RESTful Grails:如何在XML中包含相关实体？

grails install-plugin rest
grails install-plugin restful-authentication

class Person {
    String name
    String email
    static constraints = {
        name blank: false
        email blank: false, email: true
    }
}

grails generate-controller Person

class PersonController {
    static allowedMethods = [save: "POST", update: "PUT", delete: "DELETE"]

    def index() {
        render Person.list() as XML
    }

    def show() {
        Person person = Person.get(params.id)
        if (!person) {
            render status: 404
            return
        }
        render person as XML
    }

    def create() {
        Person person = new Person(request.XML)
        if (person.save()) {
            response.status = 201
            render person as XML
        } else {
            render status: 400
        }
    }

    def update() {
        Person person = Person.get(params.id)
        if (!person) {
            render status: 404
            return
        }
        person.properties = request.XML
        if (person.save()) {
            render person as XML
        } else {
            render status: 400
        }
    }

    def delete() {
        Person person = Person.get(params.id)
        if (!person) {
            render status: 404
            return
        }
        person.delete()
        render status: 204
    }
}

class UrlMappings {
    static mappings = {
        "/$controller/$action?/$id?"{
            constraints {
                // apply constraints here
            }
        }
        "/api/people"(resources: "person")
    }
}