Spring's caching abstraction is a thin, declarative layer over a pluggable cache provider — you annotate methods, Spring weaves an AOP proxy around them, and the proxy decides whether to call the method or short-circuit to a cached value. The abstraction itself stores nothing; it delegates to a CacheManager backed by Caffeine, Redis, Hazelcast, Ehcache, or a no-op ConcurrentHashMap. Your code stays provider-agnostic.
Turn it on with @EnableCaching on a @Configuration class — this registers the cache BeanPostProcessor that creates the AOP proxies. Without it, the annotations are inert.
@Configuration
@EnableCaching
class CacheConfig {
@Bean
CacheManager cacheManager() {
return new CaffeineCacheManager("books", "authors");
}
}
@Service
class BookService {
@Cacheable("books")
public Book findById(long id) { /* expensive DB call */ }
}The three core annotations map to three cache operations. @Cacheable is lookup-or-store: on a hit it returns the cached value and skips the method; on a miss it runs the method and stores the result. @CachePut always runs the method and writes the return value to the cache — the right tool for updates. @CacheEvict removes entries (allEntries = true clears the whole region). @Caching composes several of these on one method when a single annotation can't express the intent.
The proxy keys each entry. By default SimpleKeyGenerator builds a key from all method parameters; you override with SpEL via key = "#id" or a custom KeyGenerator bean. condition (evaluated on arguments, before the call) and unless (evaluated on the result, after) let you cache selectively.
Two failure modes dominate interviews: self-invocation — calling a @Cacheable method from within the same bean bypasses the proxy entirely, exactly like @Transactional — and cache stampede, where many concurrent misses recompute the same value at once.
The questions below cover the annotation set and composition, key generation, provider trade-offs, stampede prevention, conditional caching, the self-invocation trap, and end-to-end consistency strategies.