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
? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 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); } }
OrderItem.java代码
? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 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; } }
3.测试代码
? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 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(); } }
4.配置文件persistence.xml和前面JPA（一）、、、一样，在此省略
