JPA入门（二）双向一对多
package org.jzkangta.onetomany;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.JoinColumn;import javax.persistence.ManyToOne;/** * 多的一方为关系维护端，关系维护端是指负责外键的更新 * @author Administrator * */@Entitypublic class OrderItem {@Id@GeneratedValueprivate int id;@Column(length=40,nullable=false)private String name;@Column(nullable=false)private Float price = 0f;@ManyToOne(cascade={CascadeType.MERGE,CascadeType.REFRESH},fetch=FetchType.EAGER,optional=false)//cascade不用为ALL，fetch=FetchType.EAGER为默认，optional=true是指order可以为null@JoinColumn(name="order_id")//外键的字段名字private Order order;public int getId() { return id; }public void setId( int id ) { this.id = id; }public String getName() { return name; }public void setName( String name ) { this.name = name; }public Float getPrice() { return price; }public void setPrice( Float price ) { this.price = price; }public Order getOrder() { return order; }public void setOrder( Order order ) { this.order = order; }}