java 本地缓存

public class LocalCache {

    private static ConcurrentHashMap<String, LocalCacheItem> map = new ConcurrentHashMap<String, LocalCacheItem>();

    public static boolean containsKey(String key){
        return map.containsKey(key);
    }
    
    public static void put(String key, Object value){
        put(key, value, 0);//0值代表永不过期
    }
    
    public static void put(String key, Object value, long expireTimeMillis){
        LocalCacheItem item = new LocalCacheItem(value, System.currentTimeMillis(), expireTimeMillis);
        map.put(key, item);
    }
    
    public static Object get(String key) {
        return key == null ? null : getValue(key);
    }
    
    private static Object getValue(String key) {
        LocalCacheItem item = map.get(key);
        
        if (item == null) return null;
        
        long currentTime = System.currentTimeMillis();
        if (item.getExpireTimeMillis() > 0 && item.getExpireTimeMillis() < currentTime - item.getCreateTimeMillis()) {
            map.remove(key);
            return null;
        }
        
        return item.getValue();    
    }
    
    static class LocalCacheItem {
        
        /**
         * 缓存对象
         */
        private Object value;
        
        /**
         * 缓存创建时间
         */
        private long createTimeMillis;        
        
        /**
         * 缓存过期时间，0值代表永不过期
         */
        private long expireTimeMillis;

        public LocalCacheItem(Object value, long createTimeMillis, long expireTimeMillis) {
            this.value = value;
            this.createTimeMillis = createTimeMillis;
            this.expireTimeMillis = expireTimeMillis;
        }
        
        public Object getValue() {
            return value;
        }

        public void setValue(Object value) {
            this.value = value;
        }

        public long getCreateTimeMillis() {
            return createTimeMillis;
        }

        public void setCreateTimeMillis(long createTimeMillis) {
            this.createTimeMillis = createTimeMillis;
        }

        public long getExpireTimeMillis() {
            return expireTimeMillis;
        }

        public void setExpireTimeMillis(long expireTimeMillis) {
            this.expireTimeMillis = expireTimeMillis;
        }

    }
}

@Override
    public WechatConfigInfo getWechatConfigInfoByAppCode(Integer appCode) {
        String localCacheKey = WechatConstant.LOCAL_CACHE_WECHAT_CONFIG + appCode;
        WechatConfigInfo cfg = (WechatConfigInfo)LocalCache.get(localCacheKey);
        
        if (cfg != null)) {
            return cfg;
        }
        if (checkValid) {            
            cfg = wechatConfigInfoMapper.getWechatConfigInfoByAppCode(appCode);
            LocalCache.put(localCacheKey, cfg, defaultExpireTimeMinutes*60*1000);
            return cfg;
        }
        
        cfg = wechatConfigInfoMapper.getWechatConfigInfoByAppCode(appCode);
        LocalCache.put(localCacheKey, cfg, defaultExpireTimeMinutes*60*1000);
        return cfg;
    }