Ankur Mhatre
86246dc860
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
@ConfigurationProperties vs @Value
Companion project for @ConfigurationProperties vs @Value in Spring Boot 4 on ankurm.com.
Every table and transcript quoted in that article was produced by running something here. Three of them were produced twice, because the first answer was wrong — see chapter 2.
Versions
| Spring Boot | 4.1.1 |
| Spring Framework | 7.0.9 |
| JDK | Eclipse Temurin 25.0.4.1 (LTS) |
| Validation | Hibernate Validator via spring-boot-starter-validation |
Quickstart
export JAVA_HOME=/path/to/jdk-25
mvn -DskipTests package
./scripts/run-all.sh # regenerate every transcript in docs/output/
mvn test # 7 contract tests
Profiles
| Profile | What it does |
|---|---|
| (none) | binds demo.* from application.yaml |
probe |
runs the relaxed-binding matrix and exits |
envprobe |
reports one property as seen by the binder and by @Value |
badvalidation |
values that violate every constraint, so startup fails |
csvlist |
the recipients list as a comma-separated string |
Endpoints
| Endpoint | Purpose |
|---|---|
GET /diag/bound |
the bound objects, and the same values via @Value |
GET /diag/origin?name= |
every source holding a property, in precedence order, with file and line |
Both are diagnostics. Delete them before shipping.
Documentation
- Two mechanisms, not two styles
- Relaxed binding, measured
- Getting the bean registered
- Records, constructor binding and defaults
- Validation
- When
@Valueis still the right answer - IDE metadata, and the JDK 23 change that silently breaks it
- Diagnosing a value
Captured output
| File | Produced by |
|---|---|
00-versions.txt |
scripts/demo-versions.sh |
01-relaxed-matrix.txt |
scripts/demo-relaxed-matrix.sh |
02-env-var-binding.txt |
scripts/demo-env-binding.sh |
03-value-vs-binding.txt |
scripts/demo-value-vs-binding.sh |
04-validation-failure.txt |
scripts/demo-validation.sh |
05-metadata-generation.txt |
scripts/demo-metadata-generation.sh |
Three findings worth the trip
@Valuegets relaxed binding inside Spring Boot. The universal claim that it does not is a statement about the Spring Framework; Boot attaches a property source that changes it.- The configuration processor silently stops on JDK 23+ when declared as a plain dependency, so IDE auto-completion quietly dies while the build stays green.
@Validis not what makes nested constraints run. Boot'sValidationBindHandlervalidates every object it binds.