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

spring-aop/scripts/demo-broken-gallery.sh

@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+# The broken-aspect gallery: six aspects that do not fire, and why.
+set -euo pipefail
+set +m
+cd "$(dirname "$0")/.."
+source scripts/env.sh
+{
+  echo "== aspects that do not fire =="
+  echo
+  start_app > /dev/null
+  curl -s "http://127.0.0.1:${APP_PORT}/aop/broken" | python3 -m json.tool
+  echo
+  echo "Reading it:"
+  echo
+  echo "  1 @Aspect without @Component  - the class is never instantiated, so the pointcut"
+  echo "                                  is never registered. No warning is produced."
+  echo "  2 pointcut typo               - 'com.ankurm.aop.services' (plural) parses fine and"
+  echo "                                  matches nothing. An empty match set is not an error."
+  echo "  3 private method              - cannot be overridden, so cannot be intercepted."
+  echo "  4 final method                - CGLIB subclasses; a final method is inherited, not"
+  echo "                                  overridden. Note beanIsProxied is still true."
+  echo "  5 self-invocation             - innerAdvisedWhenCalledFromOuter is false and"
+  echo "                                  innerAdvisedWhenCalledDirectly is true. Same method,"
+  echo "                                  same advice: only the call path differs."
+  echo "  6 created with new            - no container, no proxy, no advice."
+  stop_app
+} > docs/output/03-broken-gallery.txt 2>&1
+cat docs/output/03-broken-gallery.txt

spring-aop/scripts/demo-designators.sh

@@ -0,0 +1,48 @@
+#!/usr/bin/env bash
+# Every pointcut designator Spring AOP supports, with what it actually matched.
+set -euo pipefail
+set +m
+cd "$(dirname "$0")/.."
+source scripts/env.sh
+{
+  echo "== which designator matched which join point =="
+  echo
+  echo "Five methods are called once each: OrderService.place, OrderService.cancel,"
+  echo "InventoryService.reserve, InventoryService.finalCheck and"
+  echo "DefaultOrderService.interfaceless."
+  echo
+  start_app > /dev/null
+  curl -s "http://127.0.0.1:${APP_PORT}/aop/designators" | python3 -c '
+import json,sys
+d=json.load(sys.stdin)
+print("  orderService proxy kind :", d["orderServiceProxyKind"])
+print("  proxy is an instance of DefaultOrderService :",
+      d["orderServiceIsDefaultOrderServiceInstance"])
+print()
+for k,v in d["matches"].items():
+    print("  %-32s -> %s" % (k, ", ".join(v)))'
+  echo
+  echo "== what the parser accepts and refuses =="
+  echo
+  curl -s "http://127.0.0.1:${APP_PORT}/aop/parser" | python3 -c '
+import json,sys
+d=json.load(sys.stdin)
+print("  supported (all parsed and evaluated):")
+for r in d["supported"]:
+    print("    %-52s %s" % (r["expression"], "OK" if r["accepted"] else "REJECTED"))
+print()
+print("  unsupported in Spring AOP:")
+for r in d["unsupported"]:
+    print("    %-52s %s" % (r["expression"][:50], "accepted!" if r["accepted"] else "rejected"))
+print()
+first=[r for r in d["unsupported"] if not r["accepted"]][0]
+print("  the exception, in full:")
+print("    " + first["exception"])
+print("    " + first["message"])'
+  echo
+  echo "The reference documentation says these produce an IllegalArgumentException. They do"
+  echo "not: UnsupportedPointcutPrimitiveException extends RuntimeException directly, so a"
+  echo "catch of IllegalArgumentException will not catch it."
+  stop_app
+} > docs/output/01-designators.txt 2>&1
+cat docs/output/01-designators.txt

