My .NET ICache
Aug 24, 2010
UPDATE: I posted the code on github: http://github.com/karlseguin/Metsys.Caching
In my last post on design and testability, some questions were raised about the ICache interface I was using. This is going to be a code heavy post - largely meant to be copy and pasted. If you don't understand it, don't use it.
The API is meant to remove some of the repetition that comes from using a cache, by making use of my very good friends Action and Func.
First, the interface:
using System;
using System.Web.Caching;
public interface ICache
{
T Get<T>(string key, params object[] keyArgs);
T Fetch<T>(string key, Func<T> callIfGetReturnsNull, params object[] keyArgs);
T Fetch<T>(string key, Func<T> callIfGetReturnsNull, DateTime absoluteExpiration, params object[] keyArgs);
T Fetch<T>(string key, Func<T> callIfGetReturnsNull, TimeSpan slidingExpiration, params object[] keyArgs);
T Fetch<T>(string key, Func<T> callIfGetReturnsNull, CacheDependency dependencies, params object[] keyArgs);
T Fetch<T>(string key, Func<T> callIfGetReturnsNull, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, params object[] keyArgs);
T Fetch<T>(string key, Func<T> callIfGetReturnsNull, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback, params object[] keyArgs);
T Fetch<T>(string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, params object[] keyArgs);
T Fetch<T>(string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, DateTime absoluteExpiration, params object[] keyArgs);
T Fetch<T>(string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, TimeSpan slidingExpiration, params object[] keyArgs);
T Fetch<T>(string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, CacheDependency dependencies, params object[] keyArgs);
T Fetch<T>(string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, params object[] keyArgs);
T Fetch<T>(string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback, params object[] keyArgs);
void Insert(string key, object data, params object[] keyArgs);
void Insert(string key, object data, DateTime absoluteExpiration, params object[] keyArgs);
void Insert(string key, object data, TimeSpan slidingExpiration, params object[] keyArgs);
void Insert(string key, object data, CacheDependency dependencies, params object[] keyArgs);
void Insert(string key, object data, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, params object[] keyArgs);
void Insert(string key, object data, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback, params object[] keyArgs);
void Remove(string key, params object[] keyArgs);
void RemoveAll();
int Count();
}Next we beef up the System.Web.Caching.Cache class with extension methods so that it can do what we need it to:
using System;
using System.Web.Caching;
public static class CacheExtensions
{
public static T Get<T>(this Cache cache, string key, params object[] keyArgs)
{
return (T)cache.Get(BuildKey(key, keyArgs));
}
public static T Fetch<T>(this Cache cache, string key, Func<T> callIfGetReturnsNull, params object[] keyArgs)
{
return cache.Fetch(key, null, callIfGetReturnsNull, keyArgs);
}
public static T Fetch<T>(this Cache cache, string key, Func<T> callIfGetReturnsNull, DateTime absoluteExpiration, params object[] keyArgs)
{
return cache.Fetch(key, null, callIfGetReturnsNull, absoluteExpiration, keyArgs);
}
public static T Fetch<T>(this Cache cache, string key, Func<T> callIfGetReturnsNull, TimeSpan slidingExpiration, params object[] keyArgs)
{
return cache.Fetch(key, null, callIfGetReturnsNull, slidingExpiration, keyArgs);
}
public static T Fetch<T>(this Cache cache, string key, Func<T> callIfGetReturnsNull, CacheDependency dependencies, params object[] keyArgs)
{
return cache.Fetch(key, null, callIfGetReturnsNull, dependencies, keyArgs);
}
public static T Fetch<T>(this Cache cache, string key, Func<T> callIfGetReturnsNull, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, params object[] keyArgs)
{
return cache.Fetch(key, null, callIfGetReturnsNull, dependencies, absoluteExpiration, slidingExpiration, keyArgs);
}
public static T Fetch<T>(this Cache cache, string key, Func<T> callIfGetReturnsNull, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback, params object[] keyArgs)
{
return cache.Fetch(key, null, callIfGetReturnsNull, dependencies, absoluteExpiration, slidingExpiration, priority, onRemoveCallback, keyArgs);
}
public static T Fetch<T>(this Cache cache, string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, params object[] keyArgs)
