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;
    }
    //級聯操作
    @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;
    }
    //級聯操作
    @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 級聯操作
CascadeType. PERSIST 級聯持久化 ( 保存 ) 操作
CascadeType. MERGE 級聯更新 ( 合并 ) 操作
CascadeType. REFRESH 級聯刷新操作，只會查詢獲取操作
CascadeType. REMOVE 級聯刪除操作
CascadeType. ALL 級聯以上全部操作
Fetch 抓取是否延遲加載，默認情況一的方為立即加載，多的一方為延遲加載
mappedBy 關系維護
mappedBy= "order" 表示在 OrderItem 類中的 order 屬性來維護關系

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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表示該對象(Order)是可選的，對象(Order)可以不存在
    //值為false表示不可選即該對象(Order)必須存在，則在數據庫中的外鍵就不能為null）
    @ManyToOne(cascade={CascadeType.MERGE,CascadeType.REFRESH},optional=false)
    //定義外鍵名稱
    @JoinColumn(name="order_id")
    public Order getOrder() {
        return order;
    }
    public void setOrder(Order order) {
        this.order = order;
    }
}

本文來自CSDN博客，轉載請標明出處：http://blog.csdn.net/SuperBoo/archive/2009/12/30/5103913.aspx

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