Java中常用缓存Cache机制的实现

import java.util.*; 

 //Description: 管理缓存 

 //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 

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 lhm.hcy.guge.frameset.cache; 

public class Cache { 
  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; 
  } 
} 

//测试类， 
class Test { 
 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(); 


 } 
}