526互联

MemoryCache

发布时间 2023-06-08 00:57:25作者: 广州大雄

在asp.core中可以添加缓存服务

public void ConfigureServices(IServiceCollection services)
{
	//添加内存缓存
	services.AddMemoryCache();
}

从源码可以发现services.AddMemoryCache();使用单例模式注入我们程序中。

/// <summary>
/// Adds a non distributed in memory implementation of <see cref="IMemoryCache"/> to the
/// <see cref="IServiceCollection" />.
/// </summary>
/// <param name="services">The <see cref="IServiceCollection" /> to add services to.</param>
/// <returns>The <see cref="IServiceCollection"/> so that additional calls can be chained.</returns>
public static IServiceCollection AddMemoryCache(this IServiceCollection services)
{
	if (services == null)
	{
		throw new ArgumentNullException(nameof(services));
	}
	services.AddOptions();
	services.TryAdd(ServiceDescriptor.Singleton<IMemoryCache, MemoryCache>());
	return services;
}

与我们自己写的MemoryCacheHelper类，有异曲同工之秒

public class MemoryCacheHelper
{
	public static IMemoryCache _memoryCache = new MemoryCache(new MemoryCacheOptions());

	/// <summary>
	/// 获取缓存数据
	/// </summary>
	/// <typeparam name="T"></typeparam>
	/// <param name="key"></param>
	/// <returns></returns>
	public static T Get<T>(string key)
	{
		return _memoryCache.Get<T>(key);
	}

	/// <summary>
	/// 获取缓存数据
	/// </summary>
	/// <param name="key"></param>
	/// <returns></returns>
	public static string GetString(string key)
	{
		return _memoryCache.Get(key)?.ToString();
	}

	/// <summary>
	/// 设置缓存数据
	/// </summary>
	/// <param name="key"></param>
	/// <param name="value"></param>
	/// <param name="relative">绝对过期时间，例如relative是10分钟，那么缓存在10分钟后过期</param>
	/// <param name="offset">滑动过期时间，例如offset是10分钟，最后一次访问的10分钟后过期</param>
	public static void Set(string key, object value, TimeSpan? relative = null, TimeSpan? offset = null)
	{
		if (relative != null)
		{
			//缓存绝对过期时间，例如relative是10分钟，那么缓存在10分钟后过期
			cacheInsertAddMinutes(key, value, relative.Value);
		}
		else if (offset != null)
		{
			//缓存相对过期，例如offset是10分钟，最后一次访问的10分钟后过期
			cacheInsertFromMinutes(key, value, offset.Value);
		}
		else
		{
			//不设置过期时间
			cacheInsert(key, value);
		}
	}

	/// <summary>
	/// 清除缓存
	/// </summary>
	///<param name="key"></param>
	public static void Remove(string key)
	{
		_memoryCache.Remove(key);
	}

	/// <summary>
	/// 缓存绝对过期时间
	/// </summary>
	///<param name="key"></param>
	///<param name="value"></param>
	///<param name="expired">绝对过期时间</param>
	private static void cacheInsertAddMinutes(string key, object value, TimeSpan expired)
	{
		_memoryCache.Set(key, value, new MemoryCacheEntryOptions().SetAbsoluteExpiration(expired));
	}


	/// <summary>
	/// 缓存相对过期，最后一次访问的minute分钟后过期
	/// </summary>
	///<param name="key"></param>
	///<param name="value"></param>
	///<param name="expired">滑动过期时间</param>
	private static void cacheInsertFromMinutes(string key, object value, TimeSpan expired)
	{
		_memoryCache.Set(key, value, new MemoryCacheEntryOptions().SetSlidingExpiration(expired));
	}


	/// <summary>
	///以key键值，把value赋给Cache[key].如果不主动清空，会一直保存在内存中.
	/// </summary>
	///<param name="key">Cache键值</param>
	///<param name="value">给Cache[key]赋的值</param>
	private static void cacheInsert(string key, object value)
	{
		_memoryCache.Set(key, value);
	}
}

asp.core使用（构造注入）

private readonly ILogger<WeatherForecastController> _logger;
private readonly IMemoryCache _cache;

public WeatherForecastController(ILogger<WeatherForecastController> logger, 
	IMemoryCache cache)
{
	_logger = logger;
	_cache = cache;
}

[HttpGet]
public async Task<IActionResult> Test(string id)
{
	_cache.Set("key", "value");
	var cc = _cache.Get("key");
	//绝对过期时间
	_cache.Set("key", "value", new MemoryCacheEntryOptions().SetAbsoluteExpiration(TimeSpan.FromSeconds(1)));
	//滑动过期，最后一次访问的minute分钟后过期
	_cache.Set("key", "value", new MemoryCacheEntryOptions().SetSlidingExpiration(TimeSpan.FromSeconds(1)));
	return Ok();
}