Hibernate批量更新实战

た入场券 2021-07-24 22:09 486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="hbm2ddl.auto">update</property>
               
               <property name="show_sql">false</property>
               
               <property name="hibernate.format_sql">false</property>
               
               <mapping class="org.crazyit.app.domain.User"/>
         </session-factory>
    </hibernate-configuration>

**二 PO**

package org.crazyit.app.domain;
    import javax.persistence.*;
    
    @Entity
    @Table(name="user_inf")
    public class User
    {
         // 定义标识属性
         @Id @Column(name="user_id")
         @GeneratedValue(strategy=GenerationType.IDENTITY)
         private Integer id;
         private String name;
         private int age;
         private String nationality;
         // 无参数的构造器
         public User()
         {
         }
         // 初始化全部成员变量的构造器
         public User(String name , int age , String nationality)
         {
               this.name = name;
               this.age = age;
               this.nationality = nationality;
         }
         // id的setter和getter方法
         public void setId(Integer id)
         {
               this.id = id;
         }
         public Integer getId()
         {
               return this.id;
         }
         // name的setter和getter方法
         public void setName(String name)
         {
               this.name = name;
         }
         public String 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;
         }
         // nationality的setter和getter方法
         public void setNationality(String nationality)
         {
               this.nationality = nationality;
         }
         public String getNationality()
         {
               return this.nationality;
         }
    }

**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.*;
    
    import org.crazyit.app.domain.*;
    
    public class UserManager
    {
        public static void main(String[] args)throws Exception
        {
            UserManager mgr = new UserManager();
            mgr.updateUsers();
            HibernateUtil.sessionFactory.close();
        }
        private void updateUsers()throws Exception
        {
            // 打开Session
            Session session = HibernateUtil.currentSession();
            // 开始事务
            Transaction tx = session.beginTransaction();
            // 查询出User表中的所有记录
            ScrollableResults users = session.createQuery("from User")
                .setCacheMode(CacheMode.IGNORE)
                .scroll(ScrollMode.FORWARD_ONLY);
            int count=0;
            // 遍历User表中的全部记录
            while ( users.next() )
            {
                User u = (User) users.get(0);
                u.setName("新用户名" + count);
                // 当count为20的倍数时，
                // 将更新的结果从Session中flush到数据库。
                if ( ++count % 20 == 0 )
                {
                    session.flush();
                    session.clear();
                }
            }
            tx.commit();
            HibernateUtil.closeSession();
        }
    }

**四 测试**

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