Built-in Validation Rules - rulii Documentation

rulii ships with 39+ ready-to-use validation rules. Each one checks a specific constraint and adds a RuleViolation when the check fails.

Available Validation Rules

Rule	What It Checks
NotNullValidationRule	Value is not null
NotEmptyValidationRule	String/Collection is not empty
NotBlankValidationRule	String is not blank (not null, not empty, not whitespace)
SizeValidationRule	String/Collection size is within range
MinValidationRule	Number ≥ minimum
MaxValidationRule	Number ≤ maximum
DecimalMinValidationRule	Decimal ≥ minimum
DecimalMaxValidationRule	Decimal ≤ maximum
EmailValidationRule	Valid email format
UrlValidationRule	Valid URL format
PatternValidationRule	Matches a regex pattern
AssertTrueValidationRule	Value is true
AssertFalseValidationRule	Value is false
PositiveValidationRule	Number > 0
PositiveOrZeroValidationRule	Number ≥ 0
NegativeValidationRule	Number < 0
NegativeOrZeroValidationRule	Number ≤ 0
FutureValidationRule	Date is in the future
FutureOrPresentValidationRule	Date is now or in the future
PastValidationRule	Date is in the past
PastOrPresentValidationRule	Date is now or in the past
DigitsValidationRule	Number has expected integer/fraction digits
LowerCaseValidationRule	String is all lowercase
UpperCaseValidationRule	String is all uppercase
AlphaValidationRule	String contains only letters
AlphaNumericValidationRule	String contains only letters and digits
NumericValidationRule	String contains only digits
StartsWithValidationRule	String starts with a prefix
EndsWithValidationRule	String ends with a suffix
ContainsValidationRule	String contains a substring

Basic Usage

// Create a validation rule for a field called "name"
NotNullValidationRule notNull = new NotNullValidationRule("name");

// Wrap it as a Rule
Rule rule = Rule.builder().build(notNull);

// Run it
RuleViolations violations = new RuleViolations();
rule.run(name -> null, ruleViolations -> violations);

// Check for errors
violations.hasErrors(); // true — name was null

Collecting Violations

Validation rules automatically add violations to the ruleViolations binding. Pass a RuleViolations instance to collect errors:

RuleSet<?> ruleSet = RuleSet.builder()
    .with("FormValidation")
    .rule(Rule.builder().build(new NotNullValidationRule("name")))
    .rule(Rule.builder().build(new SizeValidationRule("name", 2, 50)))
    .rule(Rule.builder().build(new EmailValidationRule("email")))
    .build();

RuleViolations violations = new RuleViolations();

ruleSet.run(
    name -> "",
    email -> "not-valid",
    ruleViolations -> violations
);

for (RuleViolation v : violations) {
    System.out.println(v.getErrorMessage());
}

Customizing Error Details

// Custom error code and severity
NotNullValidationRule rule = new NotNullValidationRule(
    "name",               // field name
    "ERR-001",            // error code
    Severity.FATAL,       // severity level
    "Name is required!"  // custom message
);