Java 中常用缓存Cache机制的实现

2016-11-03 - 894 Views - 0 Goods - Nothing

缓存主要可分为二大类:
一、通过文件缓存,顾名思义文件缓存是指把数据存储在磁盘上,不管你是以XML格式,序列化文件DAT格式还是其它文件格式;

二、内存缓存,也就是实现一个类中静态Map,对这个Map进行常规的增删查.

代码如下 :


/**
 * 
 * @ClassName: CacheManager 
 * @Description: TODO(管理缓存实现
 				可扩展的功能:当chche到内存溢出时必须清除掉最早期的一些缓存对象,
 				这就要求对每个缓存对象保存创建时间 ) 
 * @author SongLiGuo
 * @date 2016-11-3 下午5:00:58 
 *
 */
public class CacheManager {   
   private static HashMap cacheMap = new HashMap();   
   
   //单实例构造方法   
   private CacheManager() {   
       super();   
   }   
   //获取布尔值的缓存   
   public static boolean getSimpleFlag(String key){   
       try{   
           return (Boolean) cacheMap.get(key);   
       }catch(NullPointerException e){   
           return false;   
       }   
   }   
   public static long getServerStartdt(String key){   
       try {   
           return (Long)cacheMap.get(key);   
       } catch (Exception ex) {   
           return 0;   
       }   
   }   
   //设置布尔值的缓存   
   public synchronized static boolean setSimpleFlag(String key,boolean flag){   
       if (flag && getSimpleFlag(key)) {//假如为真不允许被覆盖   
           return false;   
       }else{   
           cacheMap.put(key, flag);   
           return true;   
       }   
   }   
   public synchronized static boolean setSimpleFlag(String key,long serverbegrundt){   
       if (cacheMap.get(key) == null) {   
           cacheMap.put(key,serverbegrundt);   
           return true;   
       }else{   
           return false;   
       }   
   }   
   
   //得到缓存。同步静态方法   
   private synchronized static Cache getCache(String key) {   
       return (Cache) cacheMap.get(key);   
   }   
   
   //判断是否存在一个缓存   
   private synchronized static boolean hasCache(String key) {   
       return cacheMap.containsKey(key);   
   }   
   
   //清除所有缓存   
   public synchronized static void clearAll() {   
       cacheMap.clear();   
   }   
   
   //清除某一类特定缓存,通过遍历HASHMAP下的所有对象,来判断它的KEY与传入的TYPE是否匹配   
   public synchronized static void clearAll(String type) {   
       Iterator i = cacheMap.entrySet().iterator();   
       String key;   
       ArrayList arr = new ArrayList();   
       try {   
           while (i.hasNext()) {   
               java.util.Map.Entry entry = (java.util.Map.Entry) i.next();   
               key = (String) entry.getKey();   
               if (key.startsWith(type)) { //如果匹配则删除掉   
                   arr.add(key);   
               }   
           }   
           for (int k = 0; k < arr.size(); k++) {   
               clearOnly(arr.get(k));   
           }   
       } catch (Exception ex) {   
           ex.printStackTrace();   
       }   
   }   
   
   //清除指定的缓存   
   public synchronized static void clearOnly(String key) {   
       cacheMap.remove(key);   
   }   
   
   //载入缓存   
   public synchronized static void putCache(String key, Cache obj) {   
       cacheMap.put(key, obj);   
   }   
   
   //获取缓存信息   
   public static Cache getCacheInfo(String key) {   
   
       if (hasCache(key)) {   
           Cache cache = getCache(key);   
           if (cacheExpired(cache)) { //调用判断是否终止方法   
               cache.setExpired(true);   
           }   
           return cache;   
       }else 
           return null;   
   }   
   
   //载入缓存信息   
   public static void putCacheInfo(String key, Cache obj, long dt,boolean expired) {   
       Cache cache = new Cache();   
       cache.setKey(key);   
       cache.setTimeOut(dt + System.currentTimeMillis()); //设置多久后更新缓存   
       cache.setValue(obj);   
       cache.setExpired(expired); //缓存默认载入时,终止状态为FALSE   
       cacheMap.put(key, cache);   
   }   
   //重写载入缓存信息方法   
   public static void putCacheInfo(String key,Cache obj,long dt){   
       Cache cache = new Cache();   
       cache.setKey(key);   
       cache.setTimeOut(dt+System.currentTimeMillis());   
       cache.setValue(obj);   
       cache.setExpired(false);   
       cacheMap.put(key,cache);   
   }   
   
