Java：多个自刷新缓存对象(Java: multiple self refreshing cache object)

Java：多个自刷新缓存对象(Java: multiple self refreshing cache object)

我想创建一个带有工厂的缓存对象，用于多个表。 每个缓存都有自己的生命周期，这些生命周期彼此不同。 例如，City对象的生命周期约为一年，设施列表对象的生命周期约为1天。

这是我的缓存类

public abstract class CacheAbstract<E, I, C> { private Long timestamp; private Class<E> entityClass; private Class<I> idClass; private Class<C> cacheClass; protected Integer TTL = 60; // In minutes. defaults to 60 mins private Map<I, C> cache; private Timer timer; public CacheAbstract(Class<E> entityClass, Class<I> idClass, Class<C> cacheClass) { this.entityClass = entityClass; this.idClass = idClass; this.cacheClass = cacheClass; } public Boolean isExpired() { return (this.timestamp + TTL * 60000) < new Date().getTime(); } private void verifyCache() { if (this.cache == null || isExpired()) { this.load(); } } private void onTimer() { this.timer = new Timer(); timer.schedule(new TimerTask() { @Override public void run() { throw new UnsupportedOperationException("Not supported yet."); //What should I do here? I can't call this class' load(), can I?; } }, this.TTL * 60000); } public void load() { // Load all data here this.timestamp = new Date().getTime(); } public C get(I id) { this.verifyCache(); return this.cache.get(id); } public List<C> getAll() { this.verifyCache(); List<C> list = new ArrayList<>(this.cache.values()); return list; } protected abstract C transform(E entity); protected abstract I getID(E entity); public abstract String getName(); }

这个类不是单例，而是由工厂实例化的，比方说，CacheFactory

public final class CacheFactory { private Map<String, CacheAbstract> caches; private CacheFactory() { } public void registerCache(CacheAbstract cache) { if (caches == null) { caches = new HashMap<>(); } if (caches.containsKey(cache.getName())) { this.caches.get(cache.getName()).load(); } else { this.caches.put(cache.getName(), cache); } } public CacheAbstract getCache(String name) throws ExceptionInvalidCacheName { if (caches.containsKey(name)) { return caches.get(name); } else { throw new ExceptionInvalidCacheName("KOLOM SERVER [cache]: Cache '" + name + "' not registered"); } } public Boolean isExist(String name) { return caches.containsKey(name); } public List<String> getNames() { return new ArrayList<>(caches.keySet()); } public static CacheFactory getInstance() { return CacheFactoryHolder.INSTANCE; } private static class CacheFactoryHolder { private static final CacheFactory INSTANCE = new CacheFactory(); } }

现在，我如何实现算法让CacheAbstract在需要时刷新自己？

I would like create a cache object with a factory, for a multiple tables. Each cache has their own life time which are different to one another. For example, lifetime for City object is about a year, and lifetime for facility list object is about 1 day.

This below is my cache class

public abstract class CacheAbstract<E, I, C> { private Long timestamp; private Class<E> entityClass; private Class<I> idClass; private Class<C> cacheClass; protected Integer TTL = 60; // In minutes. defaults to 60 mins private Map<I, C> cache; private Timer timer; public CacheAbstract(Class<E> entityClass, Class<I> idClass, Class<C> cacheClass) { this.entityClass = entityClass; this.idClass = idClass; this.cacheClass = cacheClass; } public Boolean isExpired() { return (this.timestamp + TTL * 60000) < new Date().getTime(); } private void verifyCache() { if (this.cache == null || isExpired()) { this.load(); } } private void onTimer() { this.timer = new Timer(); timer.schedule(new TimerTask() { @Override public void run() { throw new UnsupportedOperationException("Not supported yet."); //What should I do here? I can't call this class' load(), can I?; } }, this.TTL * 60000); } public void load() { // Load all data here this.timestamp = new Date().getTime(); } public C get(I id) { this.verifyCache(); return this.cache.get(id); } public List<C> getAll() { this.verifyCache(); List<C> list = new ArrayList<>(this.cache.values()); return list; } protected abstract C transform(E entity); protected abstract I getID(E entity); public abstract String getName(); }

this class is not a singleton, and will be instantiated by a factory., let's say, CacheFactory

public final class CacheFactory { private Map<String, CacheAbstract> caches; private CacheFactory() { } public void registerCache(CacheAbstract cache) { if (caches == null) { caches = new HashMap<>(); } if (caches.containsKey(cache.getName())) { this.caches.get(cache.getName()).load(); } else { this.caches.put(cache.getName(), cache); } } public CacheAbstract getCache(String name) throws ExceptionInvalidCacheName { if (caches.containsKey(name)) { return caches.get(name); } else { throw new ExceptionInvalidCacheName("KOLOM SERVER [cache]: Cache '" + name + "' not registered"); } } public Boolean isExist(String name) { return caches.containsKey(name); } public List<String> getNames() { return new ArrayList<>(caches.keySet()); } public static CacheFactory getInstance() { return CacheFactoryHolder.INSTANCE; } private static class CacheFactoryHolder { private static final CacheFactory INSTANCE = new CacheFactory(); } }

Now, how I can implement algorithm to let CacheAbstract to refresh itself when needed?

最满意答案

是的，你可以简单地调用load() ：

private void onTimer() { timer = new Timer(); timer.schedule(new TimerTask() { @Override public void run() { load(); // Call the containing class method } }, TTL * 60000); }

因为每个匿名类实际上也是一个内部类，所以它引用了声明它的包含类。

但是，如果你真的想要主动过期，你只会使用一个Timer。 由于在每次调用get()都调用了verifyCache() ，因此您已经有了延迟到期。 也许这足以满足您的需求。

Yes, you can simply call load():

private void onTimer() { timer = new Timer(); timer.schedule(new TimerTask() { @Override public void run() { load(); // Call the containing class method } }, TTL * 60000); }

because every anonymous class is actually also an inner class, so it has a reference to the containing class that declares it.

But, you would only use a Timer if you really wanted active expiration. You already have lazy expiration due to the call to verifyCache() in every call to get(). Maybe that's enough for your needs now.