Hibernate实战——组件作为复合主键

爱被打了一巴掌 2021-07-24 16:12 363阅读 0赞

**一 配置文件**

<?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="hbm2ddl.auto">update</property>
               
               <property name="show_sql">true</property>
               
               <property name="hibernate.format_sql">true</property>
               
               <mapping class="org.crazyit.app.domain.Person"/>
         </session-factory>
    </hibernate-configuration>

**二 PO**

1 Person

package org.crazyit.app.domain;
    
    import java.util.*;
    import javax.persistence.*;
    
    @Entity
    @Table(name="person_inf")
    public class Person
    {
        // 以Name组件作为标识属性
        @EmbeddedId
        @AttributeOverrides({
            // 指定
            @AttributeOverride(name="first",
                column = @Column(name="person_firstname")),
            @AttributeOverride(name="last",
                column = @Column(name="person_lastname"))
        })
        private Name name;
        private int age;
    
        // name的setter和getter方法
        public void setName(Name name)
        {
            this.name = name;
        }
        public Name getName()
        {
            return this.name;
        }
    
        // age的setter和getter方法
        public void setAge(int age)
        {
            this.age = age;
        }
        public int getAge()
        {
            return this.age;
        }
    }

2 Name

package org.crazyit.app.domain;
    import java.util.*;
    
    public class Name
         implements java.io.Serializable
    {
         // 定义first成员变量
         private String first;
         // 定义last成员变量
         private String last;
         // 无参数的构造器
         public Name()
         {
         }
         // 初始化全部成员变量的构造器
         public Name(String first , String last)
         {
               this.first = first;
               this.last = last;
         }
         // first的setter和getter方法
         public void setFirst(String first)
         {
               this.first = first;
         }
         public String getFirst()
         {
               return this.first;
         }
         // last的setter和getter方法
         public void setLast(String last)
         {
               this.last = last;
         }
         public String getLast()
         {
               return this.last;
         }
         // 重写equals()方法，根据first、last进行判断
         public boolean equals(Object obj)
         {
               if (this == obj)
               {
                    return true;
               }
               if (obj != null && obj.getClass() == Name.class)
               {
                    Name target = (Name)obj;
                    return target.getFirst().equals(getFirst())
                         && target.getLast().equals(getLast());
               }
               return false;
         }
         // 重写hashCode()方法，根据first、last计算hashCode值
         public int hashCode()
         {
               return getFirst().hashCode() * 31
                    + getLast().hashCode();
         }
    }

**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 PersonManager
    {
        public static void main(String[] args)
        {
            PersonManager mgr = new PersonManager();
            mgr.createAndStorePerson();
            HibernateUtil.sessionFactory.close();
        }
    private void createAndStorePerson()
    {
        Session session = HibernateUtil.currentSession();
        Transaction tx = session.beginTransaction();
        // 创建Person对象
        Person person = new Person();
        // 为Person对象设置属性
        person.setAge(21);
        // 创建一个Name对象作为Person对象的标识属性值
        person.setName(new Name("crazyit.org" , "疯狂Java联盟"));
        session.save(person);
        tx.commit();
        HibernateUtil.closeSession();
    }
    }

**四 测试**

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