Hibernate4之多对多单向关联

多个商品可以在不同的订单中出现，所以商品相对于订单是多对多关系，多对多关系需要新建一个关系表来维护他们之间的关系。
在这里多对多关系@ManyToMany，默认是延迟加载的。级联操作默认只会关联到中间表的修改和删除。

/**
 * @author Chou
 * @since 2012-8-8
 * ...订单实体
 *
 */

@Entity
@Table(name = "TAB_ORDER")
@SequenceGenerator(name = "seq", sequenceName = "SEQ_ORDER", allocationSize = 1)
public class Order {
	private Long id;
	private String orderno;
	private Double money;
	private Set<Item> items = new HashSet<Item>();
	
	@Id
	@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "seq")
	public Long getId() {
		return id;
	}

	......
	
	
	@ManyToMany(fetch = FetchType.EAGER)
	@JoinTable(
			name = "TAB_ORDER_ITEM",
			joinColumns = {@JoinColumn(name = "ORDERID", nullable = false) },
			inverseJoinColumns = {@JoinColumn(name = "ITEMID", nullable = false)}
	)
	public Set<Item> getItems() {
		return items;
	}
	public void setItems(Set<Item> items) {
		this.items = items;
	}
}

/**
 * @author Chou
 * @since 2012-8-8
 * ...商品实体多关联
 *
 */

@Entity
@Table(name = "TAB_ITEM")
@SequenceGenerator(name = "seq", sequenceName = "SEQ_ITEM", allocationSize = 1)
public class Item {
	private Long id;
	private String itemNo;
	private String itemName;
	
	@Id
	@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "seq")
	public Long getId() {
		return id;
	}
	
	......
	
}