{
var item = (T)cache.Get(BuildKey(key, keyArgs));
if (item == null)
{
item = callIfGetReturnsNull();
cache.Insert(key, item, keyArgs);
}
else if (callIfGetReturnsValue != null)
{
callIfGetReturnsValue(item);
}
return item;
}
public static T Fetch<T>(this Cache cache, string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, DateTime absoluteExpiration, params object[] keyArgs)
{
var item = cache.Get(BuildKey(key, keyArgs));
if (item == null)
{
item = callIfGetReturnsNull();
cache.Insert(key, item, absoluteExpiration, keyArgs);
return (T)item;
}
if (callIfGetReturnsValue != null)
{
callIfGetReturnsValue((T)item);
}
return (T)item;
}
public static T Fetch<T>(this Cache cache, string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, TimeSpan slidingExpiration, params object[] keyArgs)
{
var item = (T)cache.Get(BuildKey(key, keyArgs));
if (item == null)
{
item = callIfGetReturnsNull();
cache.Insert(key, item, slidingExpiration, keyArgs);
}
else if (callIfGetReturnsValue != null)
{
callIfGetReturnsValue(item);
}
return item;
}
public static T Fetch<T>(this Cache cache, string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, CacheDependency dependencies, params object[] keyArgs)
{
var item = (T)cache.Get(BuildKey(key, keyArgs));
if (item == null)
{
item = callIfGetReturnsNull();
cache.Insert(key, item, dependencies, keyArgs);
}
else if (callIfGetReturnsValue != null)
{
callIfGetReturnsValue(item);
}
return item;
}
public static T Fetch<T>(this Cache cache, string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, params object[] keyArgs)
{
var item = (T)cache.Get(BuildKey(key, keyArgs));
if (item == null)
{
item = callIfGetReturnsNull();
cache.Insert(key, item, dependencies, absoluteExpiration, slidingExpiration, keyArgs);
}
else if (callIfGetReturnsValue != null)
{
callIfGetReturnsValue(item);
}
return item;
}
public static T Fetch<T>(this Cache cache, string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback, params object[] keyArgs)
{
var item = (T)cache.Get(BuildKey(key, keyArgs));
if (item == null)
{
item = callIfGetReturnsNull();
cache.Insert(key, item, dependencies, absoluteExpiration, slidingExpiration, priority, onRemoveCallback, keyArgs);
}
else if (callIfGetReturnsValue != null)
{
callIfGetReturnsValue(item);
}
return item;
}
public static void Insert(this Cache cache, string key, object data, params object[] keyArgs)
{
if (data != null)
{
cache.Insert(BuildKey(key, keyArgs), data);
}
}
public static void Insert(this Cache cache, string key, object data, DateTime absoluteExpiration, params object[] keyArgs)
{
if (data != null)
{
cache.Insert(BuildKey(key, keyArgs), data, null, absoluteExpiration, Cache.NoSlidingExpiration);
}
}
public static void Insert(this Cache cache, string key, object data, TimeSpan slidingExpiration, params object[] keyArgs)
{
if (data != null)
{
cache.Insert(BuildKey(key, keyArgs), data, null, Cache.NoAbsoluteExpiration, slidingExpiration);
}
}
public static void Insert(this Cache cache, string key, object data, CacheDependency dependencies, params object[] keyArgs)
{
if (data != null)
{
cache.Insert(BuildKey(key, keyArgs), data, dependencies);
}
}
public static void Insert(this Cache cache, string key, object data, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, params object[] keyArgs)
{
if (data != null)
{
cache.Insert(BuildKey(key, keyArgs), data, dependencies, absoluteExpiration, slidingExpiration);
}
}
public static void Insert(this Cache cache, string key, object data, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback, params object[] keyArgs)
{
if (data != null)
{
cache.Insert(BuildKey(key, keyArgs), data, dependencies, absoluteExpiration, slidingExpiration, priority, onRemoveCallback);
}
}
public static void Remove(this Cache cache, string key, params object[] keyArgs)
{
cache.Remove(BuildKey(key, keyArgs));
}
public static void RemoveAll(this Cache cache)
{
var enumerator = cache.GetEnumerator();
while (enumerator.MoveNext())
{
cache.Remove((string)enumerator.Key);
}
}
private static string BuildKey(string key, params object[] keyArgs)
{
return (keyArgs == null || keyArgs.Length == 0) ? key : string.Format(key, keyArgs);
}
}Now we wrap the actual System.Web.Caching.Cache class in a wrapper which implements our interface:
using System;
using System.Web;
using System.Web.Caching;
public sealed class InMemoryCache : ICache
{
public T Get<T>(string key, params object[] keyArgs)
