Question

假设我有一个构造函数，由于我无法控制的原因，它的初始化可能会引发异常。

FantasticApiController(IAwesomeGenerator awesome,
    IBusinessRepository repository, IIceCreamFactory factory)
{
       Awesome = awesome;
       Repository = repository;
       IceCream = factory.MakeIceCream();

       DoSomeInitialization(); // this can throw an exception
}

通常，当WebAPI中的Controller操作抛出异常时，我可以通过csutom ExceptionFilterAttribute处理它：

public class CustomErrorHandler
{
    public override void OnException(HttpActionExecutedContext context)
    {
        // Critical error, this is real bad.
        if (context.Exception is BubonicPlagueException)
        {
            Log.Error(context.Exception, "CLOSE EVERYTHING!");
            Madagascar.ShutdownAllPorts();
        }

        // No big deal, just show something user friendly
        throw new HttpResponseException(new HttpResponseMessage
        {
            Content = new StringContent("Hey something bad happened. " +
                                        "Not closing the ports though"),
            StatusCode = HttpStatusCode.InternalServerError;
        });
    }

因此，如果我有一个BoardPlane API方法会抛出BubonicPlagueException，那么我的CustomerErrorHandler将关闭到马达加斯加的端口，并按预期将其记录为错误。在其他情况下，当它不是很严重时，我只会显示一些用户友好的消息并返回500 InternalServerError。

但是在DoSomeInitialization抛出异常的情况下，这绝对没有任何意义。 如何在WebAPI控制器构造函数中处理异常？

Answer 1

创建WebApi控制器，从而通过HttpControllerActivators调用构造函数。默认激活器是System.Web.Http.Dispatcher.DefaultHttpControllerActivator。

选项1＆amp;的非常粗略的例子2在github上https://github.com/markyjones/StackOverflow/tree/master/ControllerExceptionHandling/src

选项1 非常适用于使用DI容器（您可能已经使用了一个）。我已经使用Ninject作为我的示例，并使用“拦截器”Read More拦截并尝试/捕获对DefaultHttpControllerActivator上的Create方法的调用。我知道至少AutoFac和Ninject可以做以下事情：

创建拦截器

我不知道您的马达加斯加和日志物品的生命范围是什么，但它们很可能被注入您的拦截器

public class ControllerCreationInterceptor : Ninject.Extensions.Interception.IInterceptor
{
    private ILog _log;
    private IMadagascar _madagascar;

    public ControllerCreationInterceptor(ILog log, IMadagascar madagascar)
    {
        _log = log;
        _madagascar = madagascar;
    }

但请坚持你的问题中的例子，其中Log和Madagascar是某种静态全局

public class ControllerCreationInterceptor : Ninject.Extensions.Interception.IInterceptor
{

    public void Intercept(Ninject.Extensions.Interception.IInvocation invocation)
    {
        try
        {
            invocation.Proceed();
        }
        catch(InvalidOperationException e)
        {
            if (e.InnerException is BubonicPlagueException)
            {
                Log.Error(e.InnerException, "CLOSE EVERYTHING!");
                Madagascar.ShutdownAllPorts();
                //DO SOMETHING WITH THE ORIGIONAL ERROR!
            }
            //DO SOMETHING WITH THE ORIGIONAL ERROR!
        }
    }
}

FINALLY在全局asax或App_Start（NinjectWebCommon）中注册拦截器

kernel.Bind<System.Web.Http.Dispatcher.IHttpControllerActivator>()
            .To<System.Web.Http.Dispatcher.DefaultHttpControllerActivator>().Intercept().With<ControllerCreationInterceptor>();

选项2 是实现您自己的Controller Activator实现IHttpControllerActivator接口，并在Create方法中处理创建Controller时的错误。您可以使用装饰器模式来包装DefaultHttpControllerActivator：

public class YourCustomControllerActivator : IHttpControllerActivator
{
    private readonly IHttpControllerActivator _default = new DefaultHttpControllerActivator();

    public YourCustomControllerActivator()
    {

    }

     public System.Web.Http.Controllers.IHttpController Create(System.Net.Http.HttpRequestMessage request, System.Web.Http.Controllers.HttpControllerDescriptor controllerDescriptor, Type controllerType)
    {
        try
        {
            return _default.Create(request, controllerDescriptor, controllerType);
        }
        catch (InvalidOperationException e)
        {
            if (e.InnerException is BubonicPlagueException)
            {
                Log.Error(e.InnerException, "CLOSE EVERYTHING!");
                Madagascar.ShutdownAllPorts();
                //DO SOMETHING WITH THE ORIGIONAL ERROR!
            }
            //DO SOMETHING WITH THE ORIGIONAL ERROR!
            return null;
        }

    }
}

一旦拥有自己的自定义激活器，默认激活器可以是全局asax中的switched out：

  GlobalConfiguration.Configuration.Services.Replace(typeof(IHttpControllerActivator), new YourCustomControllerActivator());

选项3 当然，如果你在构造函数中的初始化不需要访问实际的Controllers方法，属性等...即假设它可以从构造函数中删除...那么它将初始化移动到过滤器会更容易，例如

public class MadagascarFilter : AbstractActionFilter
{
    public override void OnActionExecuting(System.Web.Http.Controllers.HttpActionContext actionContext)
    {
    try{
          DoSomeInitialization(); // this can throw an exception
        }
        catch(BubonicPlagueException e){
    Log.Error(e, "CLOSE EVERYTHING!");
        Madagascar.ShutdownAllPorts();
            //DO SOMETHING WITH THE ERROR                           
        }

        base.OnActionExecuting(actionContext);
    }

public override void OnActionExecuted(System.Web.Http.Filters.HttpActionExecutedContext actionExecutedContext)
    {
        base.OnActionExecuted(actionExecutedContext);
    }

    public override bool AllowMultiple
    {
        get { return false; }
    }


}

我应该如何处理WebAPI中控制器构造函数中的异常？

1 个答案: