# 2. Record validation, field-level and class-level

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Source: [`ContactFormRecord.java`](../src/main/java/com/ankurm/customvalidation/dto/ContactFormRecord.java),
[`EventBookingRecord.java`](../src/main/java/com/ankurm/customvalidation/dto/EventBookingRecord.java),
[`DateRangeValid.java`](../src/main/java/com/ankurm/customvalidation/validator/DateRangeValid.java).
Test: [`ValidationScenariosTest.java`](../src/test/java/com/ankurm/customvalidation/ValidationScenariosTest.java).
Transcripts: [`docs/output/03-record-based-spam-rejected.txt`](output/03-record-based-spam-rejected.txt),
[`docs/output/05-record-based-bad-date-range.txt`](output/05-record-based-bad-date-range.txt),
[`docs/output/06-record-based-good-date-range.txt`](output/06-record-based-good-date-range.txt).

## Field-level: a constraint on a record component

`ContactFormRecord` carries the same three constraints as the class-based `ContactForm` --
`@NotBlank`, `@Email`, `@SpamMessageCheck` -- placed directly on record components instead of
fields:

```java
public record ContactFormRecord(
        @NotBlank(message = "Email cannot be empty!")
        @Email(message = "Please provide a valid email address.")
        String email,

        @NotBlank(message = "Message cannot be empty!")
        @Size(min = 10, message = "Message must be at least 10 characters long.")
        @SpamMessageCheck
        String message
) {
}
```

This only compiles because `@SpamMessageCheck`'s `@Target` includes `RECORD_COMPONENT` (see
[`SpamMessageCheck.java`](../src/main/java/com/ankurm/customvalidation/validator/SpamMessageCheck.java)).
Forget that element type on a custom constraint and the annotation still compiles fine on a class
field -- it simply cannot be placed on a record component at all, a compile error rather than a
silent no-op. Built-in constraints like `@NotBlank` already declare `RECORD_COMPONENT`, which is
why they worked on a hand-rolled record before this module ever touched the topic; a homemade
constraint needs the same declaration deliberately added.

Rejection behaves identically to the class-based version at the validation layer -- same
constraint, same message:

```
POST /contact-record
{"email":"spammy@email.com","message":"This is spam."}
```

[`docs/output/03-record-based-spam-rejected.txt`](output/03-record-based-spam-rejected.txt) shows
the one thing that is *not* identical: the HTTP response body. See
[the next chapter](03-what-the-defaults-do-not-do.md) for why.

## Class-level (cross-field): a constraint on the record's type

`EventBookingRecord` carries `@DateRangeValid` on the record's type declaration -- the same
position a class-level constraint occupies on an ordinary class:

```java
@DateRangeValid
public record EventBookingRecord(
        @NotNull(message = "startDate is required") LocalDate startDate,
        @NotNull(message = "endDate is required") LocalDate endDate
) {
}
```

The one code change a cross-field validator needs to support both shapes is in the validator
itself, not the annotation -- [`DateRangeValidator`](../src/main/java/com/ankurm/customvalidation/validator/DateRangeValidator.java)
dispatches on the runtime type and reads accessor methods that differ by naming convention only:

```java
if (value instanceof EventBooking booking) {
    return booking.getEndDate().isAfter(booking.getStartDate());
}
if (value instanceof EventBookingRecord booking) {
    return booking.endDate().isAfter(booking.startDate());  // record accessors, no "get" prefix
}
```

Both shapes reject the same bad input the same way:

```
POST /booking-record
{"startDate":"2026-05-10","endDate":"2026-05-01"}
```

HTTP 400 -- [`docs/output/05-record-based-bad-date-range.txt`](output/05-record-based-bad-date-range.txt) --
and a correctly-ordered pair is accepted:
[`docs/output/06-record-based-good-date-range.txt`](output/06-record-based-good-date-range.txt).

## Going deeper

- Records themselves: [Java Records (JEP 395)](https://openjdk.org/jeps/395) (rel="nofollow")
- Prev: [The jakarta.validation namespace](01-jakarta-namespace-and-bean-validation-3-1.md)
- Next: [What the defaults do not do](03-what-the-defaults-do-not-do.md)