Java Cache详解及简单实现

public interface Cache {
  /**
  * Refresh the cache. If succeed, return true, else return false;
  * 
  * @return
  */
  boolean refresh();

  /**
  * How much time it will refresh the cache.
  * 
  * @return
  */
  long interval();
}

@Controller
public class CacheManagerController {

  @Autowired
  private CacheController cache;

  private static ScheduledExecutorService executor = Executors
     .newScheduledThreadPool(1);

  public CacheManagerController() {
   executor.scheduleAtFixedRate(() -> cache.refresh(), 0, cache.interval(),
      TimeUnit.MILLISECONDS);
  }
}

public class CacheService {
  public static final long ONE_MINUTE = 60 * 1000;

  private static ScheduledExecutorService executor = Executors
     .newScheduledThreadPool(1);

  public static void register(Cache cache) {
   executor.scheduleAtFixedRate(() -> cache.refresh(), 0, cache.interval(),
      TimeUnit.MILLISECONDS);
  }
}

@Controller
public class CacheController implements Cache {

  // autowire 各种不同的service，或者是repo连接数据库
  @Autowired
  private Service service;

  public CacheController() {
   CacheService.register(this);
  }

  // cache interface
  @Override
  public long interval() {
   return 1000;
  }

  @Override
  public boolean refresh() {
   return true;
  }
}

public class PreloadListener implements ServletContextListener {
  @Override
  public void contextInitialized(ServletContextEvent servletContextEvent) {
   CacheFactory.init();
  }

  @Override
  public void contextDestroyed(ServletContextEvent servletContextEvent) {

  }
}

// web.xml
  <listener>
    <listener-class>com.sapphire.listener.PreloadListener</listener-class>
  </listener>

public class CacheFactory {
  private static ConcurrentHashMap<String, Cache> caches = new ConcurrentHashMap<>();
  private static ScheduledExecutorService executorService = Executors.newScheduledThreadPool(1);

  private static void register(Cache cache) {
   caches.put(cache.category(), cache);
  }

  private static void registerAll() {
   register(new StockCache());
  }

  public static void init() {
   registerAll();

   for (Cache cache : caches.values()) {
     executorService.scheduleAtFixedRate(new Runnable() {
      @Override
      public void run() {
        cache.refresh();
      }
     }, 0, cache.interval(), TimeUnit.MILLISECONDS);
   }
  }

  public static Cache getCache(String key) {
   if (caches.contains(key)) {
     return caches.get(key);
   }
   return null;
  }
}

// cache接口除了需要提供interval和refresh以外，还需要提供一个category来区分不同的Cache
public interface Cache {
  /**
  * Refresh the cache. If succeed, return true, else return false;
  * 
  * @return
  */
  boolean refresh();

  /**
  * How much time it will refresh the cache.
  * 
  * @return
  */
  long interval();

  /**
  * Cache's category. Each cache has distinct category.
  * 
  * @return
  */
  String category();
}