自定义Map实现K,V过期时间检测

项目中遇到一个需求，前台每秒请求一次后台，得到json数据展示到页面，json中需要一个state值，如果state=1，则代表正常在线状态，state=2，代表报警状态，并且此报警状态需要持续十秒，十秒后状态变正常。此时需要在全局维护一个带过期时间（10s）的Map。

import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
 

public class ExpiryMap<K, V> extends HashMap<K, V>{
 
    private static final long serialVersionUID = 1L;
    
    /**
     * default expiry time 2m
     */
    private long EXPIRY = 1000 * 60 * 2;
    
    private HashMap<K, Long> expiryMap = new HashMap<>();
    
    public ExpiryMap(){
        super();
    }
    public ExpiryMap(long defaultExpiryTime){
        this(1 << 4, defaultExpiryTime);
    }
    public ExpiryMap(int initialCapacity, long defaultExpiryTime){
        super(initialCapacity);
        this.EXPIRY = defaultExpiryTime;
    }
    public V put(K key, V value) {
        expiryMap.put(key, System.currentTimeMillis() + EXPIRY);
        return super.put(key, value);
    }
     public boolean containsKey(Object key) {
         return !checkExpiry(key, true) && super.containsKey(key);
     }
    /**
         * @param key
         * @param value
         * @param expiryTime 键值对有效期 毫秒
         * @return
     */
    public V put(K key, V value, long expiryTime) {
        expiryMap.put(key, System.currentTimeMillis() + expiryTime);
        return super.put(key, value);
    }
    public int size() {
        return entrySet().size();
    }
    public boolean isEmpty() {
        return entrySet().size() == 0;
    }
    public boolean containsValue(Object value) {
        if (value == null) return Boolean.FALSE;
        Set<java.util.Map.Entry<K, V>> set = super.entrySet();
        Iterator<java.util.Map.Entry<K, V>> iterator = set.iterator();
        while (iterator.hasNext()) {
            java.util.Map.Entry<K, V> entry = iterator.next();
            if(value.equals(entry.getValue())){
                if(checkExpiry(entry.getKey(), false)) {
                    iterator.remove();
                    return Boolean.FALSE;
                }else return Boolean.TRUE;
            }
        }
        return Boolean.FALSE;
    }
    public Collection<V> values() {
        
        Collection<V> values = super.values();
        
        if(values == null || values.size() < 1) return values;
        
        Iterator<V> iterator = values.iterator();
        
        while (iterator.hasNext()) {
            V next = iterator.next();
            if(!containsValue(next)) iterator.remove();
        }
        return values;
    }
    public V get(Object key) {
        if (key == null)
            return null;
        if(checkExpiry(key, true))
            return null;
        return super.get(key);
    }
    /**
     * 
         * @Description: 是否过期 
         * @param key
         * @return null:不存在或key为null -1:过期  存在且没过期返回value 因为过期的不是实时删除，所以稍微有点作用
     */
    public Object isInvalid(Object key) {
        if (key == null)
            return null;
        if(!expiryMap.containsKey(key)){
            return null;
        }
        long expiryTime = expiryMap.get(key);
        
        boolean flag = System.currentTimeMillis() > expiryTime;
        
        if(flag){
            super.remove(key);
            expiryMap.remove(key);
            return -1;
        }
        return super.get(key);
    }
    public void putAll(Map<? extends K, ? extends V> m) {
         for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
                expiryMap.put(e.getKey(), System.currentTimeMillis() + EXPIRY);
         super.putAll(m);
    }
    public Set<Map.Entry<K,V>> entrySet() {
        Set<java.util.Map.Entry<K, V>> set = super.entrySet();
        Iterator<java.util.Map.Entry<K, V>> iterator = set.iterator();
        while (iterator.hasNext()) {
            java.util.Map.Entry<K, V> entry = iterator.next();
            if(checkExpiry(entry.getKey(), false)) iterator.remove();
        }
        
        return set;
    }
    /**
     * 
         * @Description: 是否过期 
         * @author: qd-ankang
         * @date: 2016-11-24 下午4:05:02
         * @param expiryTime true 过期
         * @param isRemoveSuper true super删除
         * @return
     */
    private boolean checkExpiry(Object key, boolean isRemoveSuper){
        
        if(!expiryMap.containsKey(key)){
            return Boolean.FALSE;
        }
        long expiryTime = expiryMap.get(key);
        
        boolean flag = System.currentTimeMillis() > expiryTime;
        
        if(flag){
            if(isRemoveSuper)
                super.remove(key);
            expiryMap.remove(key);
        }
        return flag;
    }
}