Using GORM for MongoDB in Spring Boot

boot-gorm-mongodb.groovy

@Grab("org.grails:gorm-mongodb-spring-boot:1.0.0.RC1")
import grails.persistence.*
import grails.mongodb.geo.*
import org.bson.types.ObjectId
import com.mongodb.BasicDBObject
import org.springframework.http.*
import org.springframework.beans.factory.annotation.Autowired
import static org.springframework.web.bind.annotation.RequestMethod.*

@RestController
class CityController {

    @RequestMapping(value="/", method = GET)
    List index() {
        City.list().collect { [name: it.name] }
    }

    @RequestMapping(value="/near/{cityName}", method = GET)
    ResponseEntity near(@PathVariable String cityName) {
        def city = City.where { name == cityName }.find()
        if(city) {
            List<City> closest = City.findAllByLocationNear(city.location)
            return new ResponseEntity([name: closest[1].name], HttpStatus.OK)
        }
        else {
            return new ResponseEntity(HttpStatus.NOT_FOUND)
        }
    }

    @PostConstruct
    void populateCities() {
        City.withTransaction{
            City.collection.remove(new BasicDBObject())
            City.saveAll( [ new City(name:"London", location: Point.valueOf( [-0.125487, 51.508515] ) ),
                            new City(name:"Paris", location: Point.valueOf( [2.352222, 48.856614] ) ),
                            new City(name:"New York", location: Point.valueOf( [-74.005973, 40.714353] ) ),
                            new City(name:"San Francisco", location: Point.valueOf( [-122.419416, 37.774929] ) ) ] )
        }
    }
}

@Entity
class City {
    ObjectId id
    String name
    Point location

    static constraints = {
        name blank:false
        location nullable:false
    }

    static mapping = {
        location geoIndex:'2dsphere'
    }
}

Is there any way to customize the constraint validation error message? If so, how? And if we can customize the constraint validation message like in Grails, would you recommend Spring Boot over Grails if application is being used as a RESTful service?