spring-boot-demo/custom-validation/docs/01-jakarta-namespace-and-bean-validation-3-1.md

1. The jakarta.validation namespace, and what Bean Validation 3.1 actually changed

README | Next: Record validation

Source: ContactForm.java, SpamMessageCheck.java. Transcripts: docs/output/00-jakarta-validation-api-manifest.txt, docs/output/00b-hibernate-validator-manifest.txt.

The defect this module replaces

The original version of the companion article this module backs used javax.validation.constraints.NotBlank, javax.validation.Constraint, and so on throughout -- the pre-Jakarta-EE-9 namespace. That package was already wrong for any Spring Boot 3+ application by the time the article was first published: Spring Boot 3.0 moved its entire dependency tree from javax.* to jakarta.* in December 2022, and javax.validation.* classes are simply not on the classpath of a spring-boot-starter-validation 3.x or 4.x application. Every class in this module uses jakarta.validation.* instead. If you have a codebase still on javax.validation, it did not survive the Boot 2 to 3 upgrade and needs the same mechanical rename this module already reflects.

What Spring Boot 4.1.1 actually pins, checked directly

Rather than trust a blog's version claim (including an older draft of this one), the fact was checked the way this repository always checks it: build a throwaway project against spring-boot-starter-parent:4.1.1 and run mvn dependency:tree.

[INFO] +- org.springframework.boot:spring-boot-starter-validation:jar:4.1.1:compile
[INFO] |  \- org.springframework.boot:spring-boot-validation:jar:4.1.1:compile
[INFO] |     \- org.hibernate.validator:hibernate-validator:jar:9.1.3.Final:compile
[INFO] |        +- jakarta.validation:jakarta.validation-api:jar:3.1.1:compile

Then confirmed a second, independent way: open the actual jars this application loads at runtime and read their own manifests, rather than trusting the dependency tree's coordinates alone.

$ mvn test   # ClasspathVersionTest

Class: jakarta.validation.Validation
Jar file: jakarta.validation-api-3.1.1.jar
Bundle-SymbolicName: jakarta.validation.jakarta.validation-api
Bundle-Version: 3.1.1
Implementation-Version: null

(docs/output/00-jakarta-validation-api-manifest.txt)

Class: org.hibernate.validator.internal.engine.ValidatorFactoryImpl
Jar file: hibernate-validator-9.1.3.Final.jar
Implementation-Title: hibernate-validator
Implementation-Version: 9.1.3.Final

(docs/output/00b-hibernate-validator-manifest.txt)

Spring Boot 4.1.1 pins Hibernate Validator 9.1.3.Final, the reference implementation of Jakarta Validation 3.1 -- the spec revision released in 2024 as part of Jakarta EE 11.

What is actually new in 3.1 (not a rename of 3.0)

Three real changes, not a version-number bump for its own sake:

• The specification itself was renamed from "Jakarta Bean Validation" to "Jakarta Validation." The namespace (jakarta.validation.*) and the annotations you already know (@NotBlank, @Size, @Valid, @Constraint) are unchanged -- this is a spec-title change, not an API break.
• The minimum required Java version moved to 17. Not a concern for anything already running JDK 21 or 25, but it is the reason Hibernate Validator 9.x cannot be backported to run on Java 11.
• Record validation is now explicitly specified, closing a real gap in 3.0 where the spec was silent on how a constraint on a record component should behave. That is substantial enough to earn its own chapter -- see below.

Going deeper

• Jakarta Validation news and release history (rel="nofollow")
• Hibernate Validator reference guide (rel="nofollow")
• Next: Record validation