Hibernate: 三种状态和CRUD四种操作

本篇博客是初学hibernate时笔记总结，主要总结hibernate的三种状态和hibernate的CRUD操作。

1. hibernate的三种状态：

• Transient State : 瞬时状态；
• Persistent State : 持久状态；
• Detached State : 离线状态或托管状态；

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• Transient State : 瞬时状态：
  当我们new操作符初始化一个对象时，它处于瞬时态，也就是他没有任何和数据库表相关的行为，只要应用程序不再引用这些对象，它们状态将会丢失，被jvm垃圾回收了。总结，这个对象，Session没管理，数据库中没存。
• Persistent State : 持久状态 :
  持久化实例则是具有数据库标识的实例，它由持久化管理器Session统一管理的，只要它的状态发生改变，在事务提交时，会同步到数据库中。
• Detached State : 离线状态或托管状态 ： 数据库中有，但是session不管理了，

具体的分析推荐一篇博客写的很详细，也很容易理解，

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Hibernate三种状态的详解，

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2.CRUD操作；

2.1 Bean对象

package com.qian.domain;import java.util.Date;public class User2 {    private String user2Id;    private String user2Name;    private Date user2CreateDate;    public String getUser2Id() {        return user2Id;    }    public void setUser2Id(String user2Id) {        this.user2Id = user2Id;    }    public String getUser2Name() {        return user2Name;    }    public void setUser2Name(String user2Name) {        this.user2Name = user2Name;    }    public Date getUser2CreateDate() {        return user2CreateDate;    }    public void setUser2CreateDate(Date user2CreateDate) {        this.user2CreateDate = user2CreateDate;    }}

User2.hbm.xml文件

<?xml version="1.0" encoding="UTF-8"?><!--  ~ Hibernate, Relational Persistence for Idiomatic Java  ~  ~ License: GNU Lesser General Public License (LGPL), version 2.1 or later.  ~ See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.  --><!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.qian.domain">    <class name="User2" table="t_User2">        <id name="user2Id" column="User2_ID">            <generator class="uuid"/>        </id>        <property name="user2Name"/>        <property name="user2CreateDate"/>    </class></hibernate-mapping>

hibernate.cfg.xml文件

<?xml version="1.0" encoding="UTF-8"?><!--  ~ Hibernate, Relational Persistence for Idiomatic Java  ~  ~ License: GNU Lesser General Public License (LGPL), version 2.1 or later.  ~ See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.  --><!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>        <!-- Database connection settings -->        <property name="connection.driver_class">oracle.jdbc.OracleDriver</property>        <property name="connection.url">jdbc:oracle:thin:@localhost:1521:ORCL</property>        <property name="connection.username">scott</property>        <property name="connection.password">qian</property>        <!-- JDBC connection pool (use the built-in) -->        <property name="connection.pool_size">1</property>        <!-- SQL dialect -->        <property name="dialect">org.hibernate.dialect.OracleDialect</property>        <!-- Disable the second-level cache  -->        <property name="cache.provider_class">org.hibernate.cache.internal.NoCacheProvider</property>        <!-- Echo all executed SQL to stdout -->        <property name="show_sql">true</property>        <!-- Drop and re-create the database schema on startup         <property name="hbm2ddl.auto">create</property>        -->        <mapping resource="com/qian/domain/User.hbm.xml"/>        <mapping resource="com/qian/domain/User2.hbm.xml"/>    </session-factory></hibernate-configuration>

hbm2ddl类

package com.qian.envir;import java.util.EnumSet;import org.hibernate.boot.MetadataSources;import org.hibernate.boot.registry.StandardServiceRegistry;import org.hibernate.boot.registry.StandardServiceRegistryBuilder;import org.hibernate.boot.spi.MetadataImplementor;import org.hibernate.cfg.Configuration;import org.hibernate.tool.hbm2ddl.SchemaExport;import org.hibernate.tool.schema.TargetType;/** * http://blog.csdn.net/qinshijangshan/article/details/53314230 * http://bbs.csdn.net/topics/391942178?page=1 * 参考网页来分析所在版本的不同SchemaExport变化的集中方式， * <property name="hbm2ddl.auto">create</property> * @author Administrator * */public class ExoprotDB {    public static void main(String[] args) {        StandardServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().configure().build();        MetadataImplementor metadataImplementor = (MetadataImplementor) new MetadataSources(serviceRegistry)                .buildMetadata();        SchemaExport export = new SchemaExport();        export.create(EnumSet.of(TargetType.DATABASE), metadataImplementor);    }}

HibernateUtil类

package com.qian.envir;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.boot.MetadataSources;import org.hibernate.boot.registry.StandardServiceRegistry;import org.hibernate.boot.registry.StandardServiceRegistryBuilder;public class HibernateUtil {    private static SessionFactory sessionFactory;    //生成sessionFactory;    static{        final StandardServiceRegistry standardServiceRegistry = new                StandardServiceRegistryBuilder().configure().build();        try{            sessionFactory = new MetadataSources(standardServiceRegistry)                    .buildMetadata().buildSessionFactory();                 }catch(Exception e){            StandardServiceRegistryBuilder.destroy(standardServiceRegistry);        }    }    public static SessionFactory getSessionFactory(){        return sessionFactory;    }    public static Session getSession(){        return sessionFactory.openSession();    }    public static void freeSession(Session session){        if(session!=null){            if(session.isOpen()){                session.close();            }        }    }}

