Using GORM for Hibernate 4 in Spring Boot

boot-gorm-hibernate4.groovy

@Grab("org.grails:gorm-hibernate4-spring-boot:1.0.0.RC2")
@Grab("com.h2database:h2:1.3.173")
import grails.persistence.*
import org.springframework.http.*
import static org.springframework.web.bind.annotation.RequestMethod.*

@RestController
class GreetingController {

    @RequestMapping(value="/person/greet", method = GET)
    String greet(String firstName) {
        def p = Person.findByFirstName(firstName)
        return p ? "Hello ${p.firstName}!" : "Person not found"
    }

    @RequestMapping(value = '/person/add', method = POST)
    ResponseEntity addPerson(String firstName) {
        Person.withTransaction {
            def p = new Person(firstName: firstName).save()
            return new ResponseEntity( p ? HttpStatus.CREATED : HttpStatus.BAD_REQUEST)
        }
    }
}

@Entity
class Person {
    String firstName
}

Hi Graeme!
Call me dumb, but should ResponseEntity, HttpStatus be with[In]Transaction?