Hibernate5更新只收集多对多关系

Question

我用 Hibernate 5.2 映射了下图

这些是我的实体类：

库存

@Entity
@Table(name = "stock", catalog = "mkyongdb", uniqueConstraints = {
        @UniqueConstraint(columnNames = "STOCK_NAME"),
        @UniqueConstraint(columnNames = "STOCK_CODE") })
public class Stock implements java.io.Serializable {

    @Id
    @GeneratedValue(strategy = IDENTITY)
    @Column(name = "STOCK_ID", unique = true, nullable = false)
    private Integer stockId;

    @Column(name = "STOCK_CODE", unique = true, nullable = false, length = 10)
    private String stockCode;

    @Column(name = "STOCK_NAME", unique = true, nullable = false, length = 20)
    private String stockName;

    @ManyToMany(fetch = FetchType.LAZY, cascade = {CascadeType.MERGE, CascadeType.REFRESH})
    @JoinTable(name = "stock_category", catalog = "mkyongdb", joinColumns = {
            @JoinColumn(name = "STOCK_ID", nullable = false, updatable = false) },
            inverseJoinColumns = { @JoinColumn(name = "CATEGORY_ID",
                    nullable = false, updatable = false) })
    private Set<Category> categories = new HashSet<>();

    //Getter and Setter

}

类别

@Entity
@Table(name = "category", catalog = "mkyongdb")
public class Category implements java.io.Serializable {

    @Id
    @GeneratedValue(strategy = IDENTITY)
    @Column(name = "CATEGORY_ID", unique = true, nullable = false)
    private Integer categoryId;

    @Column(name = "NAME", nullable = false, length = 10)
    private String name;

    @Column(name = "[DESC]", nullable = false)
    private String desc;

    @ManyToMany(fetch = FetchType.LAZY, mappedBy = "categories", cascade = {CascadeType.MERGE, CascadeType.REFRESH})
    private Set<Stock> stocks = new HashSet<>();

    //Getter and Setter

}

一切正常。

我需要做的只是将类别列表添加到股票中。我不想修改Stock 实体，只是在stock_category 表中添加或删除类别。

这是我的服务：

@Override
@Transactional(rollbackFor = StockException.class)
public void addCategoriesToStock(Set<Category> categories, Stock stock) throws StockException{
    stock = sessionFactory.getCurrentSession().get(Stock.class, stock.getCodStock());
    stock.setCategories(categories);
    sessionFactory.getCurrentSession().update(stock);
    sessionFactory.getCurrentSession().flush();
}

这是对服务的测试

@Test
public void testAddCategoriesStock() throws Exception {
    Stock newValues = new Stock();
    newValues.setStockId(1);
    Category category = new Category();
    category.setCategoryId(13);
    dao.addCategoriesToStock(new HashSet<>(Arrays.asList(category)), newValues);
    List<Stock> stocks = dao.getAllStockeByCategoriesCriteria(category);
    for (Stock stock : stocks) {
        System.out.println(stock);
    }
}

测试运行良好，没有错误，但是在浏览与类别“13”（getAllStockeByCategoriesCriteria）关联的股票时，它没有给我带来任何股票。那么之前执行的操作就不起作用了。

如何添加或删除类别？

Answer 1

你必须在两边添加依赖，所以你错过了将Stock添加到categories：

@Override
@Transactional(rollbackFor = StockException.class)
public void addCategoriesToStock(List<Category> categories, Stock stock) throws StockException{
    stock = sessionFactory.getCurrentSession().get(Stock.class, stock.getCodStock());
    stock.setCategories(categories);

    for(Category cat: categories){
        cat.getStocks().add(stock);
    }

    sessionFactory.getCurrentSession().merge(stock);
    sessionFactory.getCurrentSession().flush();
}

另外我认为你应该使用merge 而不是update 来使级联工作。

之后，您的代码应该保存关系。

Answer 2

根据第一个响应，这是我在方法中留下的代码。

更改签名，因为我只需要实体的标识符就可以关联它们，并且如 Maciej Kowalski 所示，关系必须保持双向

我还通过 Set 更改了列表，以确保不会重复这些值

这将是我为关系添加类别列表的服务

@Override
@Transactional(rollbackFor = StockException.class)
public void addCategoriesToStock(Set<Integer> categoryCodes, Integer codStock) throws StockException{
    //I get the stock I'm going to associate
    Stock stock = sessionFactory.getCurrentSession().get(Stock.class, codStock);
    if (categoryCodes != null) {
    //For each category to add to the stock, I consult and add the relationship in both entities
        for (Integer codCategory : categoryCodes) {
            Category category = sessionFactory.getCurrentSession().get(Category.class, codCategory);
            category.add(stock);
            stock.add(category);
        }
    }
    sessionFactory.getCurrentSession().merge(stock);
    sessionFactory.getCurrentSession().flush();
}

这将是从关系中删除类别列表的服务

@Override
@Transactional(rollbackFor = StockException.class)
public void removeCategoriesToStock(Set<Integer> categoryCodes, Integer codStock) throws StockException{
    //I get the stock that I will disassociate
    Stock stock = sessionFactory.getCurrentSession().get(Stock.class, codStock);
    if (categoryCodes != null) {
    //For each category to eliminate the stock, I consult and eliminate the relationship in both entities
        for (Integer codCategory : categoryCodes) {
            Category category = sessionFactory.getCurrentSession().get(Category.class, codCategory);
            category.remove(stock);
            stock.remove(category);
        }
    }
    sessionFactory.getCurrentSession().merge(stock);
    sessionFactory.getCurrentSession().flush();
}

我的疑问是，在建立两个实体之间的关系之前，我必须在数据库中查询它们以获取对象并对其进行操作。因此，我必须为要关联的每个标识符都这样做，我想应该存在性能问题。

但是暂时我会留下它，以防我找到更优化的方法在这里发布它