如何在 ASP.NET MVC 中缓存对象？-Java 学习之路

我想在 ASP.NET MVC 中缓存对象。我有BaseController，我希望所有控制器继承。在 BaseController 中有一个User属性，它只是从数据库中获取用户数据，这样我就可以在控制器中使用它，或者将它传递给视图。

我想缓存这些信息。我在每个页面上都使用此信息，因此无需每个页面请求转到数据库。

我喜欢这样的东西：

if(_user is null)
  GrabFromDatabase
  StuffIntoCache
return CachedObject as User

如何在 ASP.NET MVC 中实现简单缓存？

8 回答

69
您仍然可以使用缓存(在所有响应中共享)和会话(每个用户唯一)进行存储。

我喜欢以下“尝试从 cache/create 和存储”模式(c#-like 伪代码)：
```
public static class CacheExtensions
{
  public static T GetOrStore<T>(this Cache cache, string key, Func<T> generator)
  {
    var result = cache[key];
    if(result == null)
    {
      result = generator();
      cache[key] = result;
    }
    return (T)result;
  }
}
```
你会这样使用它：
```
var user = HttpRuntime
              .Cache
              .GetOrStore<User>(
                 $"User{_userId}", 
                 () => Repository.GetUser(_userId));
```
您可以将此模式调整为 Session，ViewState(ugh)或任何其他缓存机制。你也可以扩展 ControllerContext.HttpContext(我认为它是 System.Web.Extensions 中的包装器之一)，或者创建一个新类来做一些模拟缓存的空间。
回复于 2024-05-02T12:13:04+08:00

我接受了 Will 的回答并对其进行了修改以使CacheExtensions类保持静态并建议稍微改动以便处理Func<T>为null的可能性：

public static class CacheExtensions
{

    private static object sync = new object();
    public const int DefaultCacheExpiration = 20;

    /// <summary>
    /// Allows Caching of typed data
    /// </summary>
    /// <example><![CDATA[
    /// var user = HttpRuntime
    ///   .Cache
    ///   .GetOrStore<User>(
    ///      string.Format("User{0}", _userId), 
    ///      () => Repository.GetUser(_userId));
    ///
    /// ]]></example>
    /// <typeparam name="T"></typeparam>
    /// <param name="cache">calling object</param>
    /// <param name="key">Cache key</param>
    /// <param name="generator">Func that returns the object to store in cache</param>
    /// <returns></returns>
    /// <remarks>Uses a default cache expiration period as defined in <see cref="CacheExtensions.DefaultCacheExpiration"/></remarks>
    public static T GetOrStore<T>( this Cache cache, string key, Func<T> generator ) {
        return cache.GetOrStore( key, (cache[key] == null && generator != null) ? generator() : default( T ), DefaultCacheExpiration );
    }

    /// <summary>
    /// Allows Caching of typed data
    /// </summary>
    /// <example><![CDATA[
    /// var user = HttpRuntime
    ///   .Cache
    ///   .GetOrStore<User>(
    ///      string.Format("User{0}", _userId), 
    ///      () => Repository.GetUser(_userId));
    ///
    /// ]]></example>
    /// <typeparam name="T"></typeparam>
    /// <param name="cache">calling object</param>
    /// <param name="key">Cache key</param>
    /// <param name="generator">Func that returns the object to store in cache</param>
    /// <param name="expireInMinutes">Time to expire cache in minutes</param>
    /// <returns></returns>
    public static T GetOrStore<T>( this Cache cache, string key, Func<T> generator, double expireInMinutes ) {
        return cache.GetOrStore( key,  (cache[key] == null && generator != null) ? generator() : default( T ), expireInMinutes );
    }

    /// <summary>
    /// Allows Caching of typed data
    /// </summary>
    /// <example><![CDATA[
    /// var user = HttpRuntime
    ///   .Cache
    ///   .GetOrStore<User>(
    ///      string.Format("User{0}", _userId),_userId));
    ///
    /// ]]></example>
    /// <typeparam name="T"></typeparam>
    /// <param name="cache">calling object</param>
    /// <param name="key">Cache key</param>
    /// <param name="obj">Object to store in cache</param>
    /// <returns></returns>
    /// <remarks>Uses a default cache expiration period as defined in <see cref="CacheExtensions.DefaultCacheExpiration"/></remarks>
    public static T GetOrStore<T>( this Cache cache, string key, T obj ) {
        return cache.GetOrStore( key, obj, DefaultCacheExpiration );
    }

