Java缓存及过期处理的简单实现「建议收藏」

全栈程序员站长

发布于 2022-11-09 14:42:15

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大家好，又见面了，我是你们的朋友全栈君。

1. 创建缓存实体类

保存需要缓存的数据，缓存创建的时间和缓存的有效期

/** * 缓存类实体类 */
public class CacheEntity<T> { 

/** * 要存储的数据 */
private T value;
/** * 创建的时间 单位ms */
private long createTime = System.currentTimeMillis();
/** * 缓存的有效时间 单位ms （小于等于0表示永久保存） */
private long cacheTime;
public CacheEntity() { 

super();
}
public CacheEntity(T value, long cacheTime) { 

this.value = value;
this.cacheTime = cacheTime;
}
public T getValue() { 

return value;
}
public void setValue(T value) { 

this.value = value;
}
public long getCreateTime() { 

return createTime;
}
public void setCreateTime(long createTime) { 

this.createTime = createTime;
}
public long getCacheTime() { 

return cacheTime;
}
public void setCacheTime(long cacheTime) { 

this.cacheTime = cacheTime;
}
}

2. 缓存的管理类

主要用户管理缓存数据，对数据的添加，删除。对缓存数据有效性校验，其中创建了一个Timer定时任务，每分钟执行一次缓存清理。

import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;
/** * 缓存管理器 */
public class CacheManager { 

/** * 缓存Map对象 */
private static ConcurrentHashMap<String,CacheEntity> cacheMap = new ConcurrentHashMap<>();
/** * 创建定时任务每分钟清理一次缓存 */
static{ 

Timer timer = new Timer();
timer.schedule(new TimerTask() { 

@Override
public void run() { 

refresh();
}
},0,60000);
}
/** * 缓存刷新,清除过期数据 */
public static void refresh(){ 

for (String key : cacheMap.keySet()) { 

if(isExpire(key)){ 

remove(key);
}
}
}
/** * 加入缓存 * @param key * @param value */
public static boolean put(String key,Object value){ 

if(key.isEmpty()){ 

return false;
}
CacheEntity<Object> cacheEntity = new CacheEntity<>();
cacheEntity.setCacheTime(0);
cacheEntity.setValue(value);
cacheMap.put(key,cacheEntity);
return true;
}
/** * 加入缓存，包含过期时间 * @param key 缓存数据的关键字 * @param value 缓存数据 * @param cacheTime 要缓存的时间 * @param timeUnit 时间单位 */
public static boolean put(String key, Object value,long cacheTime,TimeUnit timeUnit){ 

if(key.isEmpty()){ 

return false;
}
CacheEntity<Object> cacheEntity = new CacheEntity<>();
cacheEntity.setCacheTime(timeUnit.toMillis(cacheTime));
cacheEntity.setValue(value);
cacheMap.put(key,cacheEntity);
return true;
}
/** * 移除缓存数据 * @param key */
public static boolean remove(String key){ 

if(key.isEmpty()){ 

return false;
}
if(!cacheMap.containsKey(key)){ 

return true;
}
cacheMap.remove(key);
return true;
}
/** * 获取缓存数据 * @param key * @return */
public static Object get(String key){ 

if(key.isEmpty()||isExpire(key)){ 

return null;
}
CacheEntity cacheEntity = cacheMap.get(key);
if(null == cacheEntity){ 

return null;
}
return cacheEntity.getValue();
}
/** * 判断当前数据是否已过期 * @param key * @return */
private static boolean isExpire(String key){ 

if(key.isEmpty()){ 

return false;
}
if(cacheMap.containsKey(key)){ 

CacheEntity cacheEntity = cacheMap.get(key);
long createTime = cacheEntity.getCreateTime();
long currentTime = System.currentTimeMillis();
long cacheTime = cacheEntity.getCacheTime();
if(cacheTime>0&&currentTime-createTime>cacheTime){ 

return true;
}
return false;
}
return false;
}
/** * 获取当前缓存大小（包含已过期但未清理的数据） * @return */
public static int getCacheSize(){ 

return cacheMap.size();
}
}

3. 缓存的测试类

验证缓存对数据的存储，提取及对数据有效性的验证。

import java.util.concurrent.TimeUnit;
/** * 测试类 */
public class Main { 

public static void main(String[] args) throws InterruptedException { 

// try { 

// Class.forName(CacheManager.class.getName());
// } catch (ClassNotFoundException e) { 

// e.printStackTrace();
// }
CacheManager.put("one","第一个数据");
CacheManager.put("two","第二条数据",50, TimeUnit.SECONDS);
CacheManager.put("three","第三条数据",3,TimeUnit.MINUTES);
System.out.println("立刻获取------------------------");
System.out.println(CacheManager.get("one"));
System.out.println(CacheManager.get("two"));
System.out.println(CacheManager.get("three"));
Thread.sleep(55000);
System.out.println("55秒后------------------------");
System.out.println(CacheManager.get("one"));
System.out.println(CacheManager.get("two"));
System.out.println(CacheManager.get("three"));
Thread.sleep(60000-55000);
System.out.println("1分钟后------------------------");
System.out.println(CacheManager.get("one"));
System.out.println(CacheManager.get("two"));
System.out.println(CacheManager.get("three"));
Thread.sleep(120000-60000);
System.out.println("2分钟后------------------------");
System.out.println(CacheManager.get("one"));
System.out.println(CacheManager.get("two"));
System.out.println(CacheManager.get("three"));
Thread.sleep(180000-120000);
System.out.println("3分钟时------------------------");
System.out.println(CacheManager.get("one"));
System.out.println(CacheManager.get("two"));
System.out.println(CacheManager.get("three"));
Thread.sleep(190000-180000);
System.out.println("3分钟10秒后------------------------");
System.out.println(CacheManager.get("one"));
System.out.println(CacheManager.get("two"));
System.out.println(CacheManager.get("three"));
System.out.println("缓存的大小: "+CacheManager.getCacheSize());
System.out.println("main over------------------------");
}
}