404", errorUrl = Context.Request.RawUrl });
14.              }
15.          }
16.      }

前端UI效果:

3.500服务器内部错误

500异常错误抛出的异常信息对象定义:

1. /// <summary>
2. /// 异常错误信息
3. /// </summary>
4. [Serializable]
5. public class ExceptionMessage
6. {
7.     public ExceptionMessage()
8.     {
9.     }
10.  
11.     /// <summary>
12.     /// 构造函数
13.     /// 默认显示异常页面
14.     /// </summary>
15.     /// <param name="ex">异常对象</param>
16.     public ExceptionMessage(Exception ex)
17.         :this(ex, true)
18.     {
19.  
20.     }
21.     /// <summary>
22.     /// 构造函数
23.     /// </summary>
24.     /// <param name="ex">异常对象</param>
25.     /// <param name="isShowException">是否显示异常页面</param>
26.     public ExceptionMessage(Exception ex, bool isShowException)
27.     {
28.         MsgType = ex.GetType().Name;
29.         Message = ex.InnerException != null ? ex.InnerException.Message : ex.Message;
30.         StackTrace = ex.StackTrace.Length > 300 ? ex.StackTrace.Substring(0, 300) : ex.StackTrace;
31.         Source = ex.Source;
32.         Time = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss");
33.         Assembly = ex.TargetSite.Module.Assembly.FullName;
34.         Method = ex.TargetSite.Name;
35.  
36.         ShowException = isShowException;
37.         var request = HttpContext.Current.Request;
38.         IP = Net.Ip;
39.         UserAgent = request.UserAgent;
40.         Path = request.Path;
41.         HttpMethod = request.HttpMethod;
42.     }
43.     /// <summary>
44.     /// 消息类型
45.     /// </summary>
46.     public string MsgType { get; set; }
47.  
48.     /// <summary>
49.     /// 消息内容
50.     /// </summary>
51.     public string Message { get; set; }
52.  
53.     /// <summary>
54.     /// 请求路径
55.     /// </summary>
56.     public string Path { get; set; }
57.  
58.     /// <summary>
59.     /// 程序集名称
60.     /// </summary>
61.     public string Assembly { get; set; }
62.  
63.     /// <summary>
64.     /// 异常参数
65.     /// </summary>
66.     public string ActionArguments { get; set; }
67.  
68.     /// <summary>
69.     /// 请求类型
70.     /// </summary>
71.     public string HttpMethod { get; set; }
72.  
73.     /// <summary>
74.     /// 异常堆栈
75.     /// </summary>
76.     public string StackTrace { get; set; }
77.  
78.     /// <summary>
79.     /// 异常源
80.     /// </summary>
81.     public string Source { get; set; }
82.  
83.     /// <summary>
84.     /// 服务器IP 端口
85.     /// </summary>
86.     public string IP { get; set; }
87.  
88.     /// <summary>
89.     /// 客户端浏览器标识
90.     /// </summary>
91.     public string UserAgent { get; set; }
92.  
93.  
94.     /// <summary>
95.     /// 是否显示异常界面
96.     /// </summary>
97.     public bool ShowException { get; set; }
98.  
99.     /// <summary>
100.     /// 异常发生时间
101.     /// </summary>
102.     public string Time { get; set; }
103.  
104.     /// <summary>
105.     /// 异常发生方法
106.     /// </summary>
107.     public string Method { get; set; }
108. }

抛出异常代码：

1. throw new Exception("出错了");

前端UI效果：

4. UserFriendlyException 友好异常

异常定义代码：

1. /// <summary>
2. /// 用户友好异常
3. /// </summary>
4. public class UserFriendlyException : Exception
5. {
6.     public UserFriendlyException(string message)
7.         : base(message)
8.     {
9.     }
10. }

在异常拦截关键代码中，我们发现友好异常（UserFriendlyException）其实是返回了一个结果对象AjaxResult，

AjaxResult对象的定义：

1. /// <summary>
2.     /// 表示Ajax操作结果
3.     /// </summary>
4.     public class AjaxResult
5.     {
6.         /// <summary>
7.         /// 获取 Ajax操作结果类型
8.         /// </summary>
9.         public ResultType type { get; set; }
10.  
11.         /// <summary>
12.         /// 获取 Ajax操作结果编码
13.         /// </summary>
14.         public int errorcode { get; set; }
15.  
16.         /// <summary>
17.         /// 获取 消息内容
18.         /// </summary>
19.         public string message { get; set; }
20.  
21.         /// <summary>
22.         /// 获取 返回数据
23.         /// </summary>
24.         public object resultdata { get; set; }
25.     }
26.     /// <summary>
27.     /// 表示 ajax 操作结果类型的枚举
28.     /// </summary>
29.     public enum ResultType
30.     {
31.         /// <summary>
32.         /// 消息结果类型
33.         /// </summary>
34.         info = 0,
35.  
36.         /// <summary>
37.         /// 成功结果类型
38.         /// </summary>
39.         success = 1,
40.  
41.         /// <summary>
42.         /// 警告结果类型
43.         /// </summary>
44.         warning = 2,
45.  
46.         /// <summary>
47.         /// 异常结果类型
48.         /// </summary>
49.         error = 3
50.     }

