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spring-boot-demo/caching/docs/output/10-nulls.txt
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asmhatre 66208bcd97 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: 19 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.
- 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 05:19:22 +00:00

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# A cached null is a real entry called NullValue
searchCachingNulls("xyz") returns null, called twice -> 1 invocations
cache "nulls":
key xyz -> null [org.springframework.cache.support.NullValue]
The abstraction stores org.springframework.cache.support.NullValue.INSTANCE
so a hit on null is distinguishable from a miss. This is usually what you
want - it is the cheap defence against a hot lookup for a row that is not
there - and occasionally exactly what you do not want.
--- unless = "#result == null" ---
searchNullable("xyz") twice -> 2 invocations <- the null was never stored
cache "terms":
(empty)