我如何使用hibernate方法插入一行

Question

我正在尝试将一行插入到关系表Stock Category.

我遵循这个例子:http://www.mkyong.com/hibernate/hibernate-many-to-many-example-join-table-extra-column-annotation/

现在我已经有了表stock和category中的数据。

稍后我想将股票和类别相互关联。

我怎么能做到这一点，而不写一个自定义sql查询?

如果我可以像这样添加StockCategory是可能的吗?

Stock stock = new Stock();
stock.setStockId(1);
Category category = new Category();
category.setCategoryId(1);
StockCategory stockCategory = new StockCategory();
stockCategory.setStock(stock); //here you need to get the stock object by id 
stockCategory.setCategory(category1); //here you need to get the category1 object by id
stockCategory.setCreatedDate(new Date()); //extra column
stockCategory.setCreatedBy("system"); //extra column
session.save(stockCategory );

Answer 1

StockCategory stockCategory = new StockCategory();
stockCategory.setStock(stock); //here you need to get the stock object by id
stockCategory.setCategory(category1); //here you need to get the category1 object by id
stockCategory.setCreatedDate(new Date()); //extra column
stockCategory.setCreatedBy("system"); //extra column
session.save(stock);

Answer 2

像Hibernate这样的ORM将Java对象映射到数据源并创建该数据的模型，然后创建和更新对象并调用save子例程来更新模型。SQL的Insert/Update/Delete命令由ORM库完成。

因此，在创建新对象的示例中，直到调用session.save(stock)才更新数据源。

   session.beginTransaction();
    Stock stock = new Stock();
    stock.setStockCode("7052");
    stock.setStockName("PADINI");
    //assume category id is 7
    Category category1 = (Category)session.get(Category.class, 7);
    StockCategory stockCategory = new StockCategory();
    stockCategory.setStock(stock);
    stockCategory.setCategory(category1);
    stockCategory.setCreatedDate(new Date()); //extra column
    stockCategory.setCreatedBy("system"); //extra column
    stock.getStockCategories().add(stockCategory);
    session.save(stock);
    session.getTransaction().commit();

Answer 3

只要您定义了适当的关系，您的代码就可以工作。例如，如果您的StockCategory.java看起来像这样，那么您所做的将会工作。

Class StockCategory{
     @ManyToOne(...)
     private Stock stock;
     @ManyToOne(...)
     private Category category;
}

那么下面的代码将工作。您不必在Stock和Category中填充其他字段。

    Stock stock = new Stock();
    stock.setStockId(1);
    Category category = new Category();
    category.setCategoryId(1);
    StockCategory stockCategory = new StockCategory();
    stockCategory.setStock(stock); 
    stockCategory.setCategory(category1); 
    stockCategory.setCreatedDate(new Date()); //extra column
    stockCategory.setCreatedBy("system"); //extra column
    session.save(stockCategory );