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
52 lines
2.3 KiB
Markdown
52 lines
2.3 KiB
Markdown
[Index](../README.md) · [Designators →](02-designators.md)
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# 1. What Spring AOP actually is
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Spring AOP is a **proxy** mechanism that borrows AspectJ's **pointcut language**. Both halves
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of that sentence explain a failure mode.
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## It is proxies
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Spring does not modify your bytecode. When a bean matches a pointcut, the container puts a
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proxy in the bean registry in its place. Callers get the proxy; the proxy runs advice and then
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forwards to the real object.
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Everything that follows from this:
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- Only **beans** can be advised. An object created with `new` has no proxy.
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- Only calls **through the proxy** are intercepted. A call the object makes to itself is not.
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- Only **overridable** methods can be advised: not private, not final, not static.
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- Join points are **method executions**. Field access, constructor calls and exception handlers
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are not available, no matter what the pointcut language allows you to write.
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## It borrows the pointcut language
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`aspectjweaver` on the classpath supplies the pointcut *parser*. Spring uses it to decide which
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methods match and then does its own weaving with proxies. AspectJ's own weaver is not involved.
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This is why the designator list is a subset: the language can express `call()` and `cflow()`,
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and a proxy cannot implement them. See [chapter 2](02-designators.md).
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## The Spring Boot 4 starter rename
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In Spring Boot 3 the dependency was `spring-boot-starter-aop`. In Spring Boot 4 it is
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**`spring-boot-starter-aspectj`**.
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```
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spring-boot-starter-aop last published 4.0.0-M2 (last GA: 3.5.16)
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spring-boot-starter-aspectj first published 4.0.0-M3
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```
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The contents are unchanged: `spring-boot-starter`, `spring-aop`, `aspectjweaver`. But the old
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artifact is no longer in the Boot BOM, so copying a dependency block out of any pre-4 tutorial
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fails resolution with a missing-version error rather than a helpful message.
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Without the starter, `@Aspect` classes are ordinary beans, no pointcut is ever parsed, and
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every aspect in the application silently matches nothing.
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## When to use something else
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If you need to advise field access, constructors, or calls between objects you do not own, you
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need real AspectJ weaving (compile-time or load-time), not Spring AOP. If you need to advise
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one internal call, you need to refactor — see [chapter 5](05-broken-aspect-gallery.md).
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