Hibernate实战——复合主键的成员属性为关联实体

悠悠 2021-07-24 20:29 357阅读 0赞

**一 配置**

<?xml version="1.0" encoding="GBK"?>
    
    <!DOCTYPE hibernate-configuration PUBLIC
         "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
         "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
    
    <hibernate-configuration>
         <session-factory>
               
               <property  name="connection.driver_class">com.mysql.jdbc.Driver</property>
               
               <property  name="connection.url">jdbc:mysql://localhost/hibernate</property>
               
               <property name="connection.username">root</property>
               
               <property name="connection.password">32147</property>
               
               <property  name="hibernate.c3p0.max_size">20</property>
               
               <property name="hibernate.c3p0.min_size">1</property>
               
               <property  name="hibernate.c3p0.timeout">5000</property>
               
               <property  name="hibernate.c3p0.max_statements">100</property>
               <property  name="hibernate.c3p0.idle_test_period">3000</property>
               <property  name="hibernate.c3p0.acquire_increment">2</property>
               <property  name="hibernate.c3p0.validate">true</property>
               
               <property  name="dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>
               <property name="hibernate.format_sql">true</property>
               <property name="hibernate.show_sql">true</property>
               
               <property name="hbm2ddl.auto">update</property>
               
               <mapping class="org.crazyit.app.domain.Order"/>
               <mapping class="org.crazyit.app.domain.OrderItem"/>
               <mapping class="org.crazyit.app.domain.Product"/>
         </session-factory>
    </hibernate-configuration>

**二 PO**

1 Product

package org.crazyit.app.domain;
    import javax.persistence.*;
    
    @Entity
    @Table(name="product_inf")
    public class Product
    {
         // 定义标识属性
         @Id @Column(name="product_id")
         @GeneratedValue(strategy=GenerationType.IDENTITY)
         private Integer productId;
         private String name;
         // 无参数的构造器
         public Product(){}
         // 初始化全部属性的构造器
         public Product(String name)
         {
               this.name = name;
         }
         // productId的setter和getter方法
         public void setProductId(Integer productId)
         {
               this.productId = productId;
         }
         public Integer getProductId()
         {
               return this.productId;
         }
         // name的setter和getter方法
         public void setName(String name)
         {
               this.name = name;
         }
         public String getName()
         {
               return this.name;
         }
    }

2 OrderItem

package org.crazyit.app.domain;
    
    import java.util.Date;
    import java.util.HashSet;
    import java.util.Set;
    
    import javax.persistence.*;
    
    @Entity
    @Table(name="order_inf")
    public class Order
    {
        // 定义标识属性
        @Id @Column(name="order_id")
        @GeneratedValue(strategy=GenerationType.IDENTITY)
        private Integer orderId;
        private Date orderDate;
        // 关联的的订单项
        @OneToMany(targetEntity=OrderItem.class, mappedBy="order")
        private Set<OrderItem> items
            = new HashSet<>();
    
        // 无参数的构造器
        public Order(){}
    
        // 初始化全部成员变量的构造器
        public Order(Date orderDate)
        {
            this.orderDate = orderDate;
        }
    
        // orderId的setter和getter方法
        public void setOrderId(Integer orderId)
        {
            this.orderId = orderId;
        }
        public Integer getOrderId()
        {
            return this.orderId;
        }
    
        // orderDate的setter和getter方法
        public void setOrderDate(Date orderDate)
        {
            this.orderDate = orderDate;
        }
        public Date getOrderDate()
        {
            return this.orderDate;
        }
    
        // items的setter和getter方法
        public void setItems(Set<OrderItem> items)
        {
            this.items = items;
        }
        public Set<OrderItem> getItems()
        {
            return this.items;
        }
    }

3 Order

package org.crazyit.app.domain;
    import javax.persistence.*;
    
