Java validation framework

Simple and extensible validator pattern implementation with sensible defaults

Why?

How many times You had to implement Validator Pattern? Or maybe how many times You wish you did? This java library provides some easy and extensible interfaces to introduce consistent way of validation through your application.

Usage

Add library dependency:

compile "com.github.bgalek.utils:validation-framework:1.0.0"

Let's assume a very simple class to validate:

public class MovieCharacter {
    public final String value;
}

Use provided implementations:

DefaultValidator

Validations are processed respecting declaration order. Will return a PositiveValidationResult only when all validations are successful, otherwise, it stops at first fail encountered and returns: NegativeValidationResult

Validator<MovieCharacter> characterValidator = Validator.of(MovieCharacter.class)
        .validation(movieStar -> movieStar.value.length() > 0, "name needs to has to be at least 1 character long")
        .validation(movieStar -> Character.isUpperCase(movieStar.value.charAt(0)), "name needs to start with uppercase letter")
        .validation(movieStar -> movieStar.value.length() < 50, "name needs to has to be shorter than 50 characters")
        .ensure();

DefaultValidator with exception instead of validation result

Validations are processed respecting declaration order. Will return a PositiveValidationResult only when all validations are successful, otherwise, it stops at first fail encountered and throws provided exception.

Validator<MovieCharacter> characterValidator = Validator.of(MovieCharacter.class)
        .validation(movieStar -> movieStar.value.length() > 0, "name needs to has to be at least 1 character long")
        .validation(movieStar -> Character.isUpperCase(movieStar.value.charAt(0)), "name needs to start with uppercase letter")
        .validation(movieStar -> movieStar.value.length() < 50, "name needs to has to be shorter than 50 characters")
        .ensure(IllegalArgumentException::new);

SummaryValidator

Validations are processed respecting declaration order. Will return a ValidationSummary containing passed and failed validations.

SummaryValidator<MovieCharacter> characterValidator = Validator.of(MovieCharacter.class)
        .validation(movieStar -> movieStar.value.startsWith("A"), "only names starting with A allowed")
        .validation(movieStar -> movieStar.value.split(" ").length == 2, "has to contain name and surname")
        .validation(movieStar -> movieStar.value.endsWith("Z"), "only names ending with Z allowed")
        .summary();

Extending

You can implement your own validators

class SystemOutValidator<T> implements Validator<T> {

        private final Map<Predicate<T>, String> validations;

        public SystemOutValidator(Map<Predicate<T>, String> validations) {
            this.validations = validations;
        }

        @Override
        public ValidationResult<T> validate(T subject) {
            validations.forEach((key, value) -> System.out.println("processing: " + value));
            return new PositiveValidationResult<>(subject, new HashSet<>(validations.values()));
        }
    }

and use them like this:

Validator<MovieCharacter> customValidator = Validator.of(MovieCharacter.class, SystemOutValidator::new)
        .validation(movieStar -> movieStar.value.length() > 0, "name needs to has to be at least 1 character long")
        .validation(movieStar -> movieStar.value.length() < 50, "name needs to has to be shorter than 50 characters")
        .ensure();

Check out unit tests for more examples!