Aldığım yaklaşım, api denetleyici eylemlerinden istisnalar atmak ve istisnayı işleyen ve eylem yürütme bağlamında uygun bir yanıt ayarlayan bir istisna filtresine sahip olmaktır.
Filtre, filtreyi genel yapılandırmaya kaydetmeden önce belirli istisna türleri için işleyicileri kaydetmenin bir yolunu sağlayan akıcı bir arayüz sunar.
Bu filtrenin kullanımı, denetleyici eylemlerine yayılmak yerine merkezi istisna işlemeye olanak tanır. Bununla birlikte, denetleyici eylemi içinde istisnaları yakalayacağım ve söz konusu istisnanın işlenmesini merkezileştirmenin bir anlamı yoksa belirli bir yanıt döndüreceğim durumlar vardır.
Filtrenin örnek kaydı:
GlobalConfiguration.Configuration.Filters.Add(
new UnhandledExceptionFilterAttribute()
.Register<KeyNotFoundException>(HttpStatusCode.NotFound)
.Register<SecurityException>(HttpStatusCode.Forbidden)
.Register<SqlException>(
(exception, request) =>
{
var sqlException = exception as SqlException;
if (sqlException.Number > 50000)
{
var response = request.CreateResponse(HttpStatusCode.BadRequest);
response.ReasonPhrase = sqlException.Message.Replace(Environment.NewLine, String.Empty);
return response;
}
else
{
return request.CreateResponse(HttpStatusCode.InternalServerError);
}
}
)
);
UnhandledExceptionFilterAttribute sınıfı:
using System;
using System.Collections.Concurrent;
using System.Net;
using System.Net.Http;
using System.Text;
using System.Web.Http.Filters;
namespace Sample
{
/// <summary>
/// Represents the an attribute that provides a filter for unhandled exceptions.
/// </summary>
public class UnhandledExceptionFilterAttribute : ExceptionFilterAttribute
{
#region UnhandledExceptionFilterAttribute()
/// <summary>
/// Initializes a new instance of the <see cref="UnhandledExceptionFilterAttribute"/> class.
/// </summary>
public UnhandledExceptionFilterAttribute() : base()
{
}
#endregion
#region DefaultHandler
/// <summary>
/// Gets a delegate method that returns an <see cref="HttpResponseMessage"/>
/// that describes the supplied exception.
/// </summary>
/// <value>
/// A <see cref="Func{Exception, HttpRequestMessage, HttpResponseMessage}"/> delegate method that returns
/// an <see cref="HttpResponseMessage"/> that describes the supplied exception.
/// </value>
private static Func<Exception, HttpRequestMessage, HttpResponseMessage> DefaultHandler = (exception, request) =>
{
if(exception == null)
{
return null;
}
var response = request.CreateResponse<string>(
HttpStatusCode.InternalServerError, GetContentOf(exception)
);
response.ReasonPhrase = exception.Message.Replace(Environment.NewLine, String.Empty);
return response;
};
#endregion
#region GetContentOf
/// <summary>
/// Gets a delegate method that extracts information from the specified exception.
/// </summary>
/// <value>
/// A <see cref="Func{Exception, String}"/> delegate method that extracts information
/// from the specified exception.
/// </value>
private static Func<Exception, string> GetContentOf = (exception) =>
{
if (exception == null)
{
return String.Empty;
}
var result = new StringBuilder();
result.AppendLine(exception.Message);
result.AppendLine();
Exception innerException = exception.InnerException;
while (innerException != null)
{
result.AppendLine(innerException.Message);
result.AppendLine();
innerException = innerException.InnerException;
}
#if DEBUG
result.AppendLine(exception.StackTrace);
#endif
return result.ToString();
};
#endregion
#region Handlers
/// <summary>
/// Gets the exception handlers registered with this filter.
/// </summary>
/// <value>
/// A <see cref="ConcurrentDictionary{Type, Tuple}"/> collection that contains
/// the exception handlers registered with this filter.
/// </value>
protected ConcurrentDictionary<Type, Tuple<HttpStatusCode?, Func<Exception, HttpRequestMessage, HttpResponseMessage>>> Handlers
{
get
{
return _filterHandlers;
}
}
private readonly ConcurrentDictionary<Type, Tuple<HttpStatusCode?, Func<Exception, HttpRequestMessage, HttpResponseMessage>>> _filterHandlers = new ConcurrentDictionary<Type, Tuple<HttpStatusCode?, Func<Exception, HttpRequestMessage, HttpResponseMessage>>>();
#endregion
#region OnException(HttpActionExecutedContext actionExecutedContext)
/// <summary>
/// Raises the exception event.