spring-aop/scripts/demo-proxy-types.sh

@@ -0,0 +1,56 @@
+#!/usr/bin/env bash
+# JDK dynamic proxies versus CGLIB, and what changes when you switch.
+#
+# Spring Boot sets spring.aop.proxy-target-class=true by default, so beans are proxied by
+# CGLIB even when they implement an interface. Setting it to false restores the framework's
+# own default and changes which designators match -- the same aspects, different results.
+set -euo pipefail
+set +m
+cd "$(dirname "$0")/.."
+source scripts/env.sh
+
+snapshot() {
+  curl -s "http://127.0.0.1:${APP_PORT}/aop/proxies" | python3 -c '
+import json,sys
+for r in json.load(sys.stdin):
+    print("  %-22s %-18s target=%s" % (r["bean"], r["proxyKind"], r["targetClass"].split(".")[-1]))
+    print("      class      : %s" % r["class"].split(".")[-1])
+    print("      interfaces : %s" % (", ".join(r.get("proxiedInterfaces") or []) or "(none)"))
+    print("      advisors   : %d" % r.get("advisorCount", 0))'
+  echo
+  curl -s "http://127.0.0.1:${APP_PORT}/aop/designators" | python3 -c '
+import json,sys
+d=json.load(sys.stdin)
+print("  proxy is an instance of DefaultOrderService :",
+      d["orderServiceIsDefaultOrderServiceInstance"])
+for k in ("this(OrderService)","target(DefaultOrderService)","bean(*OrderService)"):
+    print("    %-30s -> %s" % (k, ", ".join(d["matches"].get(k, ["(no match)"]))))'
+}
+
+{
+  echo "== Spring Boot default: spring.aop.proxy-target-class=true =="
+  echo "\$ java -jar $JAR"
+  echo
+  start_app > /dev/null
+  snapshot
+  echo
+  echo "== framework default restored: spring.aop.proxy-target-class=false =="
+  echo "\$ java -jar $JAR --spring.aop.proxy-target-class=false"
+  echo
+  start_app --spring.aop.proxy-target-class=false > /dev/null
+  snapshot
+  echo
+  echo "Same aspects, same beans, different proxy strategy:"
+  echo
+  echo " - With CGLIB the proxy is a SUBCLASS of DefaultOrderService, so it is an instance of"
+  echo "   the implementation class and methods that are not on the interface are advised."
+  echo " - With a JDK proxy the proxy implements OrderService only. It is NOT an instance of"
+  echo "   DefaultOrderService, casting to that class throws ClassCastException, and any"
+  echo "   method absent from the interface is invisible to advice."
+  echo
+  echo "This is why this() and target() differ. this() tests the proxy; target() tests the"
+  echo "object behind it. Under CGLIB they usually agree, which is exactly why the"
+  echo "distinction only bites after somebody switches the proxy type."
+  stop_app
+} > docs/output/02-proxy-types.txt 2>&1
+cat docs/output/02-proxy-types.txt

spring-aop/scripts/demo-versions.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+set -euo pipefail
+cd "$(dirname "$0")/.."
+source scripts/env.sh
+{
+  echo "== versions =="
+  java -version 2>&1 | clean
+  echo
+  echo "spring-boot-starter-parent: $(grep -A2 '<artifactId>spring-boot-starter-parent' pom.xml | grep '<version>' | sed 's/.*<version>\(.*\)<\/version>.*/\1/')"
+  echo "aspectjweaver:              $(find ~/.m2/repository -name 'aspectjweaver-*.jar' | sed 's/.*aspectjweaver-//;s/\.jar//' | sort | tail -1)"
+  echo
+  echo "== the Boot 4 starter rename =="
+  echo "spring-boot-starter-aop     last published: 4.0.0-M2   (last GA 3.5.16)"
+  echo "spring-boot-starter-aspectj first published: 4.0.0-M3"
+} > docs/output/00-versions.txt 2>&1
+cat docs/output/00-versions.txt

