在
開發
項目工程時,經常會遇到保存某些值放
到系統的
cache
中,現用
Cache.java
和
CacheManager.java
來管理。具體
代碼
分別如下:
public class Cache {
private String key;
private Object value;
private long timeOut;
private boolean expired;
public Cache() {
super();
}
public Cache(String key, String
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;
}
}
另
外一個類:
import
java
.util.Date;
import java.util.HashMap;
public class CacheManager {
private static HashMap cacheMap =
new HashMap();
/**
* This class is singleton so
private constructor is used.
*/
private CacheManager() {
super();
}
/**
* returns cache item from
hashmap
* @param key
* @return Cache
*/
private synchronized static Cache
getCache(String key) {
return (Cache)cacheMap.get(key);
}
/**
* Looks at
the
hashmap
if a cache item exists or
not
* @param key
* @return Cache
*/
private synchronized static boolean
hasCache(String key) {
return cacheMap.containsKey(key);
}
/**
* Invalidates all cache
*/
public synchronized static void
invalidateAll() {
cacheMap.clear();
}
/**
* Invalidates a single cache
item
* @param key
*/
public synchronized static void
invalidate(String key) {
cacheMap.remove(key);
}
/**
* Adds new item to cache
hashmap
* @param key
* @return Cache
*/
private synchronized static void
putCache(String key, Cache object) {
cacheMap.put(key,
object);
}
/**
* Reads a cache item's content
* @param key
* @return
*/
public static Cache
getContent(String key) {
if (hasCache(key)) {
Cache cache = getCache(key);
if (cacheExpired(cache)) {
cache.setExpired(true);
}
return cache;
} else {
return null;
}
}
/**
*
* @param key
* @param content
* @param ttl
*/
public static void putContent(String
key, Object content, long ttl) {
Cache cache = new Cache();
cache.setKey(key);
cache.setValue(content);
cache.setTimeOut(ttl + new Date().getTime());
cache.setExpired(false);
putCache(key, cache);
}
/** @modelguid {172828D6-3AB2-46C4-96E2-E72B34264031} */
private static boolean
cacheExpired(Cache cache) {
if (cache == null) {
return false;
}
long milisNow = new Date().getTime();
long milisExpire = cache.getTimeOut();
if (milisExpire < 0)
{
// Cache never expires
return false;
} else if (milisNow >= milisExpire) {
return true;
} else {
return false;
}
}
}