Skip to content

IharYakimush/asp-net-core-exception-handling

Folders and files

NameName
Last commit message
Last commit date

Latest commit

 

History

53 Commits
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Repository files navigation

ASP.NET Core Exception Handling Middleware

ASP.NET Core exception handling policies middleware. Allows to set a chain of exception handlers per exception type. OOTB handlers: log, retry, set responce headers and body

Code Sample

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc();

    services.AddExceptionHandlingPolicies(options =>
    {
        options.For<InitializationException>().Rethrow();
                
        options.For<SomeTransientException>().Retry(ro => ro.MaxRetryCount = 2).NextPolicy();
                
        options.For<SomeBadRequestException>()
            .Response(e => 400)
                .Headers((h, e) => h["X-MyCustomHeader"] = e.Message)
				.WithBody((req,sw, exception) =>
                    {
                        byte[] array = Encoding.UTF8.GetBytes(exception.ToString());
                        return sw.WriteAsync(array, 0, array.Length);
                    })
            .NextPolicy();

        // Ensure that all exception types are handled by adding handler for generic exception at the end.
        options.For<Exception>()
            .Log(lo =>
                {
                    lo.LogAction = (l, c, e) => l.LogError(e,"UnhandledException");
                    lo.Category = (context, exception) => "MyCategory";
                })
            .Response(null, ResponseAlreadyStartedBehaviour.GoToNextHandler)
                .ClearCacheHeaders()
                .WithObjectResult((r, e) => new { msg = e.Message, path = r.Path })
            .Handled();
    });
}

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    app.UseExceptionHandlingPolicies();
    app.UseMvc();
}

Policy exception handler transitions

When exception catched in middleware it try to apply handlers from first registered policy suitable for given exception. Policy contains a chain of handlers. Each handler perform some action and apply transition. To prevent re throw of exception handlers chain MUST ends with "Handled" transition. Following handlers currently supported:

Handler Action Transition
Rethrow Apply ReThrow transition ReThrow
NextPolicy Try to execute next policy suitable for given exception NextPolicy
Handled Mark exception as handled to prevent it from bein re thrown Handled
Retry Execute aspnetcore pipeline again if retry count not exceed limit Retry (if retry limit not exceeded) or NextHandler
Log Log exception NextHandler
DisableFurtherLog Prevent exception from being logged again in current middleware (for current request only) NextHandler
Response Modify response (set status code, headers and body) depending on further response builder configuration NextHandler

Sample of transitions: alt text

Nuget

Package Comments
Community.AspNetCore.ExceptionHandling Main functionality
Community.AspNetCore.ExceptionHandling.Mvc Allow to use MVC IActionResult (including ObjectResult) in 'Response' handler
Community.AspNetCore.ExceptionHandling.NewtonsoftJson Allow to set Json serialized object as a response body in 'Response' handler. Use it only if 'Community.AspNetCore.ExceptionHandling.Mvc' usage not possible