Three new article modules: configuration binding, profiles and config data, Spring AOP

configuration-properties/  @ConfigurationProperties vs @Value on Spring Boot 4.1.1.
  The relaxed-binding matrix is generated by binding each spelling rather than
  transcribed, and re-checked against real processes -- the in-process probe was
  wrong twice before it was right. Records the three findings that came out of it:
  @Value does get relaxed resolution inside Spring Boot (Boot attaches
  ConfigurationPropertySources), the configuration processor silently stops
  generating metadata on JDK 23+ when declared as a plain dependency, and @Valid is
  not what makes nested constraints run.

profiles-and-config/       Precedence, profiles, spring.config.import and config trees.
  /precedence reports every source holding a property in rank order with file and
  line, which turns "my profile file had no effect" into a two-line answer. Also
  pins the counterintuitive one: an imported file outranks the file that imported it.

spring-aop/                Designators, proxy types, and aspects that do not fire.
  One advice per supported designator so the reference table is generated from real
  matches; all fourteen unsupported designators fed to the parser. Two corrections to
  the reference documentation: unsupported designators throw
  UnsupportedPointcutPrimitiveException (extends RuntimeException, not
  IllegalArgumentException), and spring-boot-starter-aop was renamed to
  spring-boot-starter-aspectj in Boot 4.

19 contract tests across the three modules, 15 captured transcripts, all regenerated
by scripts/run-all.sh. Verified on Spring Boot 4.1.1, Spring Framework 7.0.9,
JDK 25.0.4.1.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Gip4srpzMwjgoba6uEfbr5

profiles-and-config/docs/05-config-import.md

@@ -0,0 +1,58 @@
+[← Why your profile file lost](04-why-your-profile-file-lost.md) · [Index](../README.md) · [Config trees →](06-config-trees-and-configmaps.md)
+
+# 5. `spring.config.import`
+
+Transcript: [`04-import-and-multidoc.txt`](output/04-import-and-multidoc.txt).
+
+```yaml
+spring:
+  config:
+    import: "optional:classpath:/imported.yaml"
+```
+
+## The imported file wins
+
+This is the part that catches people, and it catches them in the direction opposite to the one
+they brace for:
+
+```
+  effective value : from-imported-yaml
+    1. from-imported-yaml            <- imported.yaml
+    2. from-application-import-yaml  <- application-import.yaml   (declared the import)
+    3. from-application-yaml         <- application.yaml
+```
+
+The importing file declared the import and then lost to it. An imported document is processed
+*after* the document that declared it, and later documents win.
+
+`#include` semantics would give the opposite. So would treating the import as a set of
+defaults, which is what people usually intend when they import a shared baseline. If you import
+a company-wide `common.yaml` expecting your own file to override it, every key `common.yaml`
+sets will quietly beat yours.
+
+To get defaults-style behaviour, put your overrides somewhere that outranks config data — an
+environment variable or a command-line argument — or import from a *later* document in your own
+file so the ordering is explicit.
+
+## Prefixes
+
+| Prefix | Meaning |
+|---|---|
+| `optional:` | do not fail if it is missing |
+| `file:` | a filesystem path |
+| `classpath:` | a classpath resource |
+| `configtree:` | a directory of value-per-file entries |
+
+They compose: `optional:configtree:/etc/config/`.
+
+Without `optional:`, a missing location is `ConfigDataLocationNotFoundException` at startup.
+That is usually what you want for a secret mount and never what you want for a developer
+machine.
+
+## Where imports are legal
+
+`spring.config.import` is only honoured in config data — `application.yaml` and friends. Setting
+it as an environment variable or a command-line argument works too, because those are processed
+before config data is loaded. Setting it anywhere else does nothing.
+
+Imports are processed depth-first, and a cycle is detected and reported rather than looping.