{
return HttpRuntime.Cache.Get<T>(key, keyArgs);
}
public T Fetch<T>(string key, Func<T> callIfGetReturnsNull, params object[] keyArgs)
{
return HttpRuntime.Cache.Fetch(key, callIfGetReturnsNull, keyArgs);
}
public T Fetch<T>(string key, Func<T> callIfGetReturnsNull, DateTime absoluteExpiration, params object[] keyArgs)
{
return HttpRuntime.Cache.Fetch(key, callIfGetReturnsNull, absoluteExpiration, keyArgs);
}
public T Fetch<T>(string key, Func<T> callIfGetReturnsNull, TimeSpan slidingExpiration, params object[] keyArgs)
{
return HttpRuntime.Cache.Fetch(key, callIfGetReturnsNull, slidingExpiration, keyArgs);
}
public T Fetch<T>(string key, Func<T> callIfGetReturnsNull, CacheDependency dependencies, params object[] keyArgs)
{
return HttpRuntime.Cache.Fetch(key, callIfGetReturnsNull, dependencies, keyArgs);
}
public T Fetch<T>(string key, Func<T> callIfGetReturnsNull, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, params object[] keyArgs)
{
return HttpRuntime.Cache.Fetch(key, callIfGetReturnsNull, dependencies, absoluteExpiration, slidingExpiration, keyArgs);
}
public T Fetch<T>(string key, Func<T> callIfGetReturnsNull, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback, params object[] keyArgs)
{
return HttpRuntime.Cache.Fetch(key, callIfGetReturnsNull, dependencies, absoluteExpiration, slidingExpiration, priority, onRemoveCallback, keyArgs);
}
public T Fetch<T>(string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, params object[] keyArgs)
{
return HttpRuntime.Cache.Fetch(key, callIfGetReturnsValue, callIfGetReturnsNull, keyArgs);
}
public T Fetch<T>(string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, DateTime absoluteExpiration, params object[] keyArgs)
{
return HttpRuntime.Cache.Fetch(key, callIfGetReturnsValue, callIfGetReturnsNull, absoluteExpiration, keyArgs);
}
public T Fetch<T>(string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, TimeSpan slidingExpiration, params object[] keyArgs)
{
return HttpRuntime.Cache.Fetch(key, callIfGetReturnsValue, callIfGetReturnsNull, slidingExpiration, keyArgs);
}
public T Fetch<T>(string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, CacheDependency dependencies, params object[] keyArgs)
{
return HttpRuntime.Cache.Fetch(key, callIfGetReturnsValue, callIfGetReturnsNull, dependencies, keyArgs);
}
public T Fetch<T>(string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, params object[] keyArgs)
{
return HttpRuntime.Cache.Fetch(key, callIfGetReturnsValue, callIfGetReturnsNull, dependencies, absoluteExpiration, slidingExpiration, keyArgs);
}
public T Fetch<T>(string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback, params object[] keyArgs)
{
return HttpRuntime.Cache.Fetch(key, callIfGetReturnsValue, callIfGetReturnsNull, dependencies, absoluteExpiration, slidingExpiration, priority, onRemoveCallback, keyArgs);
}
public void Insert(string key, object data, params object[] keyArgs)
{
HttpRuntime.Cache.Insert(key, data, keyArgs);
}
public void Insert(string key, object data, DateTime absoluteExpiration, params object[] keyArgs)
{
HttpRuntime.Cache.Insert(key, data, absoluteExpiration, keyArgs);
}
public void Insert(string key, object data, TimeSpan slidingExpiration, params object[] keyArgs)
{
HttpRuntime.Cache.Insert(key, data, slidingExpiration, keyArgs);
}
public void Insert(string key, object data, CacheDependency dependencies, params object[] keyArgs)
{
HttpRuntime.Cache.Insert(key, data, dependencies, keyArgs);
}
public void Insert(string key, object data, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, params object[] keyArgs)
{
HttpRuntime.Cache.Insert(key, data, dependencies, absoluteExpiration, slidingExpiration, keyArgs);
}
public void Insert(string key, object data, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback, params object[] keyArgs)
{
HttpRuntime.Cache.Insert(key, data, dependencies, absoluteExpiration, slidingExpiration, priority, onRemoveCallback, keyArgs);
}
public void Remove(string key, params object[] keyArgs)
{
HttpRuntime.Cache.Remove(key, keyArgs);
}
public void RemoveAll()
{
HttpRuntime.Cache.RemoveAll();
}
public int Count()
{
return HttpRuntime.Cache.Count;
}
}Finally, we need a no-cache solution. This is useful in a number of cases, such as development, and easy testing - when testing, you often don't even need a mock, you just want to circumvent the cache mechanism:
using System;
using System.Web.Caching;
public class NoCache : ICache
