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VA缓存的实现

 2009-12-18 21:12:24 来源:WEB开发网   
核心提示:package lhm.hcy.guge.frameset.cache;import java.util.*;/** * <p>Title: </p> * * <p>Description: 管理缓存</p> * Deep blue 2008-11-28 think *
package lhm.hcy.guge.frameset.cache;

import java.util.*;

/**
* <p>Title: </p>
*
* <p>Description: 管理缓存</p>
* Deep blue 2008-11-28 think
* 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
* <p>Copyright: Copyright (c) 2008</p>
*
* <p>Company: </p>
*
* @author Deepblue 2008-11-11
* @version 1.0
*/
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<String> arr = new ArrayList<String>();
    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<String> 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<String> 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;

/**
* <p>Title: </p>
*
* <p>Description: 缓存DTO</p>
*
* <p>Copyright: Copyright (c) 2008</p>
*
* <p>Company: </p>
*
* @author Deepblue 2008-11-11
* @version 1.0
*/
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();


  }
}



本文来自CSDN博客,转载请标明出处:http://blog.csdn.net/hello_zhenyu/archive/2009/12/18/5030366.aspx

Tags:VA 缓存 实现

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