如何使用ActiveAndroid加载整个对象（带列表）

我有一个简单的模型：

@Table(name = "Books")
public class Book extends Model {

    @Column(name = "title")
    String title;    

    //Variable to cache the pages
    List<Page> pages;

    public Book(){

    }

    public List<Page> getPages() {
        if (pages==null) pages=getMany(Page.class, "book");
        return pages;
    }
}

我遇到的问题是，我想将整个book对象（及其所有子对象）序列化为JSon（使用GSon），在检索对象时，这些对象没有加载

public String toJSon(long id){
    Book b = new Select().from(Book.class).where("id = ?", id).executeSingle();
    // At this point, the array of pages is obviously empty, and I don't want to hard-call "getPages" because in the future every page will have words, and I would then have to iterate every page, etc..
    Gson gson = new GsonBuilder().create();
    return gson.toJson(b);
}

如何一次加载Book对象及其所有页面

public String toJSon(long id){
    Book b = new Select().from(Book.class).where("id = ?", id).executeSingle();
    // At this point, the array of pages is obviously empty, and I don't want to hard-call "getPages" because in the future every page will have words, and I would then have to iterate every page, etc..
    Gson gson = new GsonBuilder().create();
    return gson.toJson(b);
}