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在问题的上下文中，Category 表有两行映射到 Stock。但是当我应用下面的逻辑时，我只得到一个行条目。

为了解决这个问题，我想知道如何将对象属性复制到同一类的新创建对象？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，但在我的要求中，输出应该以休闲方式出现

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
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3 回答 3

1

For copying properties from one Java object to another I'd advise you to have a look at Java bean mappers like orika or Dozer. They can save you a lot of code and can automate this task pretty well.

于 2013-10-19T17:35:43.967 回答
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In the logic code, I see that you try to get Categories from Stocks: 

Set<Category> categories = stock.getCategories();

after that you also set Categories to Stocks:

stock.setCategoryId(category.getCategoryId());

==> You'd better re-design your application.

Regarding this your question:

To solve that i want to know how to copy an object properties to newly created object of the same class? So that newly created object will have the data of older object.

Java lang Object has a method java.lang.Object.clone(), which may help.

于 2013-10-19T17:34:12.560 回答
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如果您只想将一个对象的属性复制到另一个对象，则可以使用 java.lang 包中可用的 java 的 object.clone 方法...它将所有属性复制到新实例化的对象...

于 2013-10-19T17:32:17.157 回答