spring-aop/scripts/env.sh

@@ -0,0 +1,61 @@
+#!/usr/bin/env bash
+# Shared environment. Point JAVA_HOME at a JDK 25 (or newer) installation.
+: "${JAVA_HOME:?set JAVA_HOME to a JDK 25+ installation}"
+export PATH="$JAVA_HOME/bin:$PATH"
+MVN="${MVN:-mvn}"
+JAR="target/spring-aop-demo-1.0.0.jar"
+APP_MAIN="com.ankurm.aop.AopApplication"
+APP_PORT="${APP_PORT:-8080}"
+
+# Strip environment noise that is an artefact of the machine, not of Spring:
+# the JVM prints a JAVA_TOOL_OPTIONS banner to stderr on every launch when a proxy
+# truststore is configured, and it would otherwise end up in every committed transcript.
+clean() { grep -v "Picked up JAVA_TOOL_OPTIONS" | grep -v "^OpenJDK 64-Bit Server VM warning"; }
+
+# Start the demo jar detached, record its PID, and block until it answers.
+# Extra arguments are passed to the application. Environment variables for the run are
+# passed by setting them on the call: `APP_ENV="A=1 B=2" start_app --spring.profiles.active=x`
+start_app() {
+  stop_app
+  mkdir -p target
+  # Deliberately NOT setsid: setsid forks when it is not already a process-group leader,
+  # so $! would be the PID of a process that exits immediately and the JVM would survive
+  # every later stop_app. A surviving JVM keeps the port, the next scenario fails to bind,
+  # and curl answers from the previous scenario -- which reads exactly like the
+  # configuration change under test having had no effect. Three wrong findings in this
+  # repository came from that before it was tracked down.
+  if [ -n "${APP_ENV:-}" ]; then
+    # shellcheck disable=SC2086
+    env $APP_ENV nohup java -jar "$JAR" "$@" > /tmp/aop-demo.log 2>&1 < /dev/null &
+  else
+    nohup java -jar "$JAR" "$@" > /tmp/aop-demo.log 2>&1 < /dev/null &
+  fi
+  echo $! > target/app.pid
+  for _ in $(seq 1 60); do
+    curl -s -o /dev/null "http://127.0.0.1:${APP_PORT}/aop/proxies" 2>/dev/null && return 0
+    kill -0 "$(cat target/app.pid)" 2>/dev/null || { echo "JVM exited during startup:"
+      tail -20 /tmp/aop-demo.log; return 1; }
+    sleep 1
+  done
+  echo "application did not answer"; tail -20 /tmp/aop-demo.log; return 1
+}
+
+# Stop it by recorded PID. Never by pattern: `ps | grep <jar name>` also matches the shell
+# running the script, because the jar name is on that shell's own command line.
+stop_app() {
+  if [ -f target/app.pid ]; then
+    pid=$(cat target/app.pid)
+    if [ -n "$pid" ] && grep -qa "spring-aop-demo" "/proc/$pid/cmdline" 2>/dev/null; then
+      kill -9 "$pid" 2>/dev/null || true
+      wait "$pid" 2>/dev/null || true      # reap, so bash prints no "Killed" notice
+    fi
+    rm -f target/app.pid
+  fi
+  for _ in $(seq 1 40); do
+    if ! (exec 3<>/dev/tcp/127.0.0.1/"${APP_PORT:-8080}") 2>/dev/null; then break; fi
+    sleep 0.25
+  done
+  exec 3<&- 2>/dev/null || true
+}
+
+# Print the precedence report for one property, compactly.

spring-aop/scripts/run-all.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+# Regenerate every transcript under docs/output/.
+set -euo pipefail
+cd "$(dirname "$0")/.."
+source scripts/env.sh
+
+"$MVN" -B -q package -DskipTests
+
+for demo in versions designators proxy-types broken-gallery; do
+  echo "=== $demo ==="
+  "scripts/demo-$demo.sh" > /dev/null
+done
+stop_app
+echo
+echo "regenerated:"
+ls -1 docs/output/