修改并验证grails域对象而不保存它

class Person {
    String name
    Integer age

    static constraints = {
        name blank: false, maxSize: 50
        age min: 0, max: 120
    }
}

def update(Long id, Long version) {
    def personInstance = Person.get(id)
    if (!personInstance) {
        flash.message = "Person not found with id $id"
        redirect action: 'list'
        return
    }

    if (version != null) {
        if (personInstance.version > version) {
            personInstance.errors.rejectValue('version', 'person.optimistic.locking.failure',
                    [message(code: 'person.optimistic.locking.failure', default: "Another user has updated this Person while you were editing")] as Object[],
                    "Another user has updated this Person while you were editing")
            render view: 'edit', model: [personInstance: personInstance]
            return
        }
    }

    personInstance.properties = params

    if (!personInstance.validate()) {
        render view: 'edit', model: [personInstance: personInstance]
        return
    }

    personInstance.save flush: true

    flash.message = "Person updated successfully"
    redirect action: 'show', id: personInstance.id
}

<g:hasErrors bean="${personInstance}">
    <div class="alert alert-danger">
        <g:renderErrors bean="${personInstance}" as="list" />
    </div>
</g:hasErrors>