Spring Validation Between Two Date Fields?

Based on the number of times the question is displayed, I conclude that a lot of people still end up here looking for a validator for a date range.

Suppose we have a DTO containing another DTO (or class with @Embeddable annotation) with two fields with LocalDate (or other date representation, it's only example).

class MyDto {

    @ValidDateRange // <-- target annotation
    private DateRange dateRange;
    
    // getters, setters, etc.
}

class DateRange {

    private LocalDate startOfRange;
    private LocalDate endOfRange;

    // getters, setters, etc.
}

Now, we can declare our own @ValidDateRange annotation:

@Documented
@Constraint(validatedBy = DateRangeValidator.class)
@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@interface ValidDateRange {

    String message() default "Start date must be before end date";

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

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

Writing the validator itself also comes down to a few lines of code:

class DateRangeValidator implements ConstraintValidator<ValidDateRange, DateRange> {
    @Override
    public boolean isValid(DateRange value, ConstraintValidatorContext context) {
        return value.getStartOfRange().isBefore(value.getEndOfRange());
    }
}

Reference: https://blog.tericcabrel.com/write-custom-validator-for-body-request-in-spring-boot/

Create DateRange annotation

@Constraint(validatedBy = DateRangeValidator.class)
@Target({ElementType.TYPE, ElementType.FIELD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented

public @interface DateRange {
    String message() default "{mob.concept.admin.models.constraint.DateRange.message}";

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

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

    String before();

    String after();
}

create validator Constraint

public class DateRangeValidator implements ConstraintValidator<DateRange, Object> {
    private String beforeFieldName;
    private String afterFieldName;

    @Override
    public void initialize(DateRange constraintAnnotation) {
        beforeFieldName = constraintAnnotation.before();
        afterFieldName = constraintAnnotation.after();
    }

    @Override
    public boolean isValid(final Object value, ConstraintValidatorContext context) {
        try {
            final Field beforeDateField = value.getClass().getDeclaredField(beforeFieldName);
            beforeDateField.setAccessible(true);

            final Field afterDateField = value.getClass().getDeclaredField(afterFieldName);
            afterDateField.setAccessible(true);

            final LocalDate beforeDate = (LocalDate) beforeDateField.get(value);
            final LocalDate afterDate = (LocalDate) afterDateField.get(value);
            return beforeDate.isEqual(afterDate) || beforeDate.isBefore(afterDate);

        } catch (NoSuchFieldException | IllegalAccessException ignored) {
            return false;
        }
    }
}

Example

@DateRange(before = "startDate", after = "endDate", message = "Start date should be less than end date")
public class OfferDto {
    @NotNull(message = "offer title required")
    @Size(max = 20, min = 8, message = "Offer title must be between 8 and 20 characters")
    private String offerTitle;
    @Size(max = 100, min = 8, message = "Offer title must be between 8 and 100 characters")
    @NotNull(message = "offer description required")
    private String description;
    @NotNull(message = "start date is required")
    private LocalDate startDate;
    @NotNull(message = "end date is required")
    private LocalDate endDate;
    @NotNull(message = "discount is required")
    private Float discount;
    @NotNull(message = "offer type is required")
    @EnumValidation(enumsClass = OfferType.class)
    private String offerType;
}

For sure you can use Bean Validation inside your controller, just add an annotation on the property like you did in your model. But the best way would be use a Date type in your model instead of string.