Cache condition deletion in Java caching technology

As the scale of business data in various applications becomes larger and larger, caching technology has become an important means of optimizing the performance of many applications. Cache conditional deletion in Java caching technology is a very important mechanism that allows applications to automatically delete some expired or useless data from the cache, thereby freeing up memory and storage space. In this article, we will discuss in detail the knowledge and practice of cache conditional deletion in Java caching technology.

1. Definition of cache condition deletion

Cache condition deletion (Cache Eviction) means that when the cache data stored in the memory has reached certain restrictions, the system will use some algorithms to and conditions to proactively delete some cached data that is no longer needed or expired, thereby freeing up memory and storage space.

Of course, in actual applications, we may not necessarily need to wait until the memory reaches the upper limit before performing conditional deletion. In fact, we usually set some thresholds or time limits. After the storage time of cached data exceeds these limits, it will be regarded as expired data and then conditionally deleted.

2. Cache condition deletion algorithm

In Java cache technology, the common cache condition deletion algorithms are as follows:

1. First in, first out (FIFO) ) Algorithm

The first-in-first-out algorithm refers to the data that enters the cache first as the first data to be deleted. The implementation of this algorithm is relatively simple. You can use a queue to maintain the order of adding cached data, and then delete the data according to the order of the queue. The disadvantage is that this algorithm does not consider data usage and may result in the deletion of some frequently used data.

2. Least recently used (LRU) algorithm

The least recently used algorithm refers to deleting the least recently used data. The implementation of this algorithm requires maintaining a record of access time, and whenever data is accessed, the access time of the corresponding data is updated. When deleting data, just find the least recently used data. The disadvantage is that this algorithm may cause some data that has not been accessed for a long time to remain in the cache.

3. Least Frequently Used (LFU) Algorithm

The Least Frequently Used Algorithm refers to deleting the least frequently used data. The implementation of this algorithm requires maintaining a record of access counts, and whenever data is accessed, the access count of the corresponding data is increased. When deleting data, just find the data with the lowest access count. The disadvantage is that this algorithm may cause some data that has not been accessed for a long time to remain in the cache.

4. Random (Random) algorithm

Random algorithm refers to randomly selecting a piece of data to delete. The implementation of this algorithm is relatively simple. You only need to randomly select a piece of data in the cache to delete. The disadvantage is that this algorithm does not consider data usage and may delete some frequently used data.

3. Practice of realizing cache condition deletion

In practical applications, we can implement the cache condition deletion mechanism in Java cache technology through the following steps:

1. Set the cache cleaning time

By setting the cache cleaning time, the system can automatically delete expired data within a certain period of time. Here we can use @CacheEvict in the Spring Cache annotation to achieve this. The sample code is as follows:

@CacheEvict(value = "users", allEntries = true, beforeInvocation = true)
public void clearCache() {
    // do nothing, just clear cache
}

Here we set the value attribute to users, which means cleaning the cache data of users type. The allEntries attribute is set to true, which means clearing all data in the cache. The beforeInvocation attribute is set to true, which means that the cache cleaning operation is performed before the method is called.

2. Set cache size

By setting the cache size, you can allow the system to automatically delete some useless data when the cache data reaches a certain size. Here we can use @CacheConfig in the Spring Cache annotation to set the cache size. The sample code is as follows:

@CacheConfig(cacheNames = "users", cacheManager = "cacheManager")
public class UserServiceImpl implements UserService {
    @Autowired
    private UserRepository userRepository;

    @Cacheable(key = "#id")
    public User getUserById(Long id) {
        // ...
    }
}

Here we set the cacheNames attribute to users, which means setting the configuration information of users cache. Through Spring CacheManager, we can set parameters such as the maximum capacity and survival time of the cache, so as to realize the automatic cleaning function of the cache.

3. Select deletion algorithm

According to different application scenarios and cache data characteristics, we can choose different cache condition deletion algorithms. Generally speaking, the LRU and LFU algorithms can balance cache storage and deletion better. If there is some frequently accessed data in the application, you can give priority to the LFU algorithm; if the data access in the application is relatively randomly distributed, you can consider using the LRU algorithm.

4. Conclusion

The cache condition deletion mechanism is an important means in Java cache technology, which allows us to manage and utilize cached data more efficiently in applications. When implementing cache condition deletion, we need to choose appropriate cleaning strategies and algorithms to maintain the most effective use of cached data. The algorithms mentioned here are just some commonly used implementation methods. We can choose or customize other algorithms according to actual needs to meet the needs of the application.

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