• ASP.NET Core Web API 幂等性

    API的幂等性（Idempotent），是指调用某个方法1次或N次对资源产生的影响结果都是相同的。
    GET请求默认是幂等的，因为它只是查询资源，而不会修改资源。
    而POST请求默认是不幂等的，多次调用POST方法可能会产生不同的结果，并会创建多个资源。
    想象一下，你在扫码支付时，输入金额后点击了2次“确定”按钮，肯定不希望扣2次款。
    幂等性保证了操作只会执行一次。

    1、思路
    使用ASP.NET Core过滤器来处理POST请求，检查请求头【Headers】中的幂等键（IdempotencyKey）。
    如果在缓存中未检查到IdempotencyKey，则真实执行操作并缓存响应数据，否则直接返回缓存的响应数据。
    这样，操作只能对资源产生一次影响。

    2、IdempotentAttributeFilter
    创建自定义Filter，使用OnActionExecuting方法在执行操作前检查缓存，如有缓存直接返回context.Result；使用OnResultExecuted方法在执行操作后缓存响应。

    1. using Microsoft.AspNetCore.Http;
    2. using Microsoft.AspNetCore.Mvc;
    3. using Microsoft.AspNetCore.Mvc.Filters;
    4. using Microsoft.Extensions.Caching.Distributed;
    5. using Newtonsoft.Json;
    6. using System;
    7. using System.Collections.Generic;
    8. using System.IO;
    9. using System.Linq;
    10. using System.Threading.Tasks;
    11.  
    12. namespace WebApi
    13. {
    14.     /// 
    15.     /// 
    16.     /// 
    17.     public class IdempotentAttributeFilter : IActionFilter, IResultFilter
    18.     {
    19.         private readonly IDistributedCache _distributedCache;
    20.         private bool _isIdempotencyCache = false;
    21.         const string IdempotencyKeyHeaderName = "IdempotencyKey";
    22.         private string _idempotencyKey;
    23.  
    24.         /// 
    25.         /// 
    26.         /// 
    27.         /// 
    28.         public IdempotentAttributeFilter(IDistributedCache distributedCache)
    29.         {
    30.             _distributedCache = distributedCache;
    31.         }
    32.  
    33.         /// 
    34.         /// 
    35.         /// 
    36.         /// 
    37.         public void OnActionExecuting(ActionExecutingContext context)
    38.         {
    39.             Microsoft.Extensions.Primitives.StringValues idempotencyKeys;
    40.             context.HttpContext.Request.Headers.TryGetValue(IdempotencyKeyHeaderName, out idempotencyKeys);
    41.             _idempotencyKey = idempotencyKeys.ToString();
    42.  
    43.             var cacheData = _distributedCache.GetString(GetDistributedCacheKey());
    44.             if (cacheData != null)
    45.             {
    46.                 context.Result = JsonConvert.DeserializeObject(cacheData);
    47.                 _isIdempotencyCache = true;
    48.                 return;
    49.             }
    50.         }
    51.  
    52.         /// 
    53.         /// 
    54.         /// 
    55.         /// 
    56.         public void OnResultExecuted(ResultExecutedContext context)
    57.         {
    58.             //已缓存
    59.             if (_isIdempotencyCache)
    60.             {
    61.                 return;
    62.             }
    63.  
    64.             var contextResult = context.Result;
    65.  
    66.             DistributedCacheEntryOptions cacheOptions = new DistributedCacheEntryOptions();
    67.  
    68.             //相对过期时间
    69.             //cacheOptions.SlidingExpiration = TimeSpan.FromSeconds(10);
    70.             //绝对过期时间
    71.             cacheOptions.AbsoluteExpirationRelativeToNow = new TimeSpan(24, 0, 0);
    72.  
    73.             //缓存:
    74.             _distributedCache.SetString(GetDistributedCacheKey(), JsonConvert.SerializeObject(contextResult), cacheOptions);
    75.         }
    76.  
    77.         /// 
    78.         /// 
    79.         /// 
    80.         /// 
    81.         public void OnActionExecuted(ActionExecutedContext context)
    82.         {
    83.         }
    84.  
    85.         /// 
    86.         /// 
    87.         /// 
    88.         /// 
    89.         public void OnResultExecuting(ResultExecutingContext context)
    90.         {
    91.         }
    92.  
    93.         private string GetDistributedCacheKey()
    94.         {
    95.             return "Idempotency:" + _idempotencyKey;
    96.         }
    97.     }
    98. }

