JPA实现一对多

JPA实现一对多，以定单和定单项为例

1.Order.java  定单类

package com.cyberwise.jpa.one2many;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

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;
import javax.persistence.Version;

@Entity
@Table(name = "orders")
public class Order implements Serializable {

	@Version
	private Long version;

	@Id
	private String orderId;

	private Float amount = 0f;

	@OneToMany(cascade = { CascadeType.PERSIST, CascadeType.REFRESH,
			CascadeType.REMOVE, CascadeType.MERGE }, fetch = FetchType.LAZY, mappedBy = "order")//这里配了mappedBy，也就是属于双向关联了，既可以从这张表找到另外一张表，也可以从别外的表找到这张表
	private List<OrderItem> items = new ArrayList<OrderItem>();
	
	public Order(){
		
	}

	@Column(name="版本号")
	public Long getVersion() {
		return version;
	}

	public void setVersion(Long version) {
		this.version = version;
	}

	@Column(name="定单号",length = 12)
	public String getOrderId() {
		return orderId;
	}

	public void setOrderId(String orderId) {
		this.orderId = orderId;
	}

	@Column(name="总数",nullable = false)
	public Float getAmount() {
		return amount;
	}

	public void setAmount(Float amount) {
		this.amount = amount;
	}

	public List<OrderItem> getItems() {
		return items;
	}

	public void setItems(List<OrderItem> items) {
		this.items = items;
	}
	
	public void addOrderItem(OrderItem orderItem){
		orderItem.setOrder(this);
		this.items.add(orderItem);
	}

	

	
}

2.OrderItem.java  定单项类

package com.cyberwise.jpa.one2many;

import java.io.Serializable;

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;
import javax.persistence.Table;
import javax.persistence.Version;

@Entity
@Table(name="orderitems")
public class OrderItem implements Serializable{
	
	@Version
	private Long version;
	
	@Id
	@GeneratedValue
	private Integer id;
	
	private String productName;
	
	private Float sellPrice =0f;//默认为0
	
	@ManyToOne(cascade={CascadeType.MERGE,CascadeType.REFRESH},optional=false)
	@JoinColumn(name="order_id")//设置外键的名称
	private Order order;
	
	public OrderItem(){
		
	}

	@Column(name="版本号")
	public Long getVersion() {
		return version;
	}

	public void setVersion(Long version) {
		this.version = version;
	}

	public Integer getId() {
		return id;
	}

	public void setId(Integer id) {
		this.id = id;
	}

	@Column(name="产品名称",length=40,nullable=false)
	public String getProductName() {
		return productName;
	}

	public void setProductName(String productName) {
		this.productName = productName;
	}

	@Column(name="产品价格",nullable=false)
	public Float getSellPrice() {
		return sellPrice;
	}

	public void setSellPrice(Float sellPrice) {
		this.sellPrice = sellPrice;
	}

	public Order getOrder() {
		return order;
	}

	public void setOrder(Order order) {
		this.order = order;
	}

}

3.One2ManyTest.java  测试类

package com.cyberwise.jpa.one2many;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;

import org.jboss.seam.annotations.In;

public class One2ManyTest {
	
	@In
	EntityManagerFactory factory;
	
	@In
	EntityManager manager;
	
	public void save(){
		
		factory = Persistence.createEntityManagerFactory("test");
		manager = factory.createEntityManager();
		manager.getTransaction().begin();
		
		Order order = new Order();
		order.setAmount(200f);
		order.setOrderId("9002");
		
		OrderItem orderItem = new OrderItem();
		orderItem.setProductName("跳绳");
		orderItem.setSellPrice(15f);
		
		OrderItem orderItem2  = new OrderItem();
		orderItem2.setProductName("橄榄球");
		orderItem2.setSellPrice(200f);
		
		order.addOrderItem(orderItem);
		order.addOrderItem(orderItem2);
		
		manager.persist(order);
		manager.getTransaction().commit();
		manager.close();
		factory.close();
	}
	
         /**查看产品*/
	public void query(){
		
		factory = Persistence.createEntityManagerFactory("test");
		manager = factory.createEntityManager();
		
		String sql = "select o from OrderItem o where o.order='9002'";
		List<OrderItem> productList = manager.createQuery(sql).getResultList();
		System.out.println("产品名称：");
		for(OrderItem o : productList){
			System.out.println(o.getProductName());
		}
		
		manager.close();
		factory.close();
		
	}
	
	/**这是修改定单表*/
	public void update(){
		factory = Persistence.createEntityManagerFactory("test");
		manager = factory.createEntityManager();
		manager.getTransaction().begin();
		
		String ql ="update Order o set o.amount =:amount where o.orderId=:orderId";
		Query query = manager.createQuery(ql);
		query.setParameter("amount",100f );
		query.setParameter("orderId", "9002");
		
		query.executeUpdate();
		
		manager.getTransaction().commit();
		manager.close();
		factory.close();
	}
	
	/**修改定单项*/
	public void updateItem(){
		factory = Persistence.createEntityManagerFactory("test");
		manager = factory.createEntityManager();
		manager.getTransaction().begin();
		
		String sql = "update OrderItem o set o.order.orderId =:orderId where o.id=:id";
		Query query = manager.createQuery(sql);
		query.setParameter("orderId", "9001");
		query.setParameter("id", 3);
		query.executeUpdate();
		
		manager.getTransaction().commit();
		manager.close();
		factory.close();
	}
	
	/**增加定单项*/
	public void addProduct(){
		factory = Persistence.createEntityManagerFactory("test");
		manager = factory.createEntityManager();
		manager.getTransaction().begin();
		
		//增加定单号为9002的定单
		String id  = "9002";
		Order order1 = manager.find(Order.class,id);
		OrderItem orderItem = new OrderItem();
		orderItem.setOrder(order1);
		orderItem.setProductName("橄榄球");
		orderItem.setSellPrice(115f);
		
		manager.persist(orderItem);
		manager.getTransaction().commit();
		manager.close();
		factory.close();
	}
	
	public static void main(String[] args) {
		One2ManyTest test = new One2ManyTest();
//		test.save();
		test.query();
//		test.update();
//		test.updateItem();
//		test.addProduct();
	}

}