    /// <summary>
    /// Allows Caching of typed data
    /// </summary>
    /// <example><![CDATA[
    /// var user = HttpRuntime
    ///   .Cache
    ///   .GetOrStore<User>(
    ///      string.Format("User{0}", _userId), 
    ///      () => Repository.GetUser(_userId));
    ///
    /// ]]></example>
    /// <typeparam name="T"></typeparam>
    /// <param name="cache">calling object</param>
    /// <param name="key">Cache key</param>
    /// <param name="obj">Object to store in cache</param>
    /// <param name="expireInMinutes">Time to expire cache in minutes</param>
    /// <returns></returns>
    public static T GetOrStore<T>( this Cache cache, string key, T obj, double expireInMinutes ) {
        var result = cache[key];

        if ( result == null ) {

            lock ( sync ) {
                result = cache[key];
                if ( result == null ) {
                    result = obj != null ? obj : default( T );
                    cache.Insert( key, result, null, DateTime.Now.AddMinutes( expireInMinutes ), Cache.NoSlidingExpiration );
                }
            }
        }

        return (T)result;

    }

}

我还要考虑进一步实现一个扩展 System.Web.HttpSessionStateBase 抽象类的可测试的 Session 解决方案。

public static class SessionExtension
{
    /// <summary>
    /// 
    /// </summary>
    /// <example><![CDATA[
    /// var user = HttpContext
    ///   .Session
    ///   .GetOrStore<User>(
    ///      string.Format("User{0}", _userId), 
    ///      () => Repository.GetUser(_userId));
    ///
    /// ]]></example>
    /// <typeparam name="T"></typeparam>
    /// <param name="cache"></param>
    /// <param name="key"></param>
    /// <param name="generator"></param>
    /// <returns></returns>
    public static T GetOrStore<T>( this HttpSessionStateBase session, string name, Func<T> generator ) {

        var result = session[name];
        if ( result != null )
            return (T)result;

        result = generator != null ? generator() : default( T );
        session.Add( name, result );
        return (T)result;
    }

}

回复于 2024-05-02T12:13:04+08:00

6
如果您希望缓存请求的长度，请将其放在控制器基类中：
```
public User User {
    get {
        User _user = ControllerContext.HttpContext.Items["user"] as User;

        if (_user == null) {
            _user = _repository.Get<User>(id);
            ControllerContext.HttpContext.Items["user"] = _user;
        }

        return _user;
    }
}
```
如果要缓存更长时间，请使用将 ControllerContext 调用替换为 Cache [14]。如果您确实选择使用 Cache 对象进行更长时间的缓存，则需要使用唯一的缓存键，因为它将在 requests/users 之间共享。
回复于 2024-05-02T12:13:04+08:00
3

我喜欢隐藏数据缓存在存储库中的事实。您可以通过 HttpContext.Current.Cache 属性访问缓存，并使用“User”id.ToString()作为密钥存储用户信息。

这意味着对存储库中的用户数据的所有访问都将使用缓存数据(如果可用)，并且不需要在模型，控制器或视图中更改代码。

我已经使用此方法来纠正系统上的严重性能问题，该系统正在查询每个 User 属性的数据库，并将页面加载时间从几分钟减少到单位数秒。

回复于 2024-05-02T12:13:04+08:00

@njappboy：很好的实施。我只会将Generator( )调用推迟到最后一个负责任的时刻。因此您也可以缓存方法调用。

/// <summary>
/// Allows Caching of typed data
/// </summary>
/// <example><![CDATA[
/// var user = HttpRuntime
///   .Cache
///   .GetOrStore<User>(
///      string.Format("User{0}", _userId), 
///      () => Repository.GetUser(_userId));
///
/// ]]></example>
/// <typeparam name="T"></typeparam>
/// <param name="Cache">calling object</param>
/// <param name="Key">Cache key</param>
/// <param name="Generator">Func that returns the object to store in cache</param>
/// <returns></returns>
/// <remarks>Uses a default cache expiration period as defined in <see cref="CacheExtensions.DefaultCacheExpiration"/></remarks>
public static T GetOrStore<T>( this Cache Cache, string Key, Func<T> Generator )
{
    return Cache.GetOrStore( Key, Generator, DefaultCacheExpiration );
}