    3、创建自定义Attribute
    声明了IdempotentAttribute的Class或者Method，在运行时会创建IdempotentAttributeFilter。

    1. using Microsoft.AspNetCore.Http;
    2. using Microsoft.AspNetCore.Mvc;
    3. using Microsoft.AspNetCore.Mvc.Filters;
    4. using Microsoft.Extensions.Caching.Distributed;
    5. using Newtonsoft.Json;
    6. using System;
    7. using System.Collections.Generic;
    8. using System.IO;
    9. using System.Linq;
    10. using System.Threading.Tasks;
    11.  
    12. namespace WebApi
    13. {
    14.     /// 
    15.     /// 
    16.     /// 
    17.     [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = false)]
    18.     public class IdempotentAttribute : Attribute, IFilterFactory
    19.     {
    20.         /// 
    21.         /// 
    22.         /// 
    23.         public bool IsReusable => false;
    24.  
    25.         /// 
    26.         /// 
    27.         /// 
    28.         /// 
    29.         /// 
    30.         public IFilterMetadata CreateInstance(IServiceProvider serviceProvider)
    31.         {
    32.             var distributedCache = (IDistributedCache)serviceProvider.GetService(typeof(IDistributedCache));
    33.  
    34.             var filter = new IdempotentAttributeFilter(distributedCache);
    35.             return filter;
    36.         }
    37.     }
    38. }

    4、新建ASP.NET Core Web API项目
    创建 WeatherForecastController 控制器，为Post方法加上【Idempotent】
    这里用一个静态变量模拟数据库，POST请求写入数据，GET请求读取数据

    1. using Microsoft.AspNetCore.Mvc;
    2. using Microsoft.Extensions.Logging;
    3. using System;
    4. using System.Collections.Generic;
    5. using System.Linq;
    6. using System.Net;
    7. using System.Threading.Tasks;
    8.  
    9. namespace WebApi.Controllers
    10. {
    11.     /// 
    12.     /// 
    13.     /// 
    14.     [Route("api/[controller]")]
    15.     [ApiController]
    16.     public class WeatherForecastController : ControllerBase
    17.     {
    18.         private static List _db = new List();
    19.  
    20.         private static readonly string[] Summaries = new[]
    21.         {
    22.             "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
    23.         };
    24.  
    25.         /// 
    26.         /// 
    27.         /// 
    28.         public WeatherForecastController()
    29.         {
    30.         }
    31.  
    32.         /// 
    33.         /// 
    34.         /// 
    35.         /// 
    36.         /// 
    37.         [Idempotent]
    38.         [HttpPost]
    39.         public WeatherForecast Post(int temperature)
    40.         {
    41.             var data = new WeatherForecast { TemperatureC = temperature };
    42.             _db.Add(data);
    43.  
    44.             return data;
    45.         }
    46.  
    47.         /// 
    48.         /// 
    49.         /// 
    50.         /// 
    51.         [HttpGet()]
    52.         public IEnumerable Get()
    53.         {
    54.             var rng = new Random();
    55.             return _db.Select(p => new WeatherForecast
    56.             {
    57.                 TemperatureC = p.TemperatureC,
    58.                 Summary = Summaries[rng.Next(Summaries.Length)]
    59.             })
    60.             .ToArray();
    61.         }
    62.     }
    63.  
    64.     public class WeatherForecast
    65.     {
    66.         public DateTime Date { get; set; }
    67.  
    68.         public int TemperatureC { get; set; }
    69.  
    70.         public int TemperatureF => 32 + (int)(TemperatureC / 0.5556);
    71.  
    72.         public string Summary { get; set; }
    73.     }
    74. }

    5、注册分布式缓存
    必须增加分布式缓存，用于保存幂等键的值和响应数据。
    管理 NuGet 程序包(N)...

