首先要了解下java1.6中的ConcurrentMap ,他是一个线程安全的Map实现,特别说明的是在没有特别需求的情况下可以用ConcurrentHashMap。我是想学习一下读写锁的应用,就自己实现了一个SimpleConcurrentHashMap.
- package com.cttc.cache.entity;
- import java.util.ArrayList;
- import java.util.Collection;
- import java.util.HashSet;
- import java.util.Map;
- import java.util.Set;
- import java.util.concurrent.locks.Lock;
- import java.util.concurrent.locks.ReadWriteLock;
- import java.util.concurrent.locks.ReentrantReadWriteLock;
- public class SimpleConcurrentMap<K, V> implements Map<K, V> {
- final ReadWriteLock lock = new ReentrantReadWriteLock();
- final Lock r = lock.readLock();
- final Lock w = lock.writeLock();
- final Map<K, V> map;
- public SimpleConcurrentMap(Map<K, V> map) {
- this.map = map;
- if (map == null) throw new NullPointerException();
- }
- public void clear() {
- w.lock();
- try {
- map.clear();
- } finally {
- w.unlock();
- }
- }
- public boolean containsKey(Object key) {
- r.lock();
- try {
- return map.containsKey(key);
- } finally {
- r.unlock();
- }
- }
- public boolean containsValue(Object value) {
- r.lock();
- try {
- return map.containsValue(value);
- } finally {
- r.unlock();
- }
- }
- public Set<java.util.Map.Entry<K, V>> entrySet() {
- throw new UnsupportedOperationException();
- }
- public V get(Object key) {
- r.lock();
- try {
- return map.get(key);
- } finally {
- r.unlock();
- }
- }
- public boolean isEmpty() {
- r.lock();
- try {
- return map.isEmpty();
- } finally {
- r.unlock();
- }
- }
- public Set<K> keySet() {
- r.lock();
- try {
- return new HashSet<K>(map.keySet());
- } finally {
- r.unlock();
- }
- }
- public V put(K key, V value) {
- w.lock();
- try {
- return map.put(key, value);
- } finally {
- w.unlock();
- }
- }
- public void putAll(Map<? extends K, ? extends V> m) {
- w.lock();
- try {
- map.putAll(m);
- } finally {
- w.unlock();
- }
- }
- public V remove(Object key) {
- w.lock();
- try {
- return map.remove(key);
- } finally {
- w.unlock();
- }
- }
- public int size() {
- r.lock();
- try {
- return map.size();
- } finally {
- r.unlock();
- }
- }
- public Collection<V> values() {
- r.lock();
- try {
- return new ArrayList<V>(map.values());
- } finally {
- r.unlock();
- }
- }
- }
缓存对象CacheEntity.java为:
- package com.cttc.cache.entity;
- import java.io.Serializable;
- public class CacheEntity implements Serializable{
- private static final long serialVersionUID = -3971709196436977492L;
- private final int DEFUALT_VALIDITY_TIME = 20;//默认过期时间 20秒
- private String cacheKey;
- private Object cacheContext;
- private int validityTime;//有效期时长,单位:秒
- private long timeoutStamp;//过期时间戳
- private CacheEntity(){
- this.timeoutStamp = System.currentTimeMillis() + DEFUALT_VALIDITY_TIME * 1000;
- this.validityTime = DEFUALT_VALIDITY_TIME;
- }
- public CacheEntity(String cacheKey, Object cacheContext){
- this();
- this.cacheKey = cacheKey;
- this.cacheContext = cacheContext;
- }
- public CacheEntity(String cacheKey, Object cacheContext, long timeoutStamp){
- this(cacheKey, cacheContext);
- this.timeoutStamp = timeoutStamp;
- }
- public CacheEntity(String cacheKey, Object cacheContext, int validityTime){
- this(cacheKey, cacheContext);
- this.validityTime = validityTime;
- this.timeoutStamp = System.currentTimeMillis() + validityTime * 1000;
- }
- public String getCacheKey() {
- return cacheKey;
- }
- public void setCacheKey(String cacheKey) {
- this.cacheKey = cacheKey;
- }
- public Object getCacheContext() {
- return cacheContext;
- }
- public void setCacheContext(Object cacheContext) {
- this.cacheContext = cacheContext;
- }
- public long getTimeoutStamp() {
- return timeoutStamp;
- }
- public void setTimeoutStamp(long timeoutStamp) {
- this.timeoutStamp = timeoutStamp;
- }
- public int getValidityTime() {
- return validityTime;
- }
- public void setValidityTime(int validityTime) {
- this.validityTime = validityTime;
- }
- }
List缓存处理对象:
[java] view plaincopyprint?
