在ASP.NET Core里，我们可以使用中间件(Middleware)实现全局的异常处理。 如内置的异常处理中间件 UseExceptionHandler
app.UseExceptionHandler(appError =>
{
appError.Run(async context =>
{
context.Response.StatusCode = (int)HttpStatusCode.InternalServerError;
context.Response.ContentType = "application/json";
var contextFeature = context.Features.Get<IExceptionHandlerFeature>();
if (contextFeature != null)
{
logger.LogError($"Something went wrong: {contextFeature.Error}");
await context.Response.WriteAsync(new ErrorDetails()
{
StatusCode = context.Response.StatusCode,
Message = "Internal Server Error."
}.ToString());
}
});
});
或者如下干脆完全自定义一个中间件
public class ExceptionMiddleware
{
private readonly RequestDelegate _next;
private readonly ILoggerManager _logger;
public ExceptionMiddleware(RequestDelegate next, ILoggerManager logger)
{
_logger = logger;
_next = next;
}
public async Task InvokeAsync(HttpContext httpContext)
{
try
{
await _next(httpContext);
}
catch (Exception ex)
{
_logger.LogError($"Something went wrong: {ex}");
await HandleExceptionAsync(httpContext, ex);
}
}
private async Task HandleExceptionAsync(HttpContext context, Exception exception)
{
context.Response.ContentType = "application/json";
context.Response.StatusCode = (int)HttpStatusCode.InternalServerError;
await context.Response.WriteAsync(new ErrorDetails()
{
StatusCode = context.Response.StatusCode,
Message = "Internal Server Error from the custom middleware."
}.ToString());
}
}
当然还可以使用过滤器(Filter)来实现，即IExceptionFilter， 这些都能很方便实现自定义的全局异常处理。
在.NET 8.0里，微软新引入的IExceptionHandler也可以实现同样的功能，看官方的异常处理文档，IExceptionHandler似乎已经是最推荐的异常处理方法。
在微软新开的项目里，IExceptionHandler正被广泛使用，比如Semantic Kernel
下面是官方文档给的一个简单实现
using Microsoft.AspNetCore.Diagnostics;
namespace ErrorHandlingSample
{
public class CustomExceptionHandler : IExceptionHandler
{
private readonly ILogger<CustomExceptionHandler> logger;
public CustomExceptionHandler(ILogger<CustomExceptionHandler> logger)
{
this.logger = logger;
}
public ValueTask<bool> TryHandleAsync(
HttpContext httpContext,
Exception exception,
CancellationToken cancellationToken)
{
var exceptionMessage = exception.Message;
logger.LogError(
"Error Message: {exceptionMessage}, Time of occurrence {time}",
exceptionMessage, DateTime.UtcNow);
// Return false to continue with the default behavior
// - or - return true to signal that this exception is handled
return ValueTask.FromResult(false);
}
}
}
使用也很简单
builder.Services.AddExceptionHandler<CustomExceptionHandler>();
然而，如果你按照文档实现完之后，你所期待的自定义异常处理并不会生效，你必须添加一个空的lambda给UseExceptionHandler，AddExceptionHandler才会生效：)
app.UseExceptionHandler(o => { });
为什么会这样？看这个https://github.com/dotnet/aspnetcore/issues/51888, 去年下半年就有人发现了，微软尝试修复https://github.com/dotnet/aspnetcore/pull/51898， 但是改动有breaking change给拒绝了，加上有上面提到的workaround，就一直搁置了。
虽然又不是不能用，但是看着难受，开头就介绍了，UseExceptionHandler是启用内置的异常处理中间件，AddExceptionHandler是用来注册.NET 8.0新引入的IExceptionHandler，这个神奇workaround太一言难尽，欢迎踊跃提交PR去fix，先到先得☺