如题，直接上代码：
1 import java.util.Iterator;
2 import java.util.concurrent.ConcurrentHashMap;
3 import java.util.concurrent.TimeUnit;
4
5 import org.slf4j.Logger;
6 import org.slf4j.LoggerFactory;
7
8 /**
9 * 实现延时过期MAP集合 支持自定义过期触发事件
10 *
11 * @ClassName: BaseExpireMap
12 * @Description: TODO
13 * @author: wangs
14 * @date: 2017-12-25 上午9:59:04
15 * @param <K>
16 * @param <V>
17 */
18 public abstract class BaseExpireMap<K, V> {
19 protected static final Logger logger = LoggerFactory.getLogger(BaseExpireMap.class);
20 private long expTime = 0L;
21 private TimeUnit unit = null;
22 /**
23 * 线程安全的map容器
24 */
25 ConcurrentHashMap<K, V> expireMap = null;
26 /**
27 * 控制过期时间
28 */
29 ConcurrentHashMap<K, Long> delayMap = null;
30
31 /**
32 * 将map提供给外部程序操作
33 * @Title: getDataMap
34 * @Description: TODO
35 * @return
36 * @return: ConcurrentHashMap<K,V>
37 */
38 public ConcurrentHashMap<K, V> getDataMap(){
39 return this.expireMap;
40 }
41
42 public BaseExpireMap(long expTime, TimeUnit unit) {
43 expireMap = new ConcurrentHashMap<K, V>();
44 delayMap = new ConcurrentHashMap<K, Long>();
45 this.expTime = expTime;
46 this.unit = unit;
47 // 启动监听线程
48 BaseExpireCheckTask task = new BaseExpireCheckTask(expireMap, delayMap) {
49 @Override
50 protected void expireEvent(K key,V val) {
51 baseExpireEvent(key,val);
52 }
53 };
54 task.setDaemon(false);
55 task.start();
56 }
57
58 /**
59 * 过期事件 子类实现
60 *
61 * @Title: baseExpireEvent
62 * @Description: TODO
63 * @param key
64 * @return: void
65 */
66 protected abstract void baseExpireEvent(K key,V val);
67
68 public V put(K key, V val) {
69 delayMap.put(key, getExpireTime());
70 return expireMap.put(key, val);
71 }
72
73 public V remove(K key) {
74 return expireMap.remove(key);
75 }
76
77 public V get(K key){
78 return expireMap.get(key);
79 }
80
81 private Long getExpireTime() {
82 return unit.toMillis(expTime) + System.currentTimeMillis();
83 }
84
85 public static void main(String[] args) {
86 System.out.println(TimeUnit.SECONDS.toMinutes(120));
87 System.out.println(TimeUnit.MICROSECONDS.toMillis(120));
88 System.out.println(TimeUnit.MILLISECONDS.toMillis(120));
89 }
90
91 /**
92 * 扫描线程 定期移除过期元素并触发过期事件
93 *
94 * @ClassName: BaseExpireCheckTask
95 * @Description: TODO
96 * @author: wangs
97 * @date: 2017-12-25 上午9:59:18
98 */
99 private abstract class BaseExpireCheckTask extends Thread {
100 ConcurrentHashMap<K, Long> delayMap = null;
101 ConcurrentHashMap<K, V> expireMap = null;
102
103 public BaseExpireCheckTask(ConcurrentHashMap<K, V> expireMap, ConcurrentHashMap<K, Long> delayMap) {
104 this.delayMap = delayMap;
105 this.expireMap = expireMap;
106 }
107
108 protected abstract void expireEvent(K key,V val);
109
110 public void run() {
111 Iterator<K> it = null;
112 K key = null;
113 while (true) {
114 if (delayMap != null && !delayMap.isEmpty()) {
115 it = delayMap.keySet().iterator();
116 while (it.hasNext()) {
117 key = it.next();