CRUD测试类代码

package test.qian;import java.util.Date;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction;import com.qian.domain.User2;import com.qian.envir.HibernateUtil;import junit.framework.TestCase;public class CRUDTest extends TestCase {    public void testCreate(){        //step one：读取hibernate.cfg.xml文件拿到sessionFactory        //由于sessionFactory相当于DB的镜像，并且创建很花时间，我们可以写一个工具类只创建一次；        SessionFactory sessionFactory = HibernateUtil.getSessionFactory();        Session session = null;        Transaction transaction = null;        try{        //stpe two: 通过sessionFactroy拿到session            session = sessionFactory.openSession();        //step three: 开启事务-->提交是否-->捕获异常事务回滚            transaction = session.getTransaction();            transaction.begin();        //step four: 写添加用户的测试代码            User2 user2 = new User2();            user2.setUser2Id("u2id");            user2.setUser2Name("userName");            user2.setUser2CreateDate(new Date());        //step five: 保存到数据库中            session.save(user2);            transaction.commit();        }catch(Exception e){            transaction.rollback();            e.printStackTrace();        }finally{        //step six: 无论成功与否释放session            HibernateUtil.freeSession(session);        }    }    public void testReadByGet(){        //step one:        SessionFactory sessionFactory = HibernateUtil.getSessionFactory();        Session session =null;        Transaction transaction = null;        try{            //step two:            session = sessionFactory.openSession();            //step three:            transaction = session.getTransaction();            transaction.begin();            //step four:            //get方法的第一个参数为 Class对象, 第二个参数为Serializable类型(key)，也就是根据id查值            //get方法获取的对象是持久化对象,如果没有找到则返回null,不会报错。            //发出get查询,它就会马上去数据库中查找,因为是持久化对象,如果我们改变了对象的属性,在最后            //的commit是,及时没有update,Hibernate也会对照数据库中的对象和内存中的对象，对数据进行更改;            User2 user2 = session.get(User2.class, "402880da5e50fc2d015e50fc30b10000");            if(user2!=null)                System.out.println(user2.getUser2Name()+" : "+user2.getUser2CreateDate());            //user2.setUser2Name("如果这里对属性操作，会同步到数据库");            transaction.commit();        }catch(Exception e){            transaction.rollback();            e.printStackTrace();        }finally{            HibernateUtil.freeSession(session);        }    }    public void testReadByLoad(){        //step one:        SessionFactory sessionFactory = HibernateUtil.getSessionFactory();        Session session =null;        Transaction transaction = null;        try{            //step two:            session = sessionFactory.openSession();            //step three:            transaction = session.getTransaction();            transaction.begin();            //step four:            //load方法的第一个参数为 Class对象, 第二个参数为Serializable类型(key)，也就是根据id查值            //load方法获取的对象是持久化对象,如果没有找到则抛出对象没找到异常。            //发出load查询,它不会马上去数据库中查找,而是创建一个User2的代理对象，当真正用的时候才会            //向数据库发出查询语句。也就是load使用CGLIB的动态代理来实现懒加载的。            //的commit是,及时没有update,Hibernate也会对照数据库中的对象和内存中的对象，对数据进行更改;            User2 user2 = session.load(User2.class, "402880da5e50fc2d015e50fc30b10000");            System.out.println(user2.getUser2Name()+" : "+user2.getUser2CreateDate());            user2.setUser2Name("如果持久化对象 对属性操作，会同步到数据库");            transaction.commit();        }catch(Exception e){            transaction.rollback();            e.printStackTrace();        }finally{            HibernateUtil.freeSession(session);        }    }    public void testUpdate(){        //step one:        SessionFactory sessionFactory = HibernateUtil.getSessionFactory();        Session session =null;        Transaction transaction = null;        try{        //step two:            session = sessionFactory.openSession();        //step three:            transaction = session.getTransaction();            transaction.begin();        //step four:            User2 user2 = session.load(User2.class, "402880da5e50fc2d015e50fc30b10000");            user2.setUser2Name("zhangSan");        //step five:            session.update(user2);            transaction.commit();        }catch(Exception e){            transaction.rollback();            e.printStackTrace();        }finally{            HibernateUtil.freeSession(session);        }    }    public void testDelete(){        //step one:        SessionFactory sessionFactory = HibernateUtil.getSessionFactory();        Session session =null;        Transaction transaction = null;        try{            //step two:            session = sessionFactory.openSession();            //step three:            transaction = session.getTransaction();            transaction.begin();            //step four:            User2 user2 = session.load(User2.class, "402880da5e50fc2d015e50fc30b10000");            session.delete(user2);            System.out.println("delete successfully");            transaction.commit();        }catch(Exception e){            transaction.rollback();            e.printStackTrace();        }finally{            HibernateUtil.freeSession(session);        }    }}