机制RedisJava实现的过期机制（redisjava过期）
With the development of technology today, many companies are becoming more and more dependent on service platforms. Among them, Redis is one of the most commonly used components. Redis is used as a distributed cache, which stores data structure remotely. In many cases, expire mechanism is very important in Redis. Therefore, this article will focus on how to implement expire mechanism in Redis with Java.
First of all, let’s take a look at the theoretical situation. Redis provides a number of commands that can be used to manipulate different data structures. The SETEX command is one of the useful commands for expire mechanism. This command accepts three parameters: a key, an expiration time (given in seconds) and the value being set. When the expiration time is reached, a special expiration event is triggered. This event can be used to expire the key.
The practical scenario is a bit different. In order for the expire mechanism to work, the client needs to set and monitor a timer for each key specified in the SETEX command. Whenever the timer is up, the client will check the key, and if it is expired, remove it from the cache and notify the client.
Now let’s take a look at the Java code. First, we need to create a Timer class to manage and monitor the timer. This timer class should contain a “start” method, which will start the timer, and a “stop” method, which will stop the timer and remove the corresponding key from the cache.
public class ExpireTimer {
private String key;
private Timer timer;
private Long expirationTime;
public ExpireTimer(String key, Long expirationTime){
this.key = key;
this.expirationTime = expirationTime * 1000; //convert to millisecond
timer = new Timer(true); // Create a daemon thread
}
public void start(){
timer.schedule(new TimerTask(){
@Override
public void run(){
Long currentTime = System.currentTimeMillis();
if(currentTime > expirationTime){
RedisUtil.del(key);
timer.cancel();
}
}
},0,1000);
}
public void stop(){
timer.cancel();
RedisUtil.del(key);
}
}
Then we need to define RedisUtil class to manage redis operations. This class contains various utility methods, such as set, get, del etc.
public class RedisUtil {
JedisPool jedisPool;
//constructor method put here
public static void set(String key, String value, Long expireTime){
try(Jedis jedis = jedisPool.getResource()){
jedis.set(key, value);
jedis.expire(key, expireTime.intValue());
}
}
public static void get(String key){
try(Jedis jedis = jedisPool.getResource()){
return jedis.get(key);
}
}
public static void del(String key){
try(Jedis jedis = jedisPool.getResource()){
jedis.del(key);
}
}
}
Finally,we can call these public methods to set,get and delete keys in Redis with expire time.
public static void main(String[] args){
String key = “mykey”;
String value = “myvalue”;
Long expireTime = 10L;
//set the key with expiration time
RedisUtil.set(key, value, expireTime);
//get the key
String result = RedisUtil.get(key);
System.out.println(“result: ” + result);
//create a timer to monitor and delete the key when expiration time is reached
ExpireTimer expireTimer = new ExpireTimer(key, expireTime);
expireTimer.start();
//wait 15 second
Thread.sleep(15000);
//stop the timer and delete the key from cache
expireTimer.stop();
}
To sum up, expire mechanism is a very important feature of Redis and it can be used to obey the principle of least privilege and prevent stale data. Using Java to implement this mechanism is a relatively easy task, but it needs to pay attention to performance and consider potential errors. After all, Redis needs to provide reliable and high-performance services to its users.
