.Net Core webapi RestFul 统一接口数据返回格式

在RestFul风格盛行的年代，大部分接口都需要一套统一的数据返回格式，那么我们怎么才能保证使用统一的json数据格式返回呢，下面给大家简单介绍一下：

假如我们需要接口统一返回一下数据格式：

{
  "statusCode": 200,
  "successful": true,
  "message": null,
  "data": object
}

json对象中data是返回的实际结果对象，可以是一个对象、一个list、一个字符串、一个数字......

但是整体的json格式要以上面的为准

一般这种情况我们有两种实现方式：

1、自定义一个统一返回类

2、使用过滤器(Filter)实现

下面先介绍第一种，自定义一个接口返回类：

创建对应的接口类和实现类

ApiResponse.cs//实现类
IApiResponse.cs://几个相关的接口

IApiResponse.cs

    public interface IApiResponse
    {
        public int StatusCode { get; set; }
        public bool Successful { get; set; }
        public string? Message { get; set; }
    }

    public interface IApiResponse<T> : IApiResponse
    {
        public T? Data { get; set; }
    }

    public interface IApiErrorResponse
    {
        public Dictionary<string, object> ErrorData { get; set; }
    }

保证了所有相关对象都来自 IApiResponse 接口

ApiResponse.cs

    public class ApiResponse<T> : IApiResponse<T>
    {
        public ApiResponse()
        {
        }

        public ApiResponse(T? data)
        {
            Data = data;
        }

        public int StatusCode { get; set; } = 200;
        public bool Successful { get; set; } = true;
        public string? Message { get; set; }

        public T? Data { get; set; }

        /// <summary>
        /// 实现将 <see cref="ApiResponse"/> 隐式转换为 <see cref="ApiResponse{T}"/>
        /// </summary>
        /// <param name="apiResponse"><see cref="ApiResponse"/></param>
        public static implicit operator ApiResponse<T>(ApiResponse apiResponse)
        {
            return new ApiResponse<T>
            {
                StatusCode = apiResponse.StatusCode,
                Successful = apiResponse.Successful,
                Message = apiResponse.Message
            };
        }
    }


    public class ApiResponse : IApiResponse, IApiErrorResponse
    {
        public int StatusCode { get; set; } = 200;
        public bool Successful { get; set; } = true;
        public string? Message { get; set; }
        public object? Data { get; set; }

        /// <summary>
        /// 可序列化的错误
        /// <para>用于保存模型验证失败的错误信息</para>
        /// </summary>
        public Dictionary<string, object>? ErrorData { get; set; }

        public ApiResponse()
        {
        }

        public ApiResponse(object data)
        {
            Data = data;
        }

        public static ApiResponse NoContent(string message = "NoContent")
        {
            return new ApiResponse
            {
                StatusCode = StatusCodes.Status204NoContent,
                Successful = true,
                Message = message
            };
        }

        public static ApiResponse Ok(string message = "Ok")
        {
            return new ApiResponse
            {
                StatusCode = StatusCodes.Status200OK,
                Successful = true,
                Message = message
            };
        }

        public static ApiResponse Ok(object data, string message = "Ok")
        {
            return new ApiResponse
            {
                StatusCode = StatusCodes.Status200OK,
                Successful = true,
                Message = message,
                Data = data
            };
        }

        public static ApiResponse Unauthorized(string message = "Unauthorized")
        {
            return new ApiResponse
            {
                StatusCode = StatusCodes.Status401Unauthorized,
                Successful = false,
                Message = message
            };
        }

        public static ApiResponse NotFound(string message = "NotFound")
        {
            return new ApiResponse
            {
                StatusCode = StatusCodes.Status404NotFound,
                Successful = false,
                Message = message
            };
        }

        public static ApiResponse BadRequest(string message = "BadRequest")
        {
            return new ApiResponse
            {
                StatusCode = StatusCodes.Status400BadRequest,
                Successful = false,
                Message = message
            };
        }

        public static ApiResponse BadRequest(ModelStateDictionary modelState, string message = "ModelState is not valid.")
        {
            return new ApiResponse
            {
                StatusCode = StatusCodes.Status400BadRequest,
                Successful = false,
                Message = message,
                ErrorData = new SerializableError(modelState)
            };
        }

        public static ApiResponse Error(string message = "Error", Exception? exception = null)
        {
            object? data = null;
            if (exception != null)
            {
                data = new
                {
                    exception.Message,
                    exception.Data
                };
            }

            return new ApiResponse
            {
                StatusCode = StatusCodes.Status500InternalServerError,
                Successful = false,
                Message = message,
                Data = data
            };
        }
    }

分别实现类带有泛型的 ApiResponse<T> 类和 ApiResponse 类

注意在泛型类中，使用运算符重载，实现了 ApiResponse 到 ApiResponse<T> 的隐式转换。

在接口实现处返回一个 ApiResponse<T> 对象：

        [HttpGet]
        public ApiResponse<UserEntity> Get(string name)
        {
            var list = new List<UserEntity>() 
            {
                new UserEntity() { Name = "张三" },
                new UserEntity(){Name = "李四"}
            };
            var user = list.Find(p => p.Name == name);
            return user == null ? ApiResponse.NotFound() : new ApiResponse<UserEntity>(user);
        }

注意看最后一句