JPA（三）之实体关系一对多（多对一）

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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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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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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();

    }

}