Annotation based validations that work both on client- and server-side.
Java JavaScript
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Build Status Code Climate

validum is a basic lib that adds validations to your classes that can be called via annotations. It uses Java 8 brand new feature, the annotation target option ElementType.TYPE_USE, that allows you to validate the contents of your arrays and Lists with fine control.


  • Full support for both inheritance and composition, how many levels desired;
  • Fine control of arrays' components or lists' elements with Java 8's TYPE_USE target option;
  • Support for custom validations, just create your own annotation and annotate it with @Validator annotation, and then add a custom Validator for it;
  • Class level validations; that is, the annotations can be added to the class declaration, to validate the class's object as a whole;
  • Each annotation must specify the types to which it applies, and exceptions are thrown if they are missused.

Planned Features

  • Javascript client side validation: you will be able to generate a JSON with validation information from your classes, so that a to-be client side library can validate your forms on the browser as well: client and server validations, unified at least.
  • Custom annotation preprocessor for validating each annotation appliable types


  • Simple validations
public class Person {

    private @Required String name;

    private @Natural int age;
  • Validate arrays and lists, using custom annotation @Super
public class SuperHero {

    private @Required @Array(minLength = 2) List<@Required @Super Power> powers;

    private @CharOnly({'x', 'o'}) char @Array.Fixed(3) [] @Array.Fixed(3) [] currentTickTackToeBoard;

Currently Implemented Annotations

Custom annotations can be easily created, but some pre-defined default ones might come in hand. Currently, they are:

  • @Required
  • @Numeric(min, minCap, max, maxCap, type)
  • @Numeric.Max(value)
  • @Numeric.Min(value)
  • @Numeric.Natural
  • @EnumOnly(value)
  • @EnumExcept(value)
  • @Array(minLength, maxLength)
  • @Array.Length(value)