118 if (delayMap.get(key) <= System.currentTimeMillis()) {// 元素超时
119 // 触发回调
120 expireEvent(key,expireMap.get(key));
121 // 移除
122 it.remove();
123 expireMap.remove(key);
124 delayMap.remove(key);
125 }
126 }
127 }
128 try {
129 TimeUnit.MILLISECONDS.sleep(200);
130 } catch (InterruptedException e) {
131 logger.error(e.getMessage());
132 }
133 }
134 }
135 }
136 }上面是一个通用的延迟过期MAP容器，由两个线程安全的map集合和一个扫描线程组成，该容器会定时移除超时的元素并在移除时触发指定事件expireEvent，该方法的两个参数Key和val分别代表过期元素的键值，定义了元素过期时的触发事件，等待子类实现。
下面是一个使用实例：
1 import java.util.concurrent.TimeUnit;
2
3 import com.montnets.kafka.Producer;
4 import com.montnets.smsverify.bean.VerifyAccountSeatBean;
5 import com.montnets.smsverify.common.StaticValues;
6 import com.montnets.smsverify.netty.utils.GsonUtil;
7
8 /**
9 * 进退坐席缓存
10 *
11 * @ClassName: SeatCache
12 * @Description: 单例
13 * @author: wangs
14 * @date: 2017-12-25 下午2:23:21
15 */
16 public class SeatCache extends BaseExpireMap<String, VerifyAccountSeatBean> {
17 private static SeatCache instance = null;
18 private static Producer producer = null;
19 static long expTime = 0L;
20 static TimeUnit unit = null;
21
22 private SeatCache(long expTime, TimeUnit unit) {
23 super(expTime, unit);
24 }
25
26 public synchronized static void init(long expTime, TimeUnit unit) {
27 SeatCache.expTime = expTime;
28 SeatCache.unit = unit;
29 if (instance == null) {
30 instance = new SeatCache(expTime, unit);
31 producer = new Producer();
32 }
33 }
34
35 public synchronized static SeatCache getInstance() {
36 if (instance == null) {
37 if (unit == null)
38 throw (new IllegalArgumentException("please call init at first"));
39 instance = new SeatCache(expTime, unit);
40 producer = new Producer();
41 }
42 return instance;
43 }
44
45
46 /**
47 * 过期事件
48 */
49 @Override
50 protected void baseExpireEvent(String key, VerifyAccountSeatBean bean) {
51 if(bean!=null)
52 bean.setIsManual(1); //非手动退坐席
53 //更新
54 updateOffOnlie(bean);
55 //写kafka
56 send2kafka(bean);
57 }
58
59 /**
60 * 退坐席之前更新时间标记
61 * @Title: updateOffOnlie
62 * @Description: TODO
63 * @param bean
64 * @return: void
65 */
66 public static void updateOffOnlie(VerifyAccountSeatBean bean) {
67 if (bean != null) {
68 long now = System.currentTimeMillis();
69 // 退坐席时间
70 bean.setOutSeatTime(now);
71 // 在线时长
72 bean.setOnlineTime(now - bean.getInSeatTime());
73 }
74 }
75
76 /**
77 * 退坐席时将数据写入kafka
78 *
79 * @Title: send2kafka
80 * @Description: TODO
81 * @param topic
82 * @param bean
83 * @return: void
84 */
85 public static void send2kafka(VerifyAccountSeatBean bean) {
86 if (bean == null)
87 return;
88 producer.send(StaticValues.SEAT_DATA, GsonUtil.toJson(bean));
89 }
90 }推荐一个很强大的过期缓存第三方工具包，com.google.common.cache.Cache ，它提供多种回收策略，如基于创建时间或最后一次访问时间计时回收、基于对象容量大小回收、按照命中率使用LRU算法回收等，并且一样可以自定义过期回收触发事件（写这个工具的时候我还不知道有这么个强大的玩意 - -）；另外还提供命中统计的API，功能很全，可以用作数据库到前端页面中间的缓存模块，推荐使用。
世间之事莫强求，凡事太尽，缘分势必早尽。
来源：oschina
链接：https://my.oschina.net/u/4385489/blog/4034173