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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package
com.sinoi.bean;
import
java.util.HashSet;
import
java.util.Set;
import
javax.persistence.CascadeType;
import
javax.persistence.Column;
import
javax.persistence.Entity;
import
javax.persistence.FetchType;
import
javax.persistence.GeneratedValue;
import
javax.persistence.Id;
import
javax.persistence.OneToMany;
import
javax.persistence.Table;
@Entity
@Table(name="my_order")
public
class
Order {
@Id
@Column(length=12)
private
String orderId;
@Column(nullable=false)
private
Float amount = 0f;
@OneToMany(cascade={CascadeType.REMOVE, CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH},
mappedBy="order")
private
Set<OrderItem> orderItems = new
HashSet<OrderItem>();
public
String getOrderId() {
return
orderId;
}
public
void
setOrderId(String orderId) {
this.orderId = orderId;
}
public
Float getAmount() {
return
amount;
}
public
void
setAmount(Float amount) {
this.amount = amount;
}
public
Set<OrderItem> getOrderItems() {
return
orderItems;
}
public
void
setOrderItems(Set<OrderItem> orderItems) {
this.orderItems = orderItems;
}
public
void
addOrderItem(OrderItem orderItem) {
orderItem.setOrder(this);//这句代码不加也可！
this.orderItems.add(orderItem);
}
}
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OrderItem.java代码
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package
com.sinoi.bean;
import
javax.persistence.CascadeType;
import
javax.persistence.Column;
import
javax.persistence.Entity;
import
javax.persistence.GeneratedValue;
import
javax.persistence.Id;
import
javax.persistence.JoinColumn;
import
javax.persistence.ManyToOne;
@Entity
public
class
OrderItem {
@Id
@GeneratedValue
private
Integer id;
@Column(length=20, nullable=false)
private
String productName;
@Column(nullable=false)
private
Float sellPrice;
@ManyToOne(cascade={CascadeType.REFRESH, CascadeType.MERGE}, optional=false)
@JoinColumn(name="item_order_for")
private
Order order;
public
Order getOrder() {
return
order;
}
public
void
setOrder(Order order) {
this.order = order;
}
public
Integer getId() {
return
id;
}
public
void
setId(Integer id) {
this.id = id;
}
public
String getProductName() {
return
productName;
}
public
void
setProductName(String productName) {
this.productName = productName;
}
public
Float getSellPrice() {
return
sellPrice;
}
public
void
setSellPrice(Float sellPrice) {
this.sellPrice = sellPrice;
}
}
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3.测试代码
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package
junit.test;
import
javax.persistence.EntityManager;
import
javax.persistence.EntityManagerFactory;
import
javax.persistence.Persistence;
import
org.junit.Test;
import
com.sinoi.bean.Order;
import
com.sinoi.bean.OrderItem;
public
class
UnitTest {
@Test
public
void
save() {
EntityManagerFactory entityManagerFactory = Persistence
.createEntityManagerFactory("unitname");
EntityManager entityManager = entityManagerFactory
.createEntityManager();
entityManager.getTransaction().begin();
Order order = new
Order();
order.setOrderId("jfdkf323");
order.setAmount(232f);
OrderItem orderItem = new
OrderItem();
orderItem.setProductName("basketball");
orderItem.setSellPrice(221f);
OrderItem orderItem2 = new
OrderItem();
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();
}
}
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4.配置文件persistence.xml和前面JPA（一）、、、一样，在此省略
