为何SpringBoot应用中@Valid无需EL依赖，手动构建Validation工厂却需要？

Great question! This difference comes down to how validation is handled in a managed application context versus a standalone, manual setup. Let me break it down clearly:

1. Your application (e.g., Spring Boot) already includes EL dependencies implicitly #

When you use @Valid in a Spring-based app (especially Spring Boot), the framework's starter dependencies take care of pulling in all required components behind the scenes. For example:

• The spring-boot-starter-validation starter automatically includes Hibernate Validator (the default Bean Validation implementation) and transitively pulls in an EL implementation (like GlassFish's javax.el) because Hibernate Validator relies on EL for message interpolation.
• You don't see this dependency in your pom.xml or build.gradle because it's a transitive dependency from the starter—it’s already on your classpath without you adding it explicitly.

2. Manual ValidatorFactory setup uses raw Hibernate Validator logic #

When you call Validation.buildDefaultValidatorFactory() directly, you’re bypassing the application framework’s managed context and using Hibernate Validator’s native core. Hibernate Validator requires an EL ExpressionFactory to process dynamic placeholders in validation messages (like {validatedValue} or {size}) and interpolate values into error messages. If no EL implementation exists on the classpath, it can’t initialize this component, hence the HV000183 error.

3. Managed validation in apps uses framework-adapted components #

In your application, the @Valid annotation is processed by Spring’s LocalValidatorFactoryBean, which integrates seamlessly with the app’s existing environment. This bean either uses the EL implementation already provided by the starter or leverages Spring’s own EL infrastructure, so you never hit the missing dependency issue.

Bonus: Avoid adding the EL dependency (alternative approach) #

If you don’t want to add the javax.el dependency for your manual setup, you can use the ParameterMessageInterpolator as suggested in the error message. This interpolator doesn’t rely on EL and handles basic parameter replacement:

ValidatorFactory factory = Validation.byDefaultProvider()
    .configure()
    .messageInterpolator(new ParameterMessageInterpolator())
    .buildValidatorFactory();

内容的提问来源于stack exchange，提问作者Kyser Soze