Hibernate 一對多關系操作

這里使用類別Category和產品Product舉例。

Category與Product屬于1:m 的關系，數據庫如下：

那么，實體設計如下：

package com.sasa.domain;

import java.util.Date;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class Category {

    public Category() {}
    
    private Integer id;
    private String c_name;
    private String descr;
    private Date create_tm;
    
    private Set<Product> Products = new HashSet<Product>();
    
    
    public Set<Product> getProducts() {
        return Products;
    }
    public void setProducts(Set<Product> products) {
        Products = products;
    }
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getC_name() {
        return c_name;
    }
    public void setC_name(String c_name) {
        this.c_name = c_name;
    }
    public String getDescr() {
        return descr;
    }
    public void setDescr(String descr) {
        this.descr = descr;
    }
    public Date getCreate_tm() {
        return create_tm;
    }
    public void setCreate_tm(Date create_tm) {
        this.create_tm = create_tm;
    }
    @Override
    public String toString() {
        return "Category [id=" + id + ", c_name=" + c_name + ", descr=" + descr + ", create_tm=" + create_tm
                + ", Products=" + Products + "]";
    }
    
}

package com.sasa.domain;

import java.time.LocalDateTime;

public class Product {
    
    public Product() {}
    
    private Integer pid;
    private String pname;
    private Double price;
    private LocalDateTime create_tm;
    private Category category;
    
    public Category getCategory() {
        return category;
    }
    public void setCategory(Category category) {
        this.category = category;
    }
    public Integer getPid() {
        return pid;
    }
    public void setPid(Integer pid) {
        this.pid = pid;
    }
    public String getPname() {
        return pname;
    }
    public void setPname(String pname) {
        this.pname = pname;
    }
    public Double getPrice() {
        return price;
    }
    public void setPrice(Double price) {
        this.price = price;
    }
    
    public LocalDateTime getCreate_tm() {
        return create_tm;
    }
    public void setCreate_tm(LocalDateTime create_tm) {
        this.create_tm = create_tm;
    }
    @Override
    public String toString() {
        return "Product [pid=" + pid + ", pname=" + pname + ", price=" + price + ", create_tm=" + create_tm
                + ", category=" + category + "]";
    }
    
    
    
}

配置文件：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
    <hibernate-mapping package="com.sasa.domain">
        <class name="Category" table="category">
            <id name="id" column="id">
                <generator class="native"></generator>
            </id>
            <property name="c_name"></property>
            <property name="descr"></property>
            <property name="create_tm"></property>
            <set name="products">
                <key column="category_id"></key>
                <one-to-many class="Product"/>
            </set>
        </class>
    </hibernate-mapping>

name：引用屬性名

column：外鍵名稱

class：與此類相關的類的完整類名

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
    <hibernate-mapping package="com.sasa.domain">
        <class name="Product" table="product">
            <id name="pid" column="pid">
                <generator class="native"></generator>
            </id>
            <property name="pname"></property>
            <property name="price"></property>
            <property name="create_tm"></property>
            <many-to-one name="category" column="category_id" class="Category"></many-to-one>
        </class>
    </hibernate-mapping>

當設計好之后，就可以書寫代碼測試了：

package com.sasa.service;

import java.time.LocalDateTime;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.junit.Test;

import com.sasa.domain.Category;
import com.sasa.domain.Product;
import com.sasa.utils.HibernateUtils;

public class CategoryService {
    @Test
    //新增類別和產品
    public void addCategorys(){
        Session session = HibernateUtils.getCurrentSession();
        Transaction tran = session.beginTransaction();
    //========================================
        Category category = new Category();
        category.setC_name("運動器材");
        category.setDescr("sport");
        
        Product p1 = new Product();
        p1.setPname("足球");
        p1.setPrice(100.00);
        
        Product p2 = new Product();
        p2.setPname("籃球");
        p2.setPrice(90.00);
        
        //一對多
        category.getProducts().add(p1);
        category.getProducts().add(p2);
        
        //多對一
        p1.setCategory(category);
        p2.setCategory(category);
        
        session.save(category);
        session.save(p1);
        session.save(p2);
    //==========================================    
        tran.commit();
        session.close();
        
    }
    
    
    //為類別增加產品
    public void addProductByCategory() {
        Session session = HibernateUtils.getCurrentSession();
        Transaction tran = session.beginTransaction();
        
        //====================================
        
        //1、獲得要操作的類別  2、創(chuàng)建產品  3、將產品添加到類別，將類別設置到產品  4、執(zhí)行保存
        Category category = session.get(Category.class, 9);
        
        Product product = new Product();
        product.setPname("羽毛球");
        product.setCreate_tm(LocalDateTime.now());
        product.setPrice(40.50);
        
        category.getProducts().add(product);
        product.setCategory(category);
        
        session.save(product);
        
        //====================================
        
        tran.commit();
        session.close();
    }
    
    
    //刪除產品
    public void delProductByCategory() {
        Session session = HibernateUtils.getCurrentSession();
        Transaction tran = session.beginTransaction();
        
        //====================================
        
        //1、獲得要操作的類別  2、獲得要移除的產品  3、將產品從類別集合中移除 
        Category category = session.get(Category.class, 9);
        
        Product product = session.get(Product.class, 35);
        
        category.getProducts().remove(product);
        product.setCategory(null);//注意：數據庫外鍵需設計為可空 這里的刪除是將外鍵設置為null， 執(zhí)行的是update，不執(zhí)行delete
        
        //====================================
        //
        tran.commit();
        session.close();
    }

}

HibernateUtils.java:

package com.sasa.utils;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtils {

    private static SessionFactory sessionFac;
    
    static {
        // Configuration 配置加載類，加載主配置，orm元數據加載
                Configuration conf = new Configuration().configure();
                // SessionFactory 創(chuàng)建用于操作數據庫的Session工廠
                // SessionFactory 負責保存和使用所有配置，消耗內存資源非常大
                // 線程安全
                // 保證在web項目中，只創(chuàng)建一個SessionFactory
             sessionFac = conf.buildSessionFactory();
    }
    
    //獲得Session
    //打開一個全新的Session
    public static Session openSession() {
        Session session = sessionFac.openSession();
        return session;
    }

    //獲得線程上綁定的Session
    public static Session getCurrentSession() {
        Session session = sessionFac.getCurrentSession();
        return session;
    }

}

posted @ 2019-10-12 15:55 SasaL Views(177) Comments(0) 收藏舉報

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Hibernate 一對多關系操作

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