jpa onetomany

2019-11-17 03:55:26

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package com.hujuan.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.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
@Entity
@Table(name="orders")
public class Order {

    private String id;
    private Float amount;
    private Set<OrderItem> items = new HashSet<OrderItem>();

    @Id @Column(length=10)
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    @Column(nullable=false)
    public Float getAmount() {
        return amount;
    }
    public void setAmount(Float amount) {
        this.amount = amount;
    }
    //级联操作
    @OneToMany(cascade= {CascadeType.REFRESH,CascadeType.PERSIST,CascadeType.MERGE,CascadeType.REMOVE},fetch=FetchType.LAZY,mappedBy="order")
    public Set<OrderItem> getItems() {
        return items;
    }
    public void setItems(Set<OrderItem> items) {
        this.items = items;
    }

    public void addOrderItem(OrderItem orderItem){
        orderItem.setOrder(this);
        this.items.add(orderItem);
    }
}
package com.hujuan.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.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
@Entity
@Table(name="orders")
public class Order {

    private String id;
    private Float amount;
    private Set<OrderItem> items = new HashSet<OrderItem>();

    @Id @Column(length=10)
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    @Column(nullable=false)
    public Float getAmount() {
        return amount;
    }
    public void setAmount(Float amount) {
        this.amount = amount;
    }
    //级联操作
    @OneToMany(cascade= {CascadeType.REFRESH,CascadeType.PERSIST,CascadeType.MERGE,CascadeType.REMOVE},fetch=FetchType.LAZY,mappedBy="order")
    public Set<OrderItem> getItems() {
        return items;
    }
    public void setItems(Set<OrderItem> items) {
        this.items = items;
    }

    public void addOrderItem(OrderItem orderItem){
        orderItem.setOrder(this);
        this.items.add(orderItem);
    }
}

Cascade 级联操作
CascadeType. PERSIST 级联持久化 ( 保存 ) 操作
CascadeType. MERGE 级联更新 ( 合并 ) 操作
CascadeType. REFRESH 级联刷新操作，只会查询获取操作
CascadeType. REMOVE 级联删除操作
CascadeType. ALL 级联以上全部操作
Fetch 抓取是否延迟加载，默认情况一的方为立即加载，多的一方为延迟加载
mappedBy 关系维护
mappedBy= "order" 表示在 OrderItem 类中的 order 属性来维护关系

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package com.hujuan.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 {

    private Integer id;
    private String productName;
    private Float sellPrice = 0f;
    private Order order;


    @Id @GeneratedValue
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    @Column(length=30,nullable=false)
    public String getProductName() {
        return productName;
    }
    public void setProductName(String productName) {
        this.productName = productName;
    }
    @Column(nullable=false)
    public Float getSellPrice() {
        return sellPrice;
    }
    public void setSellPrice(Float sellPrice) {
        this.sellPrice = sellPrice;
    }
    //optional=true表示该对象(Order)是可选的，对象(Order)可以不存在
    //值为false表示不可选即该对象(Order)必须存在，则在数据库中的外键就不能为null）
    @ManyToOne(cascade={CascadeType.MERGE,CascadeType.REFRESH},optional=false)
    //定义外键名称
    @JoinColumn(name="order_id")
    public Order getOrder() {
        return order;
    }
    public void setOrder(Order order) {
        this.order = order;
    }
}

本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/SuperBoo/archive/2009/12/30/5103913.aspx

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