C# 代理应用 - Cachable
放心，这次不是说设计模式中的代理模式，说的是C#的RealProxy的用法，主要用于：通过给class贴标签，让class做更多的工作，比如判断是否存在缓存，有则直接返回缓存object，没有则保存为缓存，等待下次请求是可以更快的获取数据（当然这只是其中一种常用用途，MVC的Action就是采用这种方式）
下面是序列图：
.Net Object Generation interceptor属于.NET自身行为，不需要额外写代码。
Code Consumer指想调用RealObject来进行调用的对象，比如控制台程序，或者WEB程序。
ProxyAttribute里定义了具体代理类是哪个，这个代理类是自己 继承RealProxy写的一个代理类，这个类中需要加入前置、后置、环绕等方法（具体根据需求）
下面我们来看具体如何在.Net中实现：
public class FollowAction
{
public bool StopExecute { get; set; } //用于在前置方法中，指示是否停止执行真正的方法体，比如已经找到了cache value，因此不需要继续运行方法体的情况
public object Result { get; set; } //保存cache value的变量
} public abstract class CachableRealProxy : RealProxy
{
private MarshalByRefObject target; public MyAOPRealProxy(Type objType, MarshalByRefObject obj)
: base(objType)
{
target = obj;
} public override IMessage Invoke(IMessage msg)
{
IMessage retMsg = null;
IMethodCallMessage methodCall = (IMethodCallMessage)msg;
IMethodReturnMessage methodReturn = null;
object[] copiedArgs = Array.CreateInstance(typeof(object), methodCall.Args.Length) as object[];
methodCall.Args.CopyTo(copiedArgs, 0);
if (msg is IConstructionCallMessage)
{ IConstructionCallMessage ccm = (IConstructionCallMessage)msg;
RemotingServices.GetRealProxy(target).InitializeServerObject(ccm);
ObjRef oRef = RemotingServices.Marshal(target);
RemotingServices.Unmarshal(oRef);
retMsg = EnterpriseServicesHelper.CreateConstructionReturnMessage(ccm, (MarshalByRefObject)this.GetTransparentProxy()); }
else
{
bool aopAttributeExists = false;
object[] attrs = methodCall.MethodBase.GetCustomAttributes(false);
if (attrs != null && attrs.Count() > 0)
{
foreach(object o in attrs)
{
CachableAttribute attr = o as CachableAttribute;
if (attr != null)
{
aopAttributeExists = true;
break;
}
}
}
FollowAction follow=null;
if (aopAttributeExists)
follow = this.PreProcess(msg); try
{
object returnValue = null;
if (follow != null && follow.StopExecute)
returnValue = follow.Result;
else
returnValue = methodCall.MethodBase.Invoke(this.target, copiedArgs);
methodReturn = new ReturnMessage(returnValue, copiedArgs, copiedArgs.Length, methodCall.LogicalCallContext, methodCall); if (follow == null || !follow.StopExecute)
if (aopAttributeExists)
this.PostProcess(msg, methodReturn);
}
catch (Exception ex)
{
if (null != ex.InnerException)
{
methodReturn = new ReturnMessage(ex.InnerException, methodCall);
}
else
{
methodReturn = new ReturnMessage(ex, methodCall);
}
}
retMsg = methodReturn; }
return retMsg;
} public override FollowAction PreProcess(System.Runtime.Remoting.Messaging.IMessage requestMsg) //处理前置方法
{
bool cacheDefinationTagExists = true;
CachableAttribute cacheDefine = CheckCacheDefinationTag(requestMsg, ref cacheDefinationTagExists);
if (!cacheDefinationTagExists)
return null; string cacheKey = cacheDefine.GenerateCacheKey();
object o=CacheManager.Instance().GetCacheCore().Get(cacheDefine.Location, cacheKey);
if (o != null)
{
FollowAction follow = new FollowAction();
follow.Result = o;
follow.StopExecute = true;
return follow;
} return null;
} public override void PostProcess(System.Runtime.Remoting.Messaging.IMessage requestMsg, System.Runtime.Remoting.Messaging.IMessage responseMsg)//处理后置方法
{
bool cacheDefinationTagExists = true;
CachableAttribute cacheDefine = CheckCacheDefinationTag(requestMsg, ref cacheDefinationTagExists);
