处理 ASP.NET Web api 服务中的错误

Question

我正在尝试处理 webapi 中服务部分的异常。 我试图实现的目标是：

当服务出现错误时，例如when didn't find the todo with certain id 控制器应该返回带有自定义状态码的自定义 json 响应。

因为在我的项目中控制器和服务是分开的，不知道如何实现它。

提前致谢。

在我的代码下面：

在Services/TodoRepository.cs

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
using test.Data;
using test.DTO;
using test.Interfaces;
using test.Models;

namespace test.Services
{
    public class TodoRepository : ITodoRepository
    {
        private readonly DataContext _context;

        public TodoRepository(DataContext context)
        {
            _context = context;
        }
        public async Task<IEnumerable<Todo>> GetTodosAsync()
        {
            return await _context.Todos.ToListAsync();
        }

        public async Task<Todo> GetTodoAsync(int id)
        {
            return await _context.Todos.FindAsync(id);
        }

        public async Task<Todo> AddTodoAsync(TodoInput input)
        {
            var todo = new Todo 
            {
                Title = input.Title,
                Description = input.Description,
                IsDone = input.IsDone
            };
            await _context.Todos.AddAsync(todo);
            return todo;
        }

        public async Task<Todo> SetTodoAsync(int id, TodoInput input)
        {
            var todo = await _context.Todos.FindAsync(id);
            if (todo == null)
                //
                // CONTROLLER SHOULD RETURN CUSTOM 
                // JSON RESPONSE WITH CUSTOM STATUS CODE
                // INSTEAD OF EXCEPTION WITH INTERNAL SERVER ERROR
                //
                throw new Exception("Could not find an item with this id");
            todo.Title = input.Title;
            todo.Description = input.Description;
            todo.IsDone = input.IsDone;
            todo.Updated = DateTime.Now;
            _context.Todos.Update(todo);
            return todo;
        }

        public async Task<Todo> DeleteTodoAsync(int id)
        {
            var todo = await _context.Todos.FindAsync(id);
            if (todo == null)
                //
                // CONTROLLER SHOULD RETURN CUSTOM 
                // JSON RESPONSE WITH CUSTOM STATUS CODE
                // INSTEAD OF EXCEPTION WITH INTERNAL SERVER ERROR
                //
                throw new Exception("Could not find an item with this id");
            _context.Todos.Remove(todo);
            return todo;
        }

        public async Task<bool> SaveAllAsync()
        {
            return await _context.SaveChangesAsync() > 0;
        }
    }
}

在Controllers/TodosController.cs

using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using test.Data;
using test.DTO;
using test.Interfaces;
using test.Models;

namespace test.Controllers
{
    [ApiController]
    [Route("[controller]")]
    public class TodosController : ControllerBase
    {
        private readonly DataContext _context;
        private ITodoRepository _repository;

        public TodosController(DataContext context, ITodoRepository repository)
        {
            _context = context;
            _repository = repository;
        }

        [HttpGet]
        public async Task<ActionResult<IEnumerable<Todo>>> GetTodos()
        {
            return Ok(await _repository.GetTodosAsync());
        }

        [HttpGet("{id}")]
        public async Task<ActionResult<Todo>> GetTodo([FromRoute] int id)
        {
            return Ok(await _repository.GetTodoAsync(id));
        }

        [HttpPost]
        public async Task<ActionResult<Todo>> AddTodo([FromBody] TodoInput input)
        {
            var todo = await _repository.AddTodoAsync(input);
            if (!await _repository.SaveAllAsync())
                return BadRequest("something gone wrong");
            return Ok(todo);
        }

        [HttpPut("{id}")]
        public async Task<ActionResult<Todo>> SetTodo([FromRoute] int id, [FromBody] TodoInput input)
        {
            var todo = await _repository.SetTodoAsync(id, input);
            if (!await _repository.SaveAllAsync())
                return BadRequest("something gone wrong");
            return Ok(todo);
        }
        [HttpDelete("{id}")]
        public async Task<ActionResult<Todo>> DeleteTodo([FromRoute] int id)
        {
            var todo = await _repository.DeleteTodoAsync(id);
            if (!await _repository.SaveAllAsync())
                return BadRequest("something gone wrong");
            return Ok(todo);
        }
    }
}

Answer 1

假设您将在某些方法中抛出一些特定的异常，而您只想将其捕获为 System.Exception，也许您可​​以使用这种方法：

您可以创建异常处理扩展方法（如果您也想使用 Logger，只需在方法中添加 ILogger 参数并从 Startup.Configure 传递它）：

public static class ExceptionHandler
    {
        /// <summary>
        /// 
        /// </summary>
        /// <param name="app"></param>
        public static void UseCustomExceptionHandler(this IApplicationBuilder app)
        {
            app.UseExceptionHandler(eApp =>
            {
                eApp.Run(async context =>
                {
                    context.Response.StatusCode = 500;
                    context.Response.ContentType = "application/json";

                    var errorCtx = context.Features.Get<IExceptionHandlerFeature>();
                    if (errorCtx != null)
                    {
                        var ex = errorCtx.Error;
                        var message = "Unspecified error ocurred.";

                        if (ex is ValidationException)
                        {
                            var validationException = ex as ValidationException;
                            context.Response.StatusCode = (int)HttpStatusCode.BadRequest;
                            message = string.Join(" | ", validationException.Errors.Select(v => string.Join(",", v.Value)));
                        }
                        else if (ex is SomeCustomException)
                        {
                            var someCustomException = ex as SomeCustomException;
                            ...
                        }

                        var jsonResponse = JsonConvert.SerializeObject(new ErrorResponse
                        {
                            TraceId = traceId,
                            Message = message
                        });
                        await context.Response.WriteAsync(jsonResponse, Encoding.UTF8);
                    }
                });
            });
        }
    }

然后你只需在 Startup Configure 中注册它：

public void Configure(IApplicationBuilder app)
        {
            ...

            app.UseCustomExceptionHandler();

            ...
        }

对于不同的异常可以设置不同的状态码：context.Response.StatusCode = 404;

Answer 2

因此，对于您的服务类，您将需要一个返回 BadResult 对象的 try/catch：

        try
        {
           //TODO Test Case check
           if(x != 1)
           {
              throw new Exception();

        }
        catch (Exception e)
        {
            return BadRequest("Could not find an item with this id");
        }

现在对于您的 ASP .Net 客户端上的控制器，当您检查您启动的任务的结果以调用您的 API 时：

               var acctResult = responseAcctTask.Result;

                if (acctResult.StatusCode == HttpStatusCode.BadRequest)
                {   
                    //log response status here..
                    ModelState.AddModelError(string.Empty, "Server error.");
                }

此时您可以以任何方式处理错误，我更喜欢将其添加到 modelState 以便我可以访问我的视图中的错误信息。