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
77 lines
3.1 KiB
Markdown
77 lines
3.1 KiB
Markdown
# @ConfigurationProperties vs @Value
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Companion project for [**@ConfigurationProperties vs @Value in Spring Boot 4**](https://ankurm.com/)
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on ankurm.com.
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Every table and transcript quoted in that article was produced by running something here.
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Three of them were produced twice, because the first answer was wrong — see
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[chapter 2](docs/02-relaxed-binding.md).
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## Versions
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| Spring Boot | 4.1.1 |
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| Spring Framework | 7.0.9 |
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| JDK | Eclipse Temurin 25.0.4.1 (LTS) |
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| Validation | Hibernate Validator via `spring-boot-starter-validation` |
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## Quickstart
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```bash
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export JAVA_HOME=/path/to/jdk-25
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mvn -DskipTests package
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./scripts/run-all.sh # regenerate every transcript in docs/output/
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mvn test # 7 contract tests
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```
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## Profiles
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| Profile | What it does |
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| *(none)* | binds `demo.*` from `application.yaml` |
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| `probe` | runs the relaxed-binding matrix and exits |
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| `envprobe` | reports one property as seen by the binder and by `@Value` |
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| `badvalidation` | values that violate every constraint, so startup fails |
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| `csvlist` | the recipients list as a comma-separated string |
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## Endpoints
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| Endpoint | Purpose |
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| `GET /diag/bound` | the bound objects, and the same values via `@Value` |
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| `GET /diag/origin?name=` | every source holding a property, in precedence order, with file and line |
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Both are diagnostics. Delete them before shipping.
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## Documentation
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1. [Two mechanisms, not two styles](docs/01-two-mechanisms.md)
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2. [Relaxed binding, measured](docs/02-relaxed-binding.md)
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3. [Getting the bean registered](docs/03-registration.md)
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4. [Records, constructor binding and defaults](docs/04-records-and-defaults.md)
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5. [Validation](docs/05-validation.md)
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6. [When `@Value` is still the right answer](docs/06-when-value-still-wins.md)
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7. [IDE metadata, and the JDK 23 change that silently breaks it](docs/07-ide-metadata.md)
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8. [Diagnosing a value](docs/08-diagnosing-a-value.md)
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## Captured output
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| File | Produced by |
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| [`00-versions.txt`](docs/output/00-versions.txt) | `scripts/demo-versions.sh` |
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| [`01-relaxed-matrix.txt`](docs/output/01-relaxed-matrix.txt) | `scripts/demo-relaxed-matrix.sh` |
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| [`02-env-var-binding.txt`](docs/output/02-env-var-binding.txt) | `scripts/demo-env-binding.sh` |
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| [`03-value-vs-binding.txt`](docs/output/03-value-vs-binding.txt) | `scripts/demo-value-vs-binding.sh` |
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| [`04-validation-failure.txt`](docs/output/04-validation-failure.txt) | `scripts/demo-validation.sh` |
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| [`05-metadata-generation.txt`](docs/output/05-metadata-generation.txt) | `scripts/demo-metadata-generation.sh` |
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## Three findings worth the trip
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- **`@Value` gets relaxed binding inside Spring Boot.** The universal claim that it does not is
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a statement about the Spring Framework; Boot attaches a property source that changes it.
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- **The configuration processor silently stops on JDK 23+** when declared as a plain
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dependency, so IDE auto-completion quietly dies while the build stays green.
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- **`@Valid` is not what makes nested constraints run.** Boot's `ValidationBindHandler`
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validates every object it binds.
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