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

configuration-properties/scripts/demo-env-binding.sh

@@ -0,0 +1,52 @@
+#!/usr/bin/env bash
+# The matrix re-asked the expensive way: one real JVM per spelling, the value supplied by the
+# operating system or by -D, and read back through both @ConfigurationProperties and @Value.
+#
+# This script exists because the in-process matrix was wrong twice before it was right. A
+# synthesised property source is not a running Spring Boot application, and when the two
+# disagree the running application wins.
+set -euo pipefail
+cd "$(dirname "$0")/.."
+source scripts/env.sh
+
+RUN=(java -jar "$JAR" --spring.profiles.active=envprobe
+     --spring.main.web-application-type=none --spring.main.banner-mode=off
+     --logging.level.root=OFF)
+
+run_env() {
+  echo "\$ $1=secret-value java -jar $JAR"
+  env -u DEMO_RELAXED_API_KEY -u DEMO_RELAXED_APIKEY "$1=secret-value" "${RUN[@]}" 2>&1 \
+    | clean | grep -E "^(env-var-set|@Config|@Value|Environment)"
+  echo
+}
+
+run_sysprop() {
+  echo "\$ java -D$1=secret-value -jar $JAR"
+  env -u DEMO_RELAXED_API_KEY -u DEMO_RELAXED_APIKEY \
+    java "-D$1=secret-value" -jar "$JAR" --spring.profiles.active=envprobe \
+      --spring.main.web-application-type=none --spring.main.banner-mode=off \
+      --logging.level.root=OFF 2>&1 \
+    | clean | grep -E "^(@Config|@Value|Environment)"
+  echo
+}
+
+{
+  echo "== real process, real environment: binding demo.relaxed.api-key =="
+  echo
+  echo "canonical property : demo.relaxed.api-key"
+  echo "(MISS) means the property was not found and the declared default was used"
+  echo
+  echo "--- as an operating-system environment variable ---"
+  echo
+  run_env DEMO_RELAXED_API_KEY
+  run_env DEMO_RELAXED_APIKEY
+  echo "--- as a JVM system property (-D), i.e. the 'map' rows of the matrix ---"
+  echo
+  run_sysprop demo.relaxed.api-key
+  run_sysprop demo.relaxed.apiKey
+  run_sysprop demo.relaxed.apikey
+  run_sysprop demo.relaxed.api.key
+  echo "The last one is not a spelling of the property. api.key is two name elements;"
+  echo "api-key is one. Nothing relaxed will ever join them."
+} > docs/output/02-env-var-binding.txt 2>&1
+cat docs/output/02-env-var-binding.txt