- package com.cttc.cache.handler;
- import java.util.ArrayList;
- import java.util.HashMap;
- import java.util.List;
- import com.cttc.cache.entity.CacheEntity;
- import com.cttc.cache.entity.SimpleConcurrentMap;
- public class CacheListHandler {
- private static final long SECOND_TIME = 1000;
- private static final SimpleConcurrentMap<String, CacheEntity> map;
- private static final List<CacheEntity> tempList;
- static{
- tempList = new ArrayList<CacheEntity>();
- map = new SimpleConcurrentMap<String, CacheEntity>(new HashMap<String, CacheEntity>(1<<18));
- new Thread(new TimeoutTimerThread()).start();
- }
- /**
- * 增加缓存对象
- * @param key
- * @param ce
- */
- public static void addCache(String key, CacheEntity ce){
- addCache(key, ce, ce.getValidityTime());
- }
- /**
- * 增加缓存对象
- * @param key
- * @param ce
- * @param validityTime 有效时间
- */
- public static synchronized void addCache(String key, CacheEntity ce, int validityTime){
- ce.setTimeoutStamp(System.currentTimeMillis() + validityTime * SECOND_TIME);
- map.put(key, ce);
- //添加到过期处理队列
- tempList.add(ce);
- }
- /**
- * 获取缓存对象
- * @param key
- * @return
- */
- public static synchronized CacheEntity getCache(String key){
- return map.get(key);
- }
- /**
- * 检查是否含有制定key的缓冲
- * @param key
- * @return
- */
- public static synchronized boolean isConcurrent(String key){
- return map.containsKey(key);
- }
- /**
- * 删除缓存
- * @param key
- */
- public static synchronized void removeCache(String key){
- map.remove(key);
- }
- /**
- * 获取缓存大小
- * @param key
- */
- public static int getCacheSize(){
- return map.size();
- }
- /**
- * 清除全部缓存
- */
- public static synchronized void clearCache(){
- tempList.clear();
- map.clear();
- System.out.println("clear cache");
- }
- static class TimeoutTimerThread implements Runnable {
- public void run(){
- while(true){
- try {
- checkTime();
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- }
- /**
- * 过期缓存的具体处理方法
- * @throws Exception
- */
- private void checkTime() throws Exception{
- //"开始处理过期 ";
- CacheEntity tce = null;
- long timoutTime = 1000L;
- //" 过期队列大小 : "+tempList.size());
- if(1 > tempList.size()){
- System.out.println("过期队列空,开始轮询");
- timoutTime = 1000L;
- Thread.sleep(timoutTime);
- return;
- }
- tce = tempList.get(0);
- timoutTime = tce.getTimeoutStamp() - System.currentTimeMillis();
- //" 过期时间 : "+timoutTime);
- if(0 < timoutTime){
- //设定过期时间
- Thread.sleep(timoutTime);
- return;
- }
- System.out.print(" 清除过期缓存 : "+tce.getCacheKey());
- //清除过期缓存和删除对应的缓存队列
- tempList.remove(tce);
- removeCache(tce.getCacheKey());
- }
- }
- }
时间: 2024-08-05 23:47:54