/// <summary>
/// Allows Caching of typed data
/// </summary>
/// <example><![CDATA[
/// var user = HttpRuntime
///   .Cache
///   .GetOrStore<User>(
///      string.Format("User{0}", _userId), 
///      () => Repository.GetUser(_userId));
///
/// ]]></example>
/// <typeparam name="T"></typeparam>
/// <param name="Cache">calling object</param>
/// <param name="Key">Cache key</param>
/// <param name="Generator">Func that returns the object to store in cache</param>
/// <param name="ExpireInMinutes">Time to expire cache in minutes</param>
/// <returns></returns>
public static T GetOrStore<T>( this Cache Cache, string Key, Func<T> Generator, double ExpireInMinutes )
{
    var Result = Cache [ Key ];

    if( Result == null )
    {
        lock( Sync )
        {
            if( Result == null )
            {
                Result = Generator( );
                Cache.Insert( Key, Result, null, DateTime.Now.AddMinutes( ExpireInMinutes ), Cache.NoSlidingExpiration );
            }
        }
    }

    return ( T ) Result;
}

回复于 2024-05-02T12:13:04+08:00

这里的其他几个答案不涉及以下内容：

缓存踩踏事件
双重检查锁定

这可能导致生成器(可能需要很长时间)在不同的线程中运行多次。

这是我的版本不应该遇到这个问题：

// using System;
// using System.Web.Caching;

// https://stackoverflow.com/a/42443437
// Usage: HttpRuntime.Cache.GetOrStore("myKey", () => GetSomethingToCache());

public static class CacheExtensions
{
    private static readonly object sync = new object();
    private static TimeSpan defaultExpire = TimeSpan.FromMinutes(20);

    public static T GetOrStore<T>(this Cache cache, string key, Func<T> generator) =>
        cache.GetOrStore(key, generator, defaultExpire);

    public static T GetOrStore<T>(this Cache cache, string key, Func<T> generator, TimeSpan expire)
    {
        var result = cache[key];
        if (result == null)
        {
            lock (sync)
            {
                result = cache[key];
                if (result == null)
                {
                    result = generator();
                    cache.Insert(key, result, null, DateTime.Now.AddMinutes(expire.TotalMinutes), Cache.NoSlidingExpiration);
                }
            }
        }
        return (T)result;
    }
}

回复于 2024-05-02T12:13:04+08:00

2

如果您不需要 ASP.NET 缓存的特定失效功能，静态字段非常好，轻量级且易于使用。但是，只要您需要高级功能，就可以切换到 ASP.NET 的Cache对象进行存储。

我使用的方法是创建属性和private字段。如果该字段为null，则该属性将填充并返回该字段。我还提供了一个InvalidateCache方法，手动将字段设置为null。这种方法的优点是缓存机制封装在属性中，如果需要，可以切换到不同的方法。

回复于 2024-05-02T12:13:04+08:00

使用最小的缓存锁定实现。存储在缓存中的值包装在容器中。如果该值不在缓存中，则值容器将被锁定。仅在创建容器期间锁定缓存。

public static class CacheExtensions
{
    private static object sync = new object();

    private class Container<T>
    {
        public T Value;
    }

    public static TValue GetOrStore<TValue>(this Cache cache, string key, Func<TValue> create, TimeSpan slidingExpiration)
    {
        return cache.GetOrStore(key, create, Cache.NoAbsoluteExpiration, slidingExpiration);
    }

    public static TValue GetOrStore<TValue>(this Cache cache, string key, Func<TValue> create, DateTime absoluteExpiration)
    {
        return cache.GetOrStore(key, create, absoluteExpiration, Cache.NoSlidingExpiration);
    }

    public static TValue GetOrStore<TValue>(this Cache cache, string key, Func<TValue> create, DateTime absoluteExpiration, TimeSpan slidingExpiration)
    {
        return cache.GetOrCreate(key, x => create());
    }

    public static TValue GetOrStore<TValue>(this Cache cache, string key, Func<string, TValue> create, DateTime absoluteExpiration, TimeSpan slidingExpiration)
    {
        var instance = cache.GetOrStoreContainer<TValue>(key, absoluteExpiration, slidingExpiration);
        if (instance.Value == null)
            lock (instance)
                if (instance.Value == null)
                    instance.Value = create(key);

        return instance.Value;
    }

    private static Container<TValue> GetOrStoreContainer<TValue>(this Cache cache, string key, DateTime absoluteExpiration, TimeSpan slidingExpiration)
    {
        var instance = cache[key];
        if (instance == null)
            lock (cache)
            {
                instance = cache[key];
                if (instance == null)
                {
                    instance = new Container<TValue>();

                    cache.Add(key, instance, null, absoluteExpiration, slidingExpiration, CacheItemPriority.Default, null);
                }
            }

        return (Container<TValue>)instance;
    }
}

回复于 2024-05-02T12:13:04+08:00

如何在 ASP.NET MVC 中缓存对象？

8 回答

相关问题