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/05-validation.md

@@ -0,0 +1,55 @@
+[← Records and defaults](04-records-and-defaults.md) · [Index](../README.md) · [When @Value wins →](06-when-value-still-wins.md)
+
+# 5. Validation
+
+Transcript: [`04-validation-failure.txt`](output/04-validation-failure.txt).
+Type: [`ValidatedProperties`](../src/main/java/com/ankurm/configprops/props/ValidatedProperties.java).
+
+This is the capability `@Value` does not have at all, and the reason to prefer binding for
+anything that can be misconfigured.
+
+## What it takes
+
+1. `spring-boot-starter-validation` on the classpath. Without a validator implementation,
+   `@Validated` is a no-op — nothing is checked and nothing says so.
+2. `@Validated` on the properties type.
+3. JSR-380 constraints on the components.
+
+## What you get
+
+A bad value becomes a startup failure that names the property, the offending value, the file
+and line it came from, and the constraint it broke — all of them at once, not one per restart:
+
+```
+Property: demo.validated.port
+Value: "99999"
+Origin: class path resource [application-badvalidation.yaml] - 6:11
+Reason: must be less than or equal to 65535
+```
+
+The alternative is a `NumberFormatException` in a request handler at 3am.
+
+## `@Valid` on nested types is not what makes them validate
+
+The rule "annotate nested properties with `@Valid` or their constraints are ignored" is widely
+repeated and does not apply here. It is true of ordinary bean validation, where cascading is
+opt-in. Spring Boot's `ValidationBindHandler` validates *every object the binder finishes
+constructing*, nested ones included.
+
+`BindingContractTests.nestedConstraintsFireWithoutValid` pins this: a nested record carrying
+`@Max(100)` and no `@Valid` anywhere in the type still fails the bind at 4000. That test was
+originally written to assert the opposite and failed, which is how it ended up documented here.
+
+Keep writing `@Valid` if you like — it is harmless and it is what a reader expects. Just do not
+believe it is load-bearing.
+
+## Ordering
+
+The violation order in the failure report is not stable between runs. Do not write a test that
+asserts on it.
+
+## Custom validation
+
+For rules a constraint annotation cannot express — "if `mode` is `remote` then `endpoint` is
+required" — implement `Validator` and expose it as a bean named `configurationPropertiesValidator`.
+It runs at bind time with the same reporting.