if (!cacheDefinationTagExists)
return; ReturnMessage returnMsg = (ReturnMessage)responseMsg; string cacheKey = cacheDefine.GenerateCacheKey();
CacheManager.Instance().GetCacheCore().Set(cacheDefine.Location, cacheKey, returnMsg.ReturnValue);
}
private static CachableAttribute CheckCacheDefinationTag(System.Runtime.Remoting.Messaging.IMessage requestMsg, ref bool cacheDefinationTagExists)//Help函数
{
IMethodCallMessage methodCall = (IMethodCallMessage)requestMsg;
object[] attrs = methodCall.MethodBase.GetCustomAttributes(typeof(CachableAttribute), false);
if (attrs == null || attrs.Count() <= 0)
cacheDefinationTagExists = false;
CachableAttribute cacheDefine = attrs[0] as CachableAttribute;
if (cacheDefine == null)
cacheDefinationTagExists = false;
return cacheDefine;
}
}
还需要2个Attribute: 如上代码中用到的CachableAttribute和CachableEnabledAttribute
CachableAttribute用来贴在各个函数签名上，可以指定cache的key等信息（继承自普通的Attribute）
CachableEnabledAttribute用来关联 自定义proxy以及需要被代理的class的，用法是贴在被代理的class签名上（继承自ProxyAttribute）
代码如下：
public class CachableAttribute : Attribute
{
public string Location { get; set; }
public string Key { get; set; }
public CacheAction CacheAction { get; set; }
public string KeyPath { get; set; }
public object CacheObject { get; set; }
public TimeSpan ExpireTimeSpan { get; set; }
public DateTime AbsoluteExpireTime { get; set; } public string GenerateCacheKey()
{
//will be changed
return string.Format("{0}", this.Key);
}
}
public class CachableEnabledAttribute : ProxyAttribute
{
public override MarshalByRefObject CreateInstance(Type serverType)
{
MarshalByRefObject target = base.CreateInstance(serverType);
CachableRealProxy rp = new CachableRealProxy(serverType, target);
MarshalByRefObject obj = (MarshalByRefObject)rp.GetTransparentProxy();
return obj;
}
}
被代理的class需要继承自ContextBoundObject
[CachableEnabled()]
public class RealObject : ContextBoundObject
{
[Cachable(Location = "OrdersQuery", CacheAction = CacheAction.Read, Key = "OrderQueryService_QueryByFirstName_{0}")]
public override QueryResult<QueryDto.OrderDto> QueryByFirstName(string firstName, PagingInfo pgInfo)
{
QueryResult<QueryDto.OrderDto> lst = new QueryResult<QueryDto.OrderDto>();
lst.List = new List<QueryDto.OrderDto>();
lst.TotalCount = 1000;
for (int i = 0; i < 1;i++ )
{
OrderDto o = new OrderDto();
o.BuyWhat = string.Format("Buywhat {0}", DateTime.Now.ToString());
o.FirstName = string.Format("FirstName {0}", DateTime.Now.ToString());
o.LastName = string.Format("LastName {0}", DateTime.Now.ToString());
o.Email = string.Format("Email {0}", DateTime.Now.ToString());
o.OrderID = Guid.NewGuid();
lst.List.Add(o);
}
return lst;
}
}
看下控制台测试代码：
RealObject srv1 = new RealObject();
while (true)
{
Thread.Sleep(1000); //每隔1s执行调用，看看返回的时间是否相同，相同则代表已经是cachable的了
QueryResult<OrderDto> lst = srv1.QueryByFirstName("aaron", new CoreFramework.QueryService.PagingInfo() { PageIndex = 0, PageSize = 10, OrderByColumn = "FirstName", IsAscendingSort = true });
foreach (OrderDto order in lst.List)
{
string msg = string.Format("{0}-{1}-{2}-{3}", order.OrderID, order.FirstName, order.LastName, order.BuyWhat);
Console.WriteLine(msg);
}
}
运行效果图：
搞定。
自省推动进步，视野决定未来。
心怀远大理想。
为了家庭幸福而努力。
用A2D科技，服务社会。
心怀远大理想。
为了家庭幸福而努力。
用A2D科技，服务社会。