   //判断缓存是否终止   
   public static boolean cacheExpired(Cache cache) {   
       if (null == cache) { //传入的缓存不存在   
           return false;   
       }   
       long nowDt = System.currentTimeMillis(); //系统当前的毫秒数   
       long cacheDt = cache.getTimeOut(); //缓存内的过期毫秒数   
       if (cacheDt <= 0||cacheDt>nowDt) { //过期时间小于等于零时,或者过期时间大于当前时间时,则为FALSE   
           return false;   
       } else { //大于过期时间 即过期   
           return true;   
       }   
   }   
   
   //获取缓存中的大小   
   public static int getCacheSize() {   
       return cacheMap.size();   
   }   
   
   //获取指定的类型的大小   
   public static int getCacheSize(String type) {   
       int k = 0;   
       Iterator i = cacheMap.entrySet().iterator();   
       String key;   
       try {   
           while (i.hasNext()) {   
               java.util.Map.Entry entry = (java.util.Map.Entry) i.next();   
               key = (String) entry.getKey();   
               if (key.indexOf(type) != -1) { //如果匹配则删除掉   
                   k++;   
               }   
           }   
       } catch (Exception ex) {   
           ex.printStackTrace();   
       }   
   
       return k;   
   }   
   
   //获取缓存对象中的所有键值名称   
   public static ArrayList getCacheAllkey() {   
       ArrayList a = new ArrayList();   
       try {   
           Iterator i = cacheMap.entrySet().iterator();   
           while (i.hasNext()) {   
               java.util.Map.Entry entry = (java.util.Map.Entry) i.next();   
               a.add((String) entry.getKey());   
           }   
       } catch (Exception ex) {} finally {   
           return a;   
       }   
   }   
   
   //获取缓存对象中指定类型 的键值名称   
   public static ArrayList getCacheListkey(String type) {   
       ArrayList a = new ArrayList();   
       String key;   
       try {   
           Iterator i = cacheMap.entrySet().iterator();   
           while (i.hasNext()) {   
               java.util.Map.Entry entry = (java.util.Map.Entry) i.next();   
               key = (String) entry.getKey();   
               if (key.indexOf(type) != -1) {   
                   a.add(key);   
               }   
           }   
       } catch (Exception ex) {} finally {   
           return a;   
       }   
   }   
   
}   
   
package com.songliguo.cache;   

/**
 * 
 * @ClassName: Cache 
 * @Description: TODO(定义缓存实体对象) 
 * @author SongLiGuo
 * @date 2016-11-3 下午5:02:24 
 *
 */
public class CacheModel {   
       private String key;//缓存ID   
       private Object value;//缓存数据   
       private long timeOut;//更新时间   
       private boolean expired; //是否终止   
       public Cache() {   
               super();   
       }   
   
       public Cache(String key, Object value, long timeOut, boolean expired) {   
               this.key = key;   
               this.value = value;   
               this.timeOut = timeOut;   
               this.expired = expired;   
       }   
   
       public String getKey() {   
               return key;   
       }   
   
       public long getTimeOut() {   
               return timeOut;   
       }   
   
       public Object getValue() {   
               return value;   
       }   
   
       public void setKey(String string) {   
               key = string;   
       }   
   
       public void setTimeOut(long l) {   
               timeOut = l;   
       }   
   
       public void setValue(Object object) {   
               value = object;   
       }   
   
       public boolean isExpired() {   
               return expired;   
       }   
   
       public void setExpired(boolean b) {   
               expired = b;   
       }   
}   
   
/**
 * 
 * @ClassName: TestCache 
 * @Description: TODO(测试缓存操作实现) 
 * @author SongLiGuo
 * @date 2016-11-3 下午5:03:14 
 *
 */
public class TestCache {   
   public static void main(String[] args) {   
       System.out.println(CacheManager.getSimpleFlag("alksd"));   
//       CacheManager.putCache("abc", new Cache());   
//       CacheManager.putCache("def", new Cache());   
//       CacheManager.putCache("ccc", new Cache());   
//       CacheManager.clearOnly("");   
//       Cache c = new Cache();   
//       for (int i = 0; i < 10; i++) {   
//           CacheManager.putCache("" + i, c);   
//       }   
//       CacheManager.putCache("aaaaaaaa", c);   
//       CacheManager.putCache("abchcy;alskd", c);   
//       CacheManager.putCache("cccccccc", c);   
//       CacheManager.putCache("abcoqiwhcy", c);   
//       System.out.println("删除前的大小:"+CacheManager.getCacheSize());   
//       CacheManager.getCacheAllkey();   
//       CacheManager.clearAll("aaaa");   
//       System.out.println("删除后的大小:"+CacheManager.getCacheSize());   
//       CacheManager.getCacheAllkey();   
   
   }   
}
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China.BeiJing

如果说人生是自我编写的程序,那么青春就是其中意味深长的代码