Cache closing mechanism in Java caching technology

In Java development, caching is one of the important means to improve application performance. Caching can reduce the application's access pressure on back-end storage resources such as databases and speed up response times. At the same time, caching can also reduce the impact of network latency or bandwidth bottlenecks on application performance. However, there are some problems with caching. Especially when the cached content expires or there is a problem with the storage resource, the cached data may be inaccurate or invalid. Therefore, during the use of cache, it is necessary to take some measures to close the cache to avoid problems caused by cache.

The Java cache closing mechanism refers to how to automatically close the cache when there is a problem with the cache. There are two main ways to turn off caching: manual turning off and automatic turning off.

Manually closing the cache mechanism refers to manually closing the cache through the API in Java code.

The automatic closing cache mechanism refers to setting the cache expiration time and data capacity in the cache configuration, and closing the cache when specific conditions are met, such as when the cache size exceeds a certain threshold or the cached data expires. . Automatically closing the cache mechanism generally requires the use of relevant functions of the cache framework.

Next, this article will introduce the cache closing mechanism in Java cache technology in detail.

1. Manually close the cache

The main way to manually close the cache is to manually close the cache through the API.

In Java, caching is usually implemented using a caching framework, such as Ehcache, Redis, Memcached, etc. Taking Ehcache as an example, Ehcache provides a CacheManager class to manage the cache. You can use this class to obtain the cache object, and then close the cache by operating on the cache object.

The following is a code example to turn off the cache:

//获取CacheManager对象
CacheManager cacheManager = CacheManager.getInstance();

//获取缓存对象
Cache cache = cacheManager.getCache("myCache");

//关闭缓存
cacheManager.removeCache("myCache");

In the above code, the CacheManager object is first obtained through the CacheManager.getInstance() method. Then, the cache object named "myCache" is obtained through the cacheManager.getCache() method. Finally, turn off the cache through the cacheManager.removeCache() method.

2. Automatically close the cache

Automatically closing the cache generally requires the use of related functions of the cache framework.

Take Ehcache as an example. Ehcache provides two ways to automatically close the cache: automatically close according to the cache capacity and automatically close according to the expiration time of the cache element.

1. Automatically close the cache according to the cache capacity

In Ehcache, you can set the size of the cache. When the number of cache items generated in the cache reaches a certain number, you need to Automatically turn off the cache to prevent the cache from taking up too much memory and affecting application performance. The maximum number of elements can be set using the maxElementsInMemory property.

Ehcache provides two cache eviction strategies to manage cached elements. When the number of cache elements reaches the maximum size limit, some cache elements need to be evicted. Ehcache provides the following two cache eviction strategies:

(1) LRU eviction strategy: Least Recently Used, least recently used. Select the objects that have not been used for the longest period of time to clear.

(2) FIFO eviction strategy: First In First Out, first in, first out. Objects are cleared in the order in which they were entered into the cache.

The following is an example of a configuration file that automatically turns off the cache size:

<ehcache>
    <cache name="myCache"
       maxEntriesLocalHeap="10000"
       maxEntriesLocalDisk="1000"
       eternal="false"
       diskSpoolBufferSizeMB="20"
       timeToIdleSeconds="300" timeToLiveSeconds="600"
       memoryStoreEvictionPolicy="LFU">
    </cache>
</ehcache>

In the above configuration file, the maximum number of elements in the cache is set to 10,000 through the maxEntriesLocalHeap attribute. When the number of elements stored in the cache exceeds 10,000, Ehcache will automatically close the cache.

2. Automatically close the cache based on the expiration time of the cache element

In Ehcache, you can set the maximum survival time and minimum survival time of each element in the cache. When the maximum or minimum survival time of an element in the cache exceeds the preset time, the element will be deleted from the cache. You can use the timeToLiveSeconds attribute to set the maximum live time of each element in the cache, and the timeToIdleSeconds attribute to set the minimum live time of each element in the cache.

The following is an example of a configuration file that automatically closes the cache time:

<ehcache>
    <cache name="myCache"
       maxEntriesLocalHeap="10000"
       maxEntriesLocalDisk="1000"
       eternal="false"
       diskSpoolBufferSizeMB="20"
       timeToIdleSeconds="300" timeToLiveSeconds="600"
       memoryStoreEvictionPolicy="LFU">
    </cache>
</ehcache>

In the above configuration file, the minimum survival time of each element in the cache is set to 300 seconds through the timeToIdleSeconds attribute, which is set through the timeToLiveSeconds attribute The maximum survival time of each element in the cache is 600 seconds. When the maximum or minimum survival time of an element in the cache exceeds the preset time, the element will be deleted from the cache, thereby automatically closing the cache.

3. Summary

The cache closing mechanism is an important issue in Java cache technology. In Java, two mechanisms, manual closing and automatic closing, can be used to achieve cache closing. Manually closing the cache is to manually close the cache through the API and needs to be implemented in the code. Automatically closing the cache generally requires the use of related functions of the cache framework. Ehcache provides two mechanisms to automatically close the cache: automatically close based on cache capacity and automatically close based on the expiration time of cache elements. The method of automatically closing the cache based on the cache capacity is simple, but the parameters need to be set appropriately according to the actual situation; the method of automatically closing the cache based on the expiration time of the cache element is more flexible, but it may happen that the cache element has expired but has not expired. Therefore, when using the cache closing mechanism, you need to make a flexible choice based on the actual situation.

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