aspnetcore使用websocket实时更新商品信息

先演示一下效果，再展示代码逻辑。

中间几次调用过程省略。。。

暂时只用到了下面四个项目

1.产品展示页面中第一次通过接口去获取数据库的列表数据

/// <summary>
/// 获取指定的商品目录
/// </summary>
/// <param name="pageSize"></param>
/// <param name="pageIndex"></param>
/// <param name="ids"></param>
/// <returns></returns>
[HttpGet]
[Route("items")]
[ProducesResponseType(typeof(PaginatedViewModel<Catalog>), StatusCodes.Status200OK)]
[ProducesResponseType(typeof(IEnumerable<ProductDto>), StatusCodes.Status200OK)]
[ProducesResponseType(StatusCodes.Status400BadRequest)]
public async Task<IActionResult> Catalogs([FromQuery] int pageSize = 10, [FromQuery] int pageIndex = 0, string ids = null)
{
    if (!string.IsNullOrEmpty(ids))
    {
        var items = awAIt GetItemByIds(ids);
        if (!items.Any())
        {
            return BadRequest("ids value invalid. Must be comma-separated list of numbers");
        }

        return Ok(items);
    }

    var totalItems = await _catalogContext.Catalogs
        .LongCountAsync();

    var itemsOnPage = await _catalogContext.Catalogs
        .OrderBy(c => c.Name)
        .Skip(pageSize * pageIndex)
        .Take(pageSize)
        .ToListAsync();
    var result = itemsOnPage.Select(x => new ProductDto(x.Id.ToString(), x.Name, x.Price.ToString(), x.Stock.ToString(), x.ImgPath));
    var model = new PaginatedViewModel<ProductDto>(pageIndex, pageSize, totalItems, result);
    return Ok(model);

}

2.在前端页面会把当前页面的产品列表id都发送到websocket中去

 function updateAndSendProductIds(ids) {
     productIds = ids;

     // Check if the WebSocket is open
     if (socket.readyState === WebSocket.OPEN) {
         // Send the list of product IDs through the WebSocket connection
         socket.send(JSON.stringify(productIds));
     }
 }

 function fetchData() {
    
     const apiUrl = baseUrl + `/Catalog/items?pageSize=${pageSize}&pageIndex=${currentPage}`;

     axios.get(apiUrl)
         .then(response => {
             const data = response.data.data;
             displayProducts(baseUrl, data);

             const newProductIds = data.map(product => product.Id);
             // Check if the WebSocket is open
             updateAndSendProductIds(newProductIds);
             // 从响应中获取总页数
             const totalPages = Math.ceil(response.data.count / pageSize);
             displayPagination(totalPages);

             // 更新当前页数的显示
             const currentPageElement = document.getElementById('currentPage');
             currentPageElement.textContent = `当前页数: ${currentPage + 1} / 总页数: ${totalPages}`;
         })
         .catch(error => {
             console.error('获取数据失败:', error);
         });
 }

3.websocket拿到了id数据可以精确的把当前页面的产品都查出来再推送给product.html页面，通过下面的ReceiveAsync方法获取html发送的数据，再通过timer定时器每秒钟Send方法实时的往页面发送获取到的数据，当然这个是不断的去从redis中去查的。

using System.Net.WebSockets;
using System.Threading.Tasks;
using System;
using WsServer.Handler;
using WsServer.Manager;
using StackExchange.Redis;
using Microsoft.Extensions.Configuration;
using System.Collections.Generic;
using Catalogs.Domain.Catalogs;
using Catalogs.Domain.Dtos;
using System.Net.Sockets;

namespace WebScoket.Server.Services
{
    /// <summary>
    /// 实时推送产品主要是最新的库存，其他信息也会更新
    /// </summary>
    public class ProductListHandler : WebSocketHandler
    {
        private System.Threading.Timer _timer;
        private readonly IDatabase _redisDb;
        //展示列表推送
        private string productIdsStr;
        public ProductListHandler(WebSocketConnectionManager webSocketConnectionManager,IConfiguration configuration) : base(webSocketConnectionManager)
        {
            ConnectionMultiplexer redis = ConnectionMultiplexer.Connect(configuration["DistributedRedis:ConnectionString"] ?? throw new Exception("$未能获取distributedredis连接字符串"));
            _redisDb = redis.GetDatabase();
            _timer = new System.Threading.Timer(Send, null, TimeSpan.Zero, TimeSpan.FromSeconds(1));
        }
        private void Send(object state)
        {
            // 获取当前时间并发送给所有连接的客户端
            if (productIdsStr != null)
            {
                string[] productIds = System.Text.Json.JsonSerializer.Deserialize<string[]>(productIdsStr);
                string hashKeyToRetrieve = "products";
                List<ProductDto> products = new List<ProductDto>();

