Cache validity period in Java caching technology

With the continuous development of computer applications, performance issues have always been a focus of attention in computer science. Caching, as one of the key technologies to improve system performance, has been widely used. In Java, caching technology has also been widely used, but cache validity period is an important factor to consider when using caching technology.

The cache validity period refers to the time that cached data is stored in the cache. After this time, the cached data will be automatically deleted or recalculated. Setting the cache validity period can not only control the timeliness of data in the cache, but also effectively avoid the impact of outdated data on system performance.

There are many ways to set the cache validity period in Java. Here are some introductions.

1. By setting system properties

You can control the cache validity period by setting the java.util.concurrent.* system properties. For example, you can set a cache with a global validity period of 30 seconds:

java -Dsun.util.cache.CachePermGenEntries=1000 
     -Dsun.util.cache.CachePermGenSoftRefs=true 
     -Dsun.util.cache.CachePermGenSize=2000 
     -Dsun.util.cache.CachePermGenExpire=30000 
     TestApplication

Among them, CachePermGenEntries and CachePermGenSize control the upper limit of the amount of data in the cache, CachePermGenSoftRefs controls whether soft references are used in the cache, and CachePermGenExpire controls the global cache validity period.

2. Using Guava Cache

Guava is a Java toolset developed by Google. The cache module supports the use of cache validity period to control the life cycle of cached data. You can use CacheBuilder to create a cache container and set the cache validity period in the constructor:

LoadingCache<String, String> cache = CacheBuilder.newBuilder()
        .expireAfterWrite(30, TimeUnit.SECONDS)
        .build(new CacheLoader<String, String>() {
            public String load(String key) {
                return "default_value";
            }
        });

Among them, the expireAfterWrite method specifies the validity period after writing to the cache.

3. Using Spring Cache

Spring also provides caching technology and supports the use of cache validity period to control the life cycle of cached data. The cache validity period can be set in the annotation @Cacheable:

@Cacheable(value = "cache_name", key = "#id", evict = false, expiration = 30)
public String get(String id) {
    return "cache_test";
}

The expiration parameter specifies the cache validity period in seconds.

To sum up, the cache validity period is an important factor to consider when using caching technology. There are many ways to set cache validity period in Java, and you can choose the appropriate method according to actual needs. At the same time, it is also important to note that when using caching technology, you must confirm that the cache validity period really needs to be controlled, otherwise the cached data may be deleted prematurely and increase unnecessary performance overhead.

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