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spring-boot-demo/caching/docs/output/15-providers-and-ttl.txt
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asmhatre a9867c0423 Add caching: the Spring cache abstraction, keys, eviction timing and the self-invocation trap
A Spring Boot 4.1.1 module whose test suite is the evidence for the article: 20 tests
producing 22 transcripts under docs/output/, plus 12 documentation chapters.

Findings the build pins:
- @EnableCaching has no exposeProxy attribute; the widely-copied
  @EnableCaching(exposeProxy = true) does not compile.
- Two methods sharing a cache name and an argument type share a key space, and one
  silently serves the other's answers.
- The documented cache-provider detection order does not match CacheType's enum
  order in 4.1.1: COUCHBASE before INFINISPAN, and CACHE2K before CAFFEINE.
- beforeInvocation = true is NOT deferred by TransactionAwareCacheManagerProxy on
  7.0.9 - doEvict picks evictIfPresent, which the decorator does not intercept.
- Four of five invalid declarations start a clean context and throw at the first call.
- Caffeine on the classpath silently displaces the simple provider.
2026-09-12 05:35:13 +00:00

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# TTL and size bounds are the provider's job, not the abstraction's
cacheManager : org.springframework.cache.caffeine.CaffeineCacheManager
configured : expireAfterWrite=400ms, maximumSize=3, recordStats
two calls, same key, immediately -> 1 repository calls
one more call 600 ms later -> 2 repository calls <- the entry expired
--- size bound ---
five distinct keys written, maximumSize = 3
estimated size after eviction settles : 3
stats : hits=1 misses=5 evictions=3
--- recordStats is not on by default ---
a Caffeine cache built without recordStats(), after 1 hit and 1 miss:
CacheStats{hitCount=0, missCount=0, loadSuccessCount=0, loadFailureCount=0, totalLoadTime=0, evictionCount=0, evictionWeight=0}
Every counter is zero. Micrometer's cache.gets and cache.evictions will
exist and report zero too, which looks exactly like a cache nobody uses.
The Spring cache abstraction has no TTL, no size limit and no eviction
policy of its own - it is an interface over whatever you plug in. On the
default simple provider, a ConcurrentHashMap, an entry stays until something
evicts it by hand or the process ends.