java - 它如何将一个对象字段数据复制到同一类的另一个对象？

Question

在问题的上下文中，类别表有两行映射到股票。但是当我应用下面的逻辑时，我在结果中只得到一行条目。

为了解决我想知道如何将对象属性复制到同一类的新创建的对象？ 这样新创建的对象将具有旧对象的数据。

public class App {
    public static void main(String[] args) {
        System.out.println("Hibernate many to many (XML Mapping)");
        Session session = HibernateUtil.getSessionFactory().openSession();
        session.beginTransaction();

        try {
            List<Stock> stocksNew=new ArrayList<Stock>();
            List<Stock> stocks = session.createQuery("FROM Stock").list(); 

            for (Stock stock:stocks) {
                Set<Category> categories = stock.getCategories();

                if (categories.isEmpty())
                {
                    System.out.println("true");
                    stocksNew.add(stock);
                } 
                else
                {   
                    for (Iterator<Category> iterator2 = 
                        categories.iterator(); iterator2.hasNext();) {
                        Category category = (Category) iterator2.next();
                        stock.
                        stock.setCategoryId(category.getCategoryId());
                        stock.setName(category.getName());
                        stocksNew.add(stock);

                    }
                }   
            }

            for (Stock stock : stocksNew) {
                System.out.println("Stock ID: " + stock.getStockId()); 
                System.out.println("Stock Name: " + stock.getStockName()); 
                System.out.println("Stock  Code: " + stock.getStockCode()); 
                System.out.println("Category Id:"+stock.getCategoryId());
                System.out.println("Category Name:"+stock.getName());
            }


        } catch (HibernateException e) {
            e.printStackTrace(); 
        } finally {
            session.close(); 
        }
    }

}

输出

Stock ID: 1
Stock Name: PADINI
Stock  Code: 7052
Category Id:2
Category Name:INVESTMENT
Stock ID: 1
Stock Name: PADINI
Stock  Code: 7052
Category Id:2
Category Name:INVESTMENT

我得到了上述输出，但根据我的要求，输出应该以以下方式出现

Stock ID: 1
Stock Name: PADINI
Stock  Code: 7052
Category Id:1
Category Name:CONSUMER
Stock ID: 1
Stock Name: PADINI
Stock  Code: 7052
Category Id:2
Category Name:INVESTMENT

Answer 1

要将属性从一个 Java 对象复制到另一个 Java 对象，我建议您查看 Java bean 映射器，例如 orika或Dozer 。它们可以为您节省大量代码，并且可以很好地自动执行此任务。