    @Entity
    @Table(name="order_item_inf")
    public class OrderItem
         implements java.io.Serializable
    {
         // 下面3个属性将作为联合主键
         // 定义关联的Order实体
         @ManyToOne(targetEntity=Order.class)
         // 映射名为order_id的外键列，参照order_inf的order_id主键列
         @JoinColumn(name="order_id" ,  referencedColumnName="order_id")
         @Id
         private Order order;
         // 定义关联的Product实体
         @ManyToOne(targetEntity=Product.class)
         // 映射名为product_id的外键列，参照product_inf的product_id主键列
         @JoinColumn(name="product_id" ,  referencedColumnName="product_id")
         @Id
         private Product product;
         // 该订单项订购的产品数量
         @Id
         private int count;
         // 无参数的构造器
         public OrderItem(){ }
         // 初始化全部成员变量的构造器
         public OrderItem(Order order , Product product , int  count)
         {
               this.order = order;
               this.product = product;
               this.count = count;
         }
         // order的setter和getter方法
         public void setOrder(Order order)
         {
               this.order = order;
         }
         public Order getOrder()
         {
               return this.order;
         }
         // product的setter和getter方法
         public void setProduct(Product product)
         {
               this.product = product;
         }
         public Product getProduct()
         {
               return this.product;
         }
         // count的setter和getter方法
         public void setCount(int count)
         {
               this.count = count;
         }
         public int getCount()
         {
               return this.count;
         }
         // 重写equals()方法，根据product、order、count判断是否相等
         public boolean equals(Object obj)
         {
               if(this == obj)
               {
                    return true;
               }
               if(obj != null && obj.getClass() == OrderItem.class)
               {
                    OrderItem target = (OrderItem)obj;
                    return this.order.equals(target.getOrder())
                         &&  this.product.equals(target.getProduct())
                         && this.count == target.getCount();
               }
               return false;
         }
         // 重写hashCode()方法，根据product、order、count计算hashCode值
         public int hashCode()
         {
               return (this.product == null ? 0 :  this.product.hashCode()) * 31 * 31
                    + (this.order == null ? 0 : this.order.hashCode()) * 31
                    + this.count;
         }
    }

**三 测试**

1 工具类

package lee;
    
    import org.hibernate.*;
    import org.hibernate.cfg.*;
    import org.hibernate.service.*;
    import org.hibernate.boot.registry.*;
    
    public class HibernateUtil
    {
        public static final SessionFactory sessionFactory;
    
        static
        {
            try
            {
                // 使用默认的hibernate.cfg.xml配置文件创建Configuration实例
                Configuration cfg = new Configuration()
                    .configure();
                // 以Configuration实例来创建SessionFactory实例
                ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder()
                    .applySettings(cfg.getProperties()).build();
                sessionFactory = cfg.buildSessionFactory(serviceRegistry);
            }
            catch (Throwable ex)
            {
                System.err.println("Initial SessionFactory creation failed." + ex);
                throw new ExceptionInInitializerError(ex);
            }
        }
    
        // ThreadLocal可以隔离多个线程的数据共享，因此不再需要对线程同步
        public static final ThreadLocal<Session> session
            = new ThreadLocal<Session>();
    
        public static Session currentSession()
            throws HibernateException
        {
            Session s = session.get();
            // 如果该线程还没有Session,则创建一个新的Session
            if (s == null)
            {
                s = sessionFactory.openSession();
                // 将获得的Session变量存储在ThreadLocal变量session里
                session.set(s);
            }
            return s;
        }
    
        public static void closeSession()
            throws HibernateException
        {
            Session s = session.get();
            if (s != null)
                s.close();
            session.set(null);
        }
    }

2 测试类

package lee;
    
    import org.hibernate.Transaction;
    import org.hibernate.Session;
    
    import java.util.*;
    import org.crazyit.app.domain.*;
    
    public class OrderManager
    {
        public static void main(String[] args)
        {
            OrderManager mgr = new OrderManager();
            mgr.createAndStoreOrder();
            HibernateUtil.sessionFactory.close();
        }
        private void createAndStoreOrder()
        {
            Session sess = HibernateUtil.currentSession();
            Transaction tx = sess.beginTransaction();
    
            Order order = new Order(new Date());
            Product p1 = new Product("键盘");
            Product p2 = new Product("显示器");
            OrderItem item1 = new OrderItem(order , p1 , 50);
            OrderItem item2 = new OrderItem(order , p2 , 18);
    
            sess.save(order);
            sess.save(p1);
            sess.save(p2);
            sess.save(item1);
            sess.save(item2);
    
            tx.commit();
            HibernateUtil.closeSession();
        }
    }

**四 测试**

Hibernate:
        insert
        into
            order_inf
            (orderDate)
        values
            (?)
    Hibernate:
        insert
        into
            product_inf
            (name)
        values
            (?)
    Hibernate:
        insert
        into
            product_inf
            (name)
        values
            (?)
    Hibernate:
        insert
        into
            order_item_inf
            (product_id, order_id, count)
        values
            (?, ?, ?)
    Hibernate:
        insert
        into
            order_item_inf
            (product_id, order_id, count)
        values
            (?, ?, ?)

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