DOTNET CORE WEB API 统一模型验证拦截器

参考:

• https://code-maze.com/action-filters-aspnetcore/
• https://github.com/aspnet/AspNetCore.Docs/issues/12157
• https://docs.microsoft.com/en-us/aspnet/core/web-api/?view=aspnetcore-3.0#automatic-http-400-responses

1. 关闭默认模型验证过滤器
   [ApiController] 默认自带有400模型验证，且优先级比较高，如果需要自定义模型验证，则需要先关闭默认的模型验证
   在StartUp.cs 中的MVC服务配置修改

   #region MVC
   services.AddMvc(o =>
   {
   }).SetCompatibilityVersion(CompatibilityVersion.Version_2_2)
   .ConfigureApiBehaviorOptions(o =>
   {
       o.SuppressModelStateInvalidFilter = true;
   });
    #endregion
   

2. 首先定义统一输出的格式为

   {
       code:
       errors:[
           filed:
           message:
       ]
   }
   

3. 添加自定义模型验证DTO

    public class ErrorResultDTO
       {
           /// <summary>
           /// 参数领域
           /// </summary>
           public string Field { get; set; }
   
           /// <summary>
           /// 错误信息
           /// </summary>
           public string Message { get; set; }   
       }
   

4.  添加过滤器
    过滤器继承自:ActionFilterAttribute, IActionFilter
    ``` c#
    public class ModelActionFiter :ActionFilterAttribute, IActionFilter
        {
            public ModelActionFiter()
            {
            }
            public override void OnActionExecuted(ActionExecutedContext context)
            {
                
            }

           public override void OnActionExecuting(ActionExecutingContext context)
            {
                if (!context.ModelState.IsValid)
                {     
                    List<ErrorResultDTO> errorResults = new List<ErrorResultDTO>();
                    foreach (var item in context.ModelState)
                    {
                        var result = new ErrorResultDTO
                        {
                            Field = item.Key,
                            Msg = "",
                        };
                        foreach (var error in item.Value.Errors)
                        {
                            if (!string.IsNullOrEmpty(result.Msg))
                            {
                                result.Msg += '|';
                            }
                            result.Msg += error.ErrorMessage;
                        }
                        errorResults.Add(result);
                    }
                    context.Result = new BadRequestObjectResult(new
                    {
                        Code = StatusCodes.Status400BadRequest,
                       Errors = errorResults
                    });  
                }
            }
        }
    ```
5. 将写的过滤器注册到全局

    ``` c#  
      services.AddMvc(o =>
            {
                o.Filters.Add(new ModelActionFiter());
       })

6. 结果测试
   

7. 扩展

   • 利用拦截器来测试action 的运行时间，记录日志，并设置时间限制，超过某个时间段自动发送邮件通知维护人员