Hibernate4一对多关系映射

示例：一个类别（Category）下面有多个商品（Product），多个商品对应对应同一类别

 

public class Category {

       private Integer id;
	private String name;
	private Set<Product> products = new HashSet<Product>();

	// getter and setter
}	

 

public class Product {

	private Integer id;
	private String name;
	private Double price;
	private Category category;
	
	// getter and setter
}

用XML映射

<hibernate-mapping package="org.monday.hibernate4.domain">
	<class name="Category" table="tbl_category">
		<id name="id">
			<generator class="identity" />
		</id>
		<property name="name" />
		<set name="products" inverse="true">
			<key column="category_id" />
			<one-to-many class="Product" />
		</set>
	</class>
</hibernate-mapping>

 

<hibernate-mapping package="org.monday.hibernate4.domain">
	<class name="Product" table="tbl_product">
		<id name="id">
			<generator class="identity" />
		</id>
		<property name="name" />
		<property name="price" />
		<many-to-one name="category" class="Category" 
			column="category_id" not-null="true"/>
	</class>
</hibernate-mapping>

 用@Annotation映射

@Entity
@Table(name = "tbl_category")
public class Category {

	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	private Integer id;
	private String name;
        // 使用泛型的话，targetEntity可以不制定
	@OneToMany(mappedBy = "category")
	private Set<Product> products = new HashSet<Product>();

	// getter and setter	
}	

 

@Entity
@Table(name = "tbl_product")
public class Product {

	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	private Integer id;
	private String name;
	private Double price;

	@ManyToOne
	@JoinColumn(name = "category_id", nullable = false)
	private Category category;

	// getter and setter	
}	

 测试代码

Product p = new Product();
p.setName("hibernate");
p.setPrice(99.9);

Category c = new Category();
c.setName("book");
c.getProducts().add(p);

p.setCategory(c);

session.save(c); // 先插入一的一方
session.save(p);

  SQL schema

Hibernate: 
    create table tbl_category (
        id integer not null auto_increment,
        name varchar(255),
        primary key (id)
    )
Hibernate: 
    create table tbl_product (
        id integer not null auto_increment,
        name varchar(255),
        price double precision,
        category_id integer,
        primary key (id)
    )
Hibernate: 
    alter table tbl_product 
        add index FK2BA956E5535EE4C (category_id), 
        add constraint FK2BA956E5535EE4C 
        foreign key (category_id) 
        references tbl_category (id)
Hibernate: 
    insert 
    into
        tbl_category
        (name) 
    values
        (?)
Hibernate: 
    insert 
    into
        tbl_product
        (name, price, category_id) 
    values
        (?, ?, ?)