/// </summary>
/// <param name="actionExecutedContext">The context for the action.</param>
public override void OnException(HttpActionExecutedContext actionExecutedContext)
{
if(actionExecutedContext == null || actionExecutedContext.Exception == null)
{
return;
}
var type = actionExecutedContext.Exception.GetType();
Tuple<HttpStatusCode?, Func<Exception, HttpRequestMessage, HttpResponseMessage>> registration = null;
if (this.Handlers.TryGetValue(type, out registration))
{
var statusCode = registration.Item1;
var handler = registration.Item2;
var response = handler(
actionExecutedContext.Exception.GetBaseException(),
actionExecutedContext.Request
);
// Use registered status code if available
if (statusCode.HasValue)
{
response.StatusCode = statusCode.Value;
}
actionExecutedContext.Response = response;
}
else
{
// If no exception handler registered for the exception type, fallback to default handler
actionExecutedContext.Response = DefaultHandler(
actionExecutedContext.Exception.GetBaseException(), actionExecutedContext.Request
);
}
}
#endregion
#region Register<TException>(HttpStatusCode statusCode)
/// <summary>
/// Registers an exception handler that returns the specified status code for exceptions of type <typeparamref name="TException"/>.
/// </summary>
/// <typeparam name="TException">The type of exception to register a handler for.</typeparam>
/// <param name="statusCode">The HTTP status code to return for exceptions of type <typeparamref name="TException"/>.</param>
/// <returns>
/// This <see cref="UnhandledExceptionFilterAttribute"/> after the exception handler has been added.
/// </returns>
public UnhandledExceptionFilterAttribute Register<TException>(HttpStatusCode statusCode)
where TException : Exception
{
var type = typeof(TException);
var item = new Tuple<HttpStatusCode?, Func<Exception, HttpRequestMessage, HttpResponseMessage>>(
statusCode, DefaultHandler
);
if (!this.Handlers.TryAdd(type, item))
{
Tuple<HttpStatusCode?, Func<Exception, HttpRequestMessage, HttpResponseMessage>> oldItem = null;
if (this.Handlers.TryRemove(type, out oldItem))
{
this.Handlers.TryAdd(type, item);
}
}
return this;
}
#endregion
#region Register<TException>(Func<Exception, HttpRequestMessage, HttpResponseMessage> handler)
/// <summary>
/// Registers the specified exception <paramref name="handler"/> for exceptions of type <typeparamref name="TException"/>.
/// </summary>
/// <typeparam name="TException">The type of exception to register the <paramref name="handler"/> for.</typeparam>
/// <param name="handler">The exception handler responsible for exceptions of type <typeparamref name="TException"/>.</param>
/// <returns>
/// This <see cref="UnhandledExceptionFilterAttribute"/> after the exception <paramref name="handler"/>
/// has been added.
/// </returns>
/// <exception cref="ArgumentNullException">The <paramref name="handler"/> is <see langword="null"/>.</exception>
public UnhandledExceptionFilterAttribute Register<TException>(Func<Exception, HttpRequestMessage, HttpResponseMessage> handler)
where TException : Exception
{
if(handler == null)
{
throw new ArgumentNullException("handler");
}
var type = typeof(TException);
var item = new Tuple<HttpStatusCode?, Func<Exception, HttpRequestMessage, HttpResponseMessage>>(
null, handler
);
if (!this.Handlers.TryAdd(type, item))
{
Tuple<HttpStatusCode?, Func<Exception, HttpRequestMessage, HttpResponseMessage>> oldItem = null;
if (this.Handlers.TryRemove(type, out oldItem))
{
this.Handlers.TryAdd(type, item);
}
}
return this;
}
#endregion
#region Unregister<TException>()
/// <summary>
/// Unregisters the exception handler for exceptions of type <typeparamref name="TException"/>.
/// </summary>
/// <typeparam name="TException">The type of exception to unregister handlers for.</typeparam>
/// <returns>
/// This <see cref="UnhandledExceptionFilterAttribute"/> after the exception handler
/// for exceptions of type <typeparamref name="TException"/> has been removed.
/// </returns>
public UnhandledExceptionFilterAttribute Unregister<TException>()
where TException : Exception
{
Tuple<HttpStatusCode?, Func<Exception, HttpRequestMessage, HttpResponseMessage>> item = null;
this.Handlers.TryRemove(typeof(TException), out item);
return this;
}
#endregion
}
}
Kaynak kodu da burada bulunabilir .