    1. Microsoft.Extensions.Caching.SqlServer
    2. Microsoft.Extensions.Caching.Redis
    3. Microsoft.Extensions.Caching.StackExchangeRedis

    Startup.cs

    1. public void ConfigureServices(IServiceCollection services)
    2. {
    3.     //分布式 SQL Server 缓存
    4.     services.AddDistributedSqlServerCache(opt =>
    5.     {
    6.         opt.ConnectionString = Configuration.GetConnectionString("DefaultConnection");
    7.         opt.SchemaName = "dbo";
    8.         opt.TableName = "sys_distributed_cache";
    9.         opt.DefaultSlidingExpiration = TimeSpan.FromMinutes(10);
    10.         opt.ExpiredItemsDeletionInterval = TimeSpan.FromMinutes(5);
    11.     });
    12.  
    13.     //分布式 Redis 缓存
    14.     services.AddDistributedRedisCache(cfg =>
    15.     {
    16.         cfg.Configuration = Configuration.GetConnectionString("RedisConnection");
    17.     });
    18.  
    19.     //分布式 StackExchangeRedis 缓存 
    20.     services.AddStackExchangeRedisCache(options =>
    21.     {
    22.         options.Configuration = "localhost";
    23.         options.InstanceName = "SampleInstance";
    24.     });
    25.  
    26.     //分布式缓存
    27.     services.AddDistributedMemoryCache();
    28. }

    在数据库中新建一个名叫“CacheDB”的数据库，然后以管理员身份cmd运行下面指令，会创建一张名叫“CacheTable”表，相应的缓存信息都存在于这张表中。

    1. dotnet sql-cache create <connection string> <schema> <table>
    2.  
    3. dotnet sql-cache create "Server=localhost;User=sa;Password=000000;Database=CacheDB" dbo CacheTable

    成功后会提示【Table and index were created successfully】
    表结构

    1. CREATE TABLE [dbo].[CacheTable](
    2.     [Id] [nvarchar](449) NOT NULL,
    3.     [Value] [varbinary](max) NOT NULL,
    4.     [ExpiresAtTime] [datetimeoffset](7) NOT NULL,
    5.     [SlidingExpirationInSeconds] [bigint] NULL,
    6.     [AbsoluteExpiration] [datetimeoffset](7) NULL,
    7.  CONSTRAINT [pk_Id] PRIMARY KEY CLUSTERED 
    8. (
    9.     [Id] ASC
    10. )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
    11. ) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]
    12.  
    13. CREATE NONCLUSTERED INDEX [Index_ExpiresAtTime] ON [dbo].[CacheTable]
    14. (
    15.     [ExpiresAtTime] ASC
    16. )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]

    6、测试
    运行Web API，使用不同IdempotencyKey执行POST请求，然后获取数据

    code

    1. POST /api/WeatherForecast?temperature=1000 HTTP/1.1
    2. Host: localhost:8001
    3. IdempotencyKey: 1000

    *
    *

  • 相关阅读:
    Springboot求职招聘系统毕业设计源码250911
    flink 状态
    忧虑随日落一起消失&做事的三重门
    复现一个循环以及俩个循环问题
    前端面试0906
    3-2 中阶API示范
    【PCB专题】如何在嘉立创8月1日起的新规则下免费打样
    项目管理中最常见的问题有哪些?
    Cholesterol艾美捷胆固醇基参方案
    部署k8s集群
  • 原文地址：https://blog.csdn.net/KingCruel/article/details/126014937