示例介绍
示例1：借助Redis实现购物车功能
示例2：Redis实现网页缓存和数据缓存
借助Redis实现购物车功能
每个用户的购物车都是一个散列，散列存储了商品ID与商品订购数量之间的映射。订购商品时，对购物车进行更新：如果用户订购某件商品的数量大于0，那么将这件商品的ID以及用户订购该商品的数量添加到散列里面，如果用户购买的商品已经存在散列里面，那么新的订购数量会覆盖已有的订购数量；相反，如果用户订购某件商品数量不大于0，那么程序将从散列里面移除该条目。
由于整个示例分Controller和WebApi两部分，在不考虑封装Redis操作的情况下提取Redis连接字符串到appSetting.json中
"ConnectionStrings": {
"Redis": "localhost,abortConnect=false"
},
保存用户购物查数据示例代码：
[HttpGet("UpdateCart")]
public string UpdateCart(string token,string item,int count)
{
var key = $"cart:{token}";
using (var redis = ConnectionMultiplexer.Connect(redisConnectionStr))
{
var db = redis.GetDatabase();
//更新购物车数据
if (count <= 0)
{
db.HashDeleteAsync(key, item);
}
else
{
db.HashSetAsync(key, item,count);
}
}
return "更新购物车成功";
}
Redis实现网页缓存和数据缓存
针对不会频繁更新得动态网页或Ajax返回的数据可以缓存在Redis中，减少与数据库的交互提升系统效应效率。
该示例只是为了演示借助Reids实现页面缓存和数据缓存效果，实际使用中可通过ResponseCache特性实现缓存。
详细介绍：https://docs.microsoft.com/en-us/aspnet/core/performance/caching/response?view=aspnetcore-5.0
网页数据缓存
新建示例项目时为WebApi项目，修改Startup类添加Web Mvc支持。
ConfigureServices方法中修改services.AddControllers()为services.AddControllersWithViews()。
Configure方法中app.UseEndpoints修改为如下代码
app.UseEndpoints(endpoints =>
{
endpoints.MapControllerRoute(
name: "default",
pattern: "{controller=Home}/{action=Index}/{id?}");
});
定义中间件类RedisCacheMiddleware，用来缓存网页页面
public class RedisCacheMiddleware
{ private readonly RequestDelegate _next; public IConfiguration Configuration { get; } public RedisCacheMiddleware(RequestDelegate next, IConfiguration configuration)
{
_next = next;
Configuration = configuration;
} public async Task InvokeAsync(HttpContext context)
{ var path = context.Request.Path.Value.ToLower(); if (path == "/home" || path == "/home/index")
{ var responseContent = ""; //Copy a pointer to the original response body stream
var originalBodyStream = context.Response.Body; using (var redis = ConnectionMultiplexer.Connect(Configuration.GetConnectionString("Redis")))
{
var db = redis.GetDatabase();
if (db.KeyExists(path))
{
responseContent = db.StringGet(path);
await RespondWithIndexHtml(context.Response, responseContent);
return;
}
else
{
using (var responseBody = new MemoryStream())
{
//...and use that for the temporary response body
context.Response.Body = responseBody; //Continue down the Middleware pipeline, eventually returning to this class
await _next(context); //Format the response from the server
responseContent = await FormatResponse(context.Response); //Copy the contents of the new memory stream (which contains the response) to the original stream, which is then returned to the client.
await responseBody.CopyToAsync(originalBodyStream);
} db.StringSet(path, responseContent, expiry: TimeSpan.FromSeconds(30));
}
} } // Call the next delegate/middleware in the pipeline
await _next(context);
} private async Task RespondWithIndexHtml(HttpResponse response,string html)
{
response.StatusCode = 200;
response.ContentType = "text/html"; await response.WriteAsync(html, Encoding.UTF8);
} private async Task<string> FormatResponse(HttpResponse response)
{
//We need to read the response stream from the beginning...
response.Body.Seek(0, SeekOrigin.Begin); //...and copy it into a string
string text = await new StreamReader(response.Body).ReadToEndAsync(); //We need to reset the reader for the response so that the client can read it.
response.Body.Seek(0, SeekOrigin.Begin); //Return the string for the response
return text;
} }
添加中间件调用
app.UseMiddleware<RedisCacheMiddleware>();
运行效果如图:
网页上的时间会每30秒更新一次。
.Net Core提供的响应缓存中间件：https://docs.microsoft.com/zh-cn/aspnet/core/performance/caching/middleware?view=aspnetcore-5.0
Ajax数据缓存
本例只是简单的数据存储，实际使用中可编写单独的服务，让这个服务将指定的数据缓存到Redis里面，并不定期地对这些缓存进行更新。
示例代码
[HttpGet("GetDateTime")]
public string GetDateTime()
{
var dateTime = "";
var key = "data:datetime";
using (var redis = ConnectionMultiplexer.Connect(redisConnectionStr))
{
var db = redis.GetDatabase();
if (db.KeyExists(key))
{
dateTime = db.StringGet(key);
}
else
{
dateTime = DateTimeOffset.Now.ToString("yyyy-MM-dd HH:mm:ss");
db.StringSet(key, dateTime,expiry:TimeSpan.FromSeconds(5));
}
}
return dateTime;
}