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/docs/08-diagnosing-a-value.md

@@ -0,0 +1,57 @@
+[← IDE metadata](07-ide-metadata.md) · [Index](../README.md)
+
+# 8. Diagnosing a value
+
+Endpoint: [`BindingDiagnosticsEndpoint`](../src/main/java/com/ankurm/configprops/web/BindingDiagnosticsEndpoint.java).
+
+"The property is set but the application does not see it" is the most common configuration bug,
+and it is hard for one reason: a value carries no visible provenance. Spring Boot tracks it
+anyway — every property loaded from a file or a config tree carries an `Origin` naming the
+resource and the line.
+
+```
+$ curl -s 'localhost:8080/diag/origin?name=demo.mail.host'
+{
+  "property": "demo.mail.host",
+  "effectiveValue": "smtp.example.com",
+  "candidatesInPrecedenceOrder": [
+    {
+      "source": "OriginTrackedMapPropertySource {name='Config resource ... [application.yaml]'}",
+      "value": "smtp.example.com",
+      "origin": "class path resource [application.yaml] - 15:11"
+    }
+  ]
+}
+```
+
+Line 15, column 11. Not "somewhere in your configuration".
+
+## How it works
+
+```java
+for (ConfigurationPropertySource source : ConfigurationPropertySources.get(environment)) {
+    ConfigurationProperty property =
+            source.getConfigurationProperty(ConfigurationPropertyName.of(name));
+    if (property != null) {
+        // property.getValue(), property.getOrigin(), source.getUnderlyingSource()
+    }
+}
+```
+
+Iterating `ConfigurationPropertySources.get(...)` gives you the sources in precedence order.
+The first hit is the winner; everything after it exists and lost. A property with several
+holders is exactly what "my change had no effect" looks like from the inside — and the
+[profiles project](../../profiles-and-config) is entirely about that case.
+
+## Delete it before shipping
+
+This endpoint prints whatever a mounted secret contains. If you want it permanently, put it
+behind the management port and authentication, or use Actuator's `/actuator/env`, which does
+the same job with sanitisation built in.
+
+## Without an endpoint
+
+- `--debug` prints the auto-configuration report, not property origins.
+- Setting `logging.level.org.springframework.boot.context.config=TRACE` logs which config data
+  resources were loaded, in order — useful when the question is "was my file read at all".
+- In a test, inject `Environment` and inspect `getPropertySources()` directly.