Spring-boot读书笔记一javax.validation.Validation

javax.validation.Validation is the entry point class for the Bean Validation API (JSR-303/JSR-380). It provides factory methods to create validator instances.

Purpose:

• Creates ValidatorFactory and Validator instances
• Bootstrap the validation framework
• Configure validation providers (like Hibernate Validator)

Key Methods:
1. buildDefaultValidatorFactory()

ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
Validator validator = factory.getValidator();

• Creates factory with default configuration
• Uses default validation provider (usually Hibernate Validator)

2. byDefaultProvider()

Validator validator = Validation.byDefaultProvider()
    .configure()
    .buildValidatorFactory()
    .getValidator();

• More control over configuration
• Can customize validation behavior

Common Usage Pattern:

// Get validator instance
Validator validator = Validation.buildDefaultValidatorFactory().getValidator();

// Validate an object
Set<ConstraintViolation<User>> violations = validator.validate(user);

// Check results
if (violations.isEmpty()) {
    // Valid object
} else {
    // Handle violations
    violations.forEach(v -> System.out.println(v.getMessage()));
}

What it validates:

• Fields annotated with @NotNull, @Size, @Email, etc.
• Custom constraints like your @Password annotation
• Nested object validation with @Valid

Dependencies:

• Requires Bean Validation implementation (Hibernate Validator)
• Provided by spring-boot-starter-validation

The Validation class is the standard way to programmatically validate objects in Java.