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