四、Ajax请求异常时处理

在异常拦截的关键代码中，我们有看到，如果是ajax请求时，是执行不同的逻辑，这是因为ajax的请求，不能直接通过MVC的路由跳转，在请求时必须返回结果内容

然后在前端ajax的方法中，统一处理返回的错误，以下是我们项目中用到的ajax封装，对异常错误，进行了统一处理。

1. (function ($) {
2.     "use strict";
3.  
4.     $.httpCode = {
5.         success: "1",
6.         fail: "3",
7.     };
8.     // http 通信异常的时候调用此方法
9.     $.httpErrorLog = function (msg) {
10.         console.log('=====>' + new Date().getTime() + '<=====');
11.         console.log(msg);
12.     };
13.  
14.     // ajax请求错误处理
15.     $.httpError = function (xhr, textStatus, errorThrown) {
16.  
17.         if (xhr.status == 401) {
18.             location.href = "/Error/Error401?errorUrl=" + xhr.responseText;
19.         }
20.  
21.         if (xhr.status == 404) {
22.             location.href = "/Error/Error404?errorUrl=" + xhr.responseText;
23.         }
24.  
25.         if (xhr.status == 500) {
26.             location.href = "/Error/Error500?data=" + xhr.responseText;
27.         }
28.     };
29.  
30.     /* get请求方法（异步）:
31.     * url地址, param参数, callback回调函数 beforeSend 请求之前回调函数, complete 请求完成之后回调函数
32.     * 考虑到get请求一般将参数与url拼接一起传递，所以将param参数放置最后
33.     * 返回AjaxResult结果对象
34.     */
35.     $.httpAsyncGet = function (url, callback, beforeSend, complete, param) {
36.         $.ajax({
37.             url: url,
38.             data: param,
39.             type: "GET",
40.             dataType: "json",
41.             async: true,
42.             cache: false,
43.             success: function (data) {
44.                 if ($.isFunction(callback)) callback(data);
45.             },
46.             error: function (XMLHttpRequest, textStatus, errorThrown) {
47.                 $.httpError(XMLHttpRequest, textStatus, errorThrown);
48.             },
49.             beforeSend: function () {
50.                 if (!!beforeSend) beforeSend();
51.             },
52.             complete: function () {
53.                 if (!!complete) complete();
54.             }
55.         });
56.     };
57.  
58.     /* get请求方法（同步）:
59.     * url地址,param参数
60.     * 返回实体数据对象
61.     */
62.     $.httpGet = function (url, param) {
63.         var res = {};
64.         $.ajax({
65.             url: url,
66.             data: param,
67.             type: "GET",
68.             dataType: "json",
69.             async: false,
70.             cache: false,
71.             success: function (data) {
72.                 res = data;
73.             },
74.             error: function (XMLHttpRequest, textStatus, errorThrown) {
75.                 $.httpError(XMLHttpRequest, textStatus, errorThrown);
76.             },
77.         });
78.         return res;
79.     };
80.  
81.     /* post请求方法（异步）:
82.     * url地址, param参数, callback回调函数 beforeSend 请求之前回调函数, complete 请求完成之后回调函数
83.     * 返回AjaxResult结果对象
84.     */
85.     $.httpAsyncPost = function (url, param, callback, beforeSend, complete) {
86.         $.ajax({
87.             url: url,
88.             data: param,
89.             type: "POST",
90.             dataType: "json",
91.             async: true,
92.             cache: false,
93.             success: function (data) {
94.                 if ($.isFunction(callback)) callback(data);
95.             },
96.             error: function (XMLHttpRequest, textStatus, errorThrown) {
97.                 $.httpError(XMLHttpRequest, textStatus, errorThrown);
98.             },
99.             beforeSend: function () {
100.                 if (!!beforeSend) beforeSend();
101.             },
102.             complete: function () {
103.                 if (!!complete) complete();
104.             }
105.         });
106.     };
107.  
108.     /* post请求方法（同步）:
109.     * url地址,param参数, callback回调函数
110.     * 返回实体数据对象
111.     */
112.     $.httpPost = function (url, param, callback) {
113.         $.ajax({
114.             url: url,
115.             data: param,
116.             type: "POST",
117.             dataType: "json",
118.             async: false,
119.             cache: false,
120.             success: function (data) {
121.                 if ($.isFunction(callback)) callback(data);
122.             },
123.             error: function (XMLHttpRequest, textStatus, errorThrown) {
124.                 $.httpError(XMLHttpRequest, textStatus, errorThrown);
125.             },
126.         });
127.     },
128.  
129.     /* ajax异步封装:
130.     * type 请求类型, url地址, param参数, callback回调函数
131.     * 返回实体数据对象
132.     */
133.     $.httpAsync = function (type, url, param, callback) {
134.         $.ajax({
135.             url: url,
136.             data: param,
137.             type: type,
138.             dataType: "json",
139.             async: true,
140.             cache: false,
141.             success: function (data) {
142.                 if ($.isFunction(callback)) callback(data);
143.             },
144.             error: function (XMLHttpRequest, textStatus, errorThrown) {
145.                 $.httpError(XMLHttpRequest, textStatus, errorThrown);
146.             },
147.         });
148.     };
149. })(jQuery);

五、总结

至此，我们发现其实MVC的异常处理，真的很简单，只需要在过滤器中全局注册之后，然后重写OnException的方法，实现逻辑即可。关键是在于项目中Ajax请求，需要用统一的封装方法。