                foreach (var productId in productIds)
                {
                    if(productId == "null") {
                        continue;
                    }
                    string retrievedProductValue = _redisDb.HashGet(hashKeyToRetrieve, productId);
                    if (!string.IsNullOrEmpty(retrievedProductValue))
                    {
                        //反序列化和构造函数冲突，改造了一下Catalog
                        Catalog catalog = System.Text.Json.JsonSerializer.Deserialize<Catalog>(retrievedProductValue);
                        products.Add(new ProductDto(catalog.Id.ToString(), catalog.Name, catalog.Price.ToString(), catalog.Stock.ToString(), catalog.ImgPath));
                    }
                }
                if (products.Count > 0)
                {
                     SendMessageToAllAsync(System.Text.Json.JsonSerializer.Serialize(products)).Wait();
                }
                else
                {
                    SendMessageToAllAsync("NoProduct").Wait();
                }
            }
        }
        public override async Task ReceiveAsync(WebSocket socket, WebSocketReceiveResult result, byte[] buffer)
        {
            //每次页面有刷新就会拿到展示的id列表
            productIdsStr = System.Text.Encoding.UTF8.GetString(buffer, 0, result.Count);
        }
    }
}

4.html页面就可以拿到最新数据再去绑定到页面

socket.addEventListener('message', (event) => {
    if (event.data == "NoProduct") {
        clearProductList();
    }
    // Handle the received product data and update the product list
    const productData = JSON.parse(event.data);
    // Update the product list with the received data (call your displayProducts function)
    displayProducts(baseUrl, productData);
});

整个流程就这么简单，但是这里需要保持数据库和redis的数据实时同步，否则页面展示的就不是最新的数据就没意义了。

再回到Catalog.Service服务中。

 private async Task DeleteCache()
 {
     //await _redisDb.HashDeleteAsync("products",id); //没必要了
     await _channel.Writer.WriteAsync("delete_catalog_fromredis");
 }

再做更新、新增、删除等动作的时候就调用一下DeleteCache方法，往后台服务发送一个channel,当后台收到后就做redis删除并且从初始化sqlserver到redis列表同步的操作

using System.Reflection;
using System.Threading.Channels;
using Catalogs.Infrastructure.Database;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using StackExchange.Redis;

namespace Catalogs.WebApi.BackgroudServices
{
    /// <summary>
    /// 记得任何删除了或者购买了产品后需要删除改产品的键
    /// </summary>
    public class InitProductListToRedisService : BackgroundService
    {
        private readonly IServiceScopeFactory _serviceScopeFactory;
        private readonly IDatabase _redisDb;
        private readonly Channel<string> _channel;
        private readonly ILogger _logger;
        public InitProductListToRedisService(IServiceScopeFactory serviceScopeFactory, IConfiguration configuration, Channel<string> channel, ILogger<InitProductListToRedisService> logger)
        {
            _serviceScopeFactory = serviceScopeFactory;
            ConnectionMultiplexer redis = ConnectionMultiplexer.Connect(configuration["DistributedRedis:ConnectionString"] ?? throw new Exception("$未能获取distributedredis连接字符串"));
            _redisDb = redis.GetDatabase();
            _channel = channel;
            _logger = logger;
        }
        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            await Init();

            while (!_channel.Reader.Completion.IsCompleted)
            {
                var msg = await _channel.Reader.ReadAsync();
                if(msg == "delete_catalog_fromredis")
                {
                    await Init();
                }
            }
        }

        private async Task Init()
        {
            using var scope = _serviceScopeFactory.CreateScope();
            try
            {
                CatalogContext _context = scope.ServiceProvider.GetRequiredService<CatalogContext>();
                string hashKey = "products";
                var products = await _context.Catalogs.ToListAsync();
               
                   await _redisDb.KeyDeleteAsync(hashKey);
                
                    foreach (var product in products)
                    {
                        
                        string productField = product.Id.ToString();
                        string productValue = System.Text.Json.JsonSerializer.Serialize(product);

                        _redisDb.HashSet(hashKey, new HashEntry[] { new HashEntry(productField, productValue) });
                    }

                    _logger.LogInformation($"ProductList is over stored in Redis Hash.");           
            }
            catch(Exception ex)
            {
                _logger.LogError($"ProductLis stored in Redis Hash error.");
            }
        }
    }
}

这里还有优化的空间可以只针对怕products的hashset的某个id去更新、删除、新增一条数据。

示例代码：

liuzhixin405/efcore-template (github.com)