缓存构建基于Redis的Java过期缓存系统（redisjava过期）
Cache building Java-based expiration caching system based on Redis
Caching is a widely adopted technique to improve the performance of applications and online services. It is used to store data in memory so that future requests can be served faster. Caching also helps in reducing load times, network resources and improving scalability.
The goal of this article is to discuss the build of a Java-based caching system based on Redis, a popular open source data structure store for caching. Redis provides great flexibility for storing and retrieving data and can be configured for expiration which makes it a great choice for caching system.
Redis stores data as key-value pairs. In the example shown below, we will use a HashMap type to store the data. The key is the cache key, and the value is an object containing the actual data and an expiration time.
HashMap cache = new HashMap();
The CacheObject class will store the actual data and the expiration time.
public class CacheObject {
private Object data;
private long expirationTime;
public CacheObject(Object data, long expirationTime) {
this.data = data;
this.expirationTime = expirationTime;
}
public Object getData() {
return data;
}
public void setData(Object data) {
this.data = data;
}
public long getExpirationTime() {
return expirationTime;
}
public void setExpirationTime(long expirationTime) {
this.expirationTime = expirationTime;
}
}
Now, we will use the Redis client library to connect to the Redis server from our Java application. Once connected, we will use the Redis commands to store the HashMap containing the cached values.
Jedis jedis = new Jedis(“localhost”);
for(Map.Entry entry : cache.entrySet()) {
jedis.hset(entry.getKey(), entry.getValue().toString());
}
We can set the expiration time for each value stored in Redis by using the expire() command. This will allow us to control the lifetime of each piece of cached data.
for(Map.Entry entry : cache.entrySet()) {
jedis.expire(entry.getKey(), entry.getValue().getExpirationTime());
}
Finally, we can implement a simple eviction policy to remove expired entries from the cache. We can use the Redis TTL command to get the remaining time for each entry in the cache. If the time is less than 0, then the entry needs to be evicted.
for(Map.Entry entry : cache.entrySet()) {
long currentTime = System.currentTimeMillis();
long ttl = jedis.ttl(entry.getKey());
if (ttl
jedis.del(entry.getKey());
}
}
This article has discussed how to build a Java-based expiration caching system using Redis. The provided example code should give enough of an idea how to use Redis for caching. It is recommended to implement the eviction policy discussed in this article as well as other caching strategies based on the application’s needs.