{
public T Get<T>(string key, params object[] keyArgs)
{
return default(T);
}
public T Fetch<T>(string key, Func<T> callIfGetReturnsNull, params object[] keyArgs)
{
return callIfGetReturnsNull();
}
public T Fetch<T>(string key, Func<T> callIfGetReturnsNull, DateTime absoluteExpiration, params object[] keyArgs)
{
return callIfGetReturnsNull();
}
public T Fetch<T>(string key, Func<T> callIfGetReturnsNull, TimeSpan slidingExpiration, params object[] keyArgs)
{
return callIfGetReturnsNull();
}
public T Fetch<T>(string key, Func<T> callIfGetReturnsNull, CacheDependency dependencies, params object[] keyArgs)
{
return callIfGetReturnsNull();
}
public T Fetch<T>(string key, Func<T> callIfGetReturnsNull, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, params object[] keyArgs)
{
return callIfGetReturnsNull();
}
public T Fetch<T>(string key, Func<T> callIfGetReturnsNull, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback, params object[] keyArgs)
{
return callIfGetReturnsNull();
}
public T Fetch<T>(string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, params object[] keyArgs)
{
var r = callIfGetReturnsNull();
return r == null ? callIfGetReturnsNull() : r;
}
public T Fetch<T>(string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, DateTime absoluteExpiration, params object[] keyArgs)
{
var r = callIfGetReturnsNull();
return r == null ? callIfGetReturnsNull() : r;
}
public T Fetch<T>(string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, TimeSpan slidingExpiration, params object[] keyArgs)
{
var r = callIfGetReturnsNull();
return r == null ? callIfGetReturnsNull() : r;
}
public T Fetch<T>(string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, CacheDependency dependencies, params object[] keyArgs)
{
var r = callIfGetReturnsNull();
return r == null ? callIfGetReturnsNull() : r;
}
public T Fetch<T>(string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, params object[] keyArgs)
{
var r = callIfGetReturnsNull();
return r == null ? callIfGetReturnsNull() : r;
}
public T Fetch<T>(string key, Action<T> callIfGetReturnsValue, Func<T> callIfGetReturnsNull, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback, params object[] keyArgs)
{
var r = callIfGetReturnsNull();
return r == null ? callIfGetReturnsNull() : r;
}
public void Insert(string key, object data, params object[] keyArgs){}
public void Insert(string key, object data, DateTime absoluteExpiration, params object[] keyArgs) { }
public void Insert(string key, object data, TimeSpan slidingExpiration, params object[] keyArgs) { }
public void Insert(string key, object data, CacheDependency dependencies, params object[] keyArgs) { }
public void Insert(string key, object data, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, params object[] keyArgs) { }
public void Insert(string key, object data, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback, params object[] keyArgs) { }
public void Remove(string key, params object[] keyArgs) { }
public void RemoveAll() { }
public int Count()
{
return 0;
}
}That's it. Here's how you might use it in a test. You can greatly clean up the constraints by encapsulating that in a custom constraint - but I don't want to make it too easy for you.
[Fact]
public void GetsTheUserFromTheCache()
{
var user = new User();
var userId = new Guid("11c2deee-0794-4874-a581-4a75aa85eca5");
var cache = Dynamic<ICache>();
var repository = new UserRepository(cache);
cache.Expect(c => c.Fetch(Arg<string>.Is.Equal("user_{0}"), Arg<Func<User>>.Is.Anything, Arg<DateTime>.Is.Anything, Arg<object[]>.Matches(o => (Guid)o[0] == userId && o.Length == 1)))
.Return(user);
ReplayAll();
Assert.Same(user, repository.GetUser(userId));
cache.VerifyAllExpectations();
}
[Fact]
public void GetsTheUserFromTheStoreIfNotInTheCache()
{
var userId = new Guid("11c2deee-0794-4874-a581-4a75aa85eca5");
var user = new User{Id = userId, Name = "Goku", IsPowerLevelOver900 = true};
var repository = new UserRepository(new NoCache());
SomeTestDbHelper.Insert(user);
Assert.Equal(user.Id, repository.GetUser(userId).Id);
}
[Fact]
public void StoresTheUserInTheCache()
{
var userId = new Guid("11c2deee-0794-4874-a581-4a75aa85eca5");
var user = new User{Id = userId, Name = "Vegeta", IsPowerLevelOver900 = false};
var cache = new InMemoryCache();
var repository = new UserRepository(cache);
SomeTestDbHelper.Insert(user);
var expected = repository.GetUser(userId);
Assert.Same(expected, cache.Get<User>("user_{0}", user.Id));
}