1.背景介绍：
对于购买商品时，订单信息（Order）和订单商品信息（OrderItem）的关系就是一对多的关系。
2.实体bean：
Order.java代码
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packagecom.sinoi.bean;
importjava.util.HashSet;
importjava.util.Set;
importjavax.persistence.CascadeType;
importjavax.persistence.Column;
importjavax.persistence.Entity;
importjavax.persistence.FetchType;
importjavax.persistence.GeneratedValue;
importjavax.persistence.Id;
importjavax.persistence.OneToMany;
importjavax.persistence.Table;
@Entity@Table(name="my_order")
publicclassOrder {
@Id@Column(length=12)
privateString orderId;
@Column(nullable=false)
privateFloat amount = 0f;
@OneToMany(cascade={CascadeType.REMOVE,
mappedBy="order")
privateSet<OrderItem> orderItems =new publicString getOrderId() {
returnorderId;
}
publicvoidsetOrderId(String orderId) {
this.orderId
}
publicFloat getAmount() {
returnamount;
}
publicvoidsetAmount(Float amount) {
this.amount
}
publicSet<OrderItem> getOrderItems() {
returnorderItems;
}
publicvoidsetOrderItems(Set<OrderItem> orderItems) {
this.orderItems
}
publicvoidaddOrderItem(OrderItem orderItem) {
orderItem.setOrder(this);//这句代码不加也可！
this.orderItems.add(orderItem);
}
} |
OrderItem.java代码
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packagecom.sinoi.bean;
importjavax.persistence.CascadeType;
importjavax.persistence.Column;
importjavax.persistence.Entity;
importjavax.persistence.GeneratedValue;
importjavax.persistence.Id;
importjavax.persistence.JoinColumn;
importjavax.persistence.ManyToOne;
@EntitypublicclassOrderItem {
@Id@GeneratedValue
privateInteger id;
@Column(length=20,false)
privateString productName;
@Column(nullable=false)
privateFloat sellPrice;
@ManyToOne(cascade={CascadeType.REFRESH,false)
@JoinColumn(name="item_order_for")
privateOrder order;
publicOrder getOrder() {
returnorder;
}
publicvoidsetOrder(Order order) {
this.order
}
publicInteger getId() {
returnid;
}
publicvoidsetId(Integer id) {
this.id
}
publicString getProductName() {
returnproductName;
}
publicvoidsetProductName(String productName) {
this.productName
}
publicFloat getSellPrice() {
returnsellPrice;
}
publicvoidsetSellPrice(Float sellPrice) {
this.sellPrice
}
} |
3.测试代码
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packagejunit.test;
importjavax.persistence.EntityManager;
importjavax.persistence.EntityManagerFactory;
importjavax.persistence.Persistence;
importorg.junit.Test;
importcom.sinoi.bean.Order;
importcom.sinoi.bean.OrderItem;
publicclassUnitTest {
@Test
publicvoidsave() {
EntityManagerFactory entityManagerFactory
.createEntityManagerFactory("unitname");
EntityManager entityManager = entityManagerFactory
.createEntityManager();
entityManager.getTransaction().begin();
Order order =new order.setOrderId("jfdkf323");
order.setAmount(232f);
OrderItem orderItem =new orderItem.setProductName("basketball");
orderItem.setSellPrice(221f);
OrderItem orderItem2 =new orderItem2.setProductName("football");
orderItem2.setSellPrice(11f);
orderItem.setOrder(order);
orderItem2.setOrder(order);
order.addOrderItem(orderItem);
order.addOrderItem(orderItem2);
entityManager.persist(order);
entityManager.getTransaction().commit();
entityManager.close();
entityManagerFactory.close();
}
} |
4.配置文件persistence.xml和前面JPA（一）、、、一样，在此省略