I. Background

Recently, while using javax.validation for validation, I found there was no annotation for validating BigDecimal types, so I created one myself.

II. Define Annotation and Validator Class

2.1 Annotation Class

@Documented
@Constraint(validatedBy = BigDecimalRangeValidator.class)
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface BigDecimalRange {
    double min() default Double.MIN_VALUE;

    double max() default Double.MAX_VALUE;

    String message() default "Validation failed";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};
}

2.2 Validator Class

public class BigDecimalRangeValidator implements ConstraintValidator<BigDecimalRange, BigDecimal> {

    private BigDecimal minValue;
    private BigDecimal maxValue;

    @Override
    public void initialize(BigDecimalRange constraintAnnotation) {
        minValue = new BigDecimal(constraintAnnotation.min());
        maxValue = new BigDecimal(constraintAnnotation.max());
    }

    @Override
    public boolean isValid(BigDecimal value, ConstraintValidatorContext constraintValidatorContext) {
        if (value == null) {
            return true;
        }
        return value.compareTo(minValue) >= 0 && value.compareTo(maxValue) <= 0;
    }
}

III. Using the Annotation

public class Example {

    /**
     * Test field
     */
    @BigDecimalRange(min = 0.1, max = 9.9, message = "The range of the test field is 0.1~9.9")
    private BigDecimal testValue;
}