java缓存

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public class WebContextCache   
{   
  
    /** 写日志 */  
    private static Log logger = LogFactory.getLog(WebContextCache.class);   
  
    private static WebContextCache instance = new WebContextCache();   
  
    /**  
	     * 初始化缓存大小  
	     */  
	    private static final int CAPACITY_NUM = 200;   
	  
	    private Map applicationMap = new ConcurrentHashMap(   
	            CAPACITY_NUM);   
	  
	    public static WebContextCache getInstance()   
	    {   
	        return instance;   
	    }   
	  
	    public static void createAppSession(String id, ApplicationSession appSession)   
	    {   
	  
	        getInstance().applicationMap.put(id, appSession);   
	        if (!getInstance().applicationMap.containsKey(id))   
	        {   
	            logger.info(id + ":cache init failure");   
	        }   
	    }   
	  
	    public static void remoteAppSession(String id)   
	    {   
	        ApplicationSession appSession = getInstance().applicationMap.remove(id);   
	        if (appSession != null)   
	        {   
	            appSession.clearApplicationSession();   
	        }   
	    }   
	  
	    public static ApplicationSession getAppSession(String id)   
	    {   
	  
	        ApplicationSession appSession = getInstance().applicationMap.get(id);   
	        if (appSession == null)   
	        {   
	            logger.info(id + ":cache space has not been inited or been removed");   
	            appSession = new ApplicationSession();   
	            WebContextCache.createAppSession(id, appSession);   
	        }   
	  
	        return appSession;   
	    }   
	}  


	Java代码  
public class ApplicationSession   
{   
/**  
     * 默认的map初始化大小  
     */  
    private static final int DEFAULT_MAP_SIZE = 100;   
  
    private final Map cache = new HashMap(DEFAULT_MAP_SIZE);   
    public Object getFromCache(Object key)   
	    {   
	        synchronized (cache)   
	        {   
	            return cache.get(key);   
	        }   
	    }   
	  
	    public void putToCache(Object key, Object value)   
	    {   
	        synchronized (cache)   
	        {   
	            cache.put(key, value);   
	        }   
	    }   
	  
	    public void removeAllCache()   
	    {   
	        synchronized (cache)   
	        {   
	            cache.clear();   
	        }   
 	}   
	       
	  
	    public void clearApplicationSession()   
	    {   
     cache.clear();   
	    }   
	  
	}  

Java代码  
public abstract class ActionSupport extends Action   
{   
    protected void putToCache(HttpServletRequest request, Object key, Object value)   
    {   
        ApplicationSession appSession = WebContextCache.getAppSession(request.getSession(true)   
                .getId());   
        appSession.putToCache(key, value);   
    }   
  
    protected Object getObjectFromCache(HttpServletRequest request, Object key)   
	    {   
	        ApplicationSession appSession = WebContextCache.getAppSession(request.getSession(true)   
	                .getId());   
	        return appSession.getFromCache(key);   
	    }   
	}