Hibernate入门笔记
相关基础概念请从其它教材简单了解,这里仅记录下第一个Hibernate程序的实现步骤。
环境说明:
java开发工具:eclipse MARS.2 Release(4.5.2)
hibernate版本:hibernate-release-4.3.6.Final
Web 容器:Tomcat v8.0
数据库:MySQL 5.6.19-enterprise-commercial-advanced
jdbc驱动:mysql-connector-java-commercial-5.1.30-bin.jar
1.下载hibernate。
2.下载jdbc驱动文件。
3.在eclipse中新建web project,命名为firsthibernate。
4.拷贝hibernate/lib/required文件夹下的所有jar文件、以及jdbc驱动文件(此文件另外下载)到项目的WEB-INF/lib文件夹下,拷贝hibernate/project/etc下的hibernate.cfg.xml文件到项目的src目录下。
5.新建实体类Cat,Hibernate中配置实体类有两种方法:XML文件配置和@注解配置,本例采用@注解配置,相关注解代表的含义在代码中都有注明如下:
package com.levice.firsthibernate.bean; import java.util.Date; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.ManyToOne; import javax.persistence.Table; import javax.persistence.Temporal; import javax.persistence.TemporalType; @Entity //注解Entity表示该类能被Hibernate持久化 @Table(name = "tb_cat") //指定该Entity对应的数据表名 public class Cat { @Id //指定该列为主键。主键类型最好不要使用int等原始类型 @GeneratedValue(strategy = GenerationType.AUTO) //主键类型auto表示该主键为自增长型 private Integer id; @Column(name = "name") //指定该属性对应的数据库表的列为name,列名与属性名一样时这句注解可省略 private String name; @Column(name = "description") private String description; @ManyToOne //指定实体类之间的关系,本例表示多对一关系 @JoinColumn(name = "mother_id") private Cat mother; @Temporal(TemporalType.TIMESTAMP)//日期类型(DATE,TIME或TIMESTEMP) @Column(name = "birthday") private Date birthday; //getters and setters public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getDescription() { return description; } public void setDescription(String description) { this.description = description; } public Cat getMother() { return mother; } public void setMother(Cat mother) { this.mother = mother; } public Date getBirthday() { return birthday; } public void setBirthday(Date birthday) { this.birthday = birthday; } }
6.修改配置文件hibernate.cfg.xml,内容及注释如下:
<!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> <!-- 配置JDBC --> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.url">jdbc:mysql://localhost:3306/hibernate</property> <property name="connection.username">root</property> <property name="connection.password">123456</property> <!-- 指定使用MySQL数据库格式的SQL语句 --> <property name="dialect">org.hibernate.dialect.MySQLDialect</property> <!-- 指定在控制台打印生成的SQL语句 --> <property name="show_sql">true</property> <!-- 指定Hibernate启动时自动创建表结构 --> <property name="hbm2ddl.auto">create</property> <!-- 加上这一句以防止未知错误 --> <property name="current_session_context_class">thread</property> <!-- 指定Cat类为Hibernate实体类 --> <mapping class="com.levice.firsthibernate.bean.Cat"/> </session-factory> </hibernate-configuration>
7.初始化数据库,在MySQL中创建数据库hibernate,SQL代码如下:
create database hibernate;
8.配置HibernateUtil,就是修改HibernateUtil.java文件,这个文件在下载的hibernate文件中有,但我Copy过来的时候,一直没调试成功,于是采用了一个版本比较老的HibernateUtil。这个文件的作用是获取SessionFactory从而获取Session,不同版本的hiberate中获取SessionFactory的方法都不同,这里可以新建一个HibernateUtil.java文件,然后把下面的代码copy进去。
package com.levice.firsthibernate.util; import org.hibernate.SessionFactory; import org.hibernate.cfg.AnnotationConfiguration; @SuppressWarnings("deprecation") public class HibernateUtil { private static final SessionFactory sessionFactory; static{ try{ sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory(); }catch(Throwable ex){ System.err.println("Initial SessionFactory creation failed."); throw new ExceptionInInitializerError(ex); } } public static SessionFactory getSessionFactory(){ return sessionFactory; } }
9.执行Hibernate程序,创建一个包含主函数main的类CatTest,代码及注释如下:
package com.levice.firsthibernate.test; import java.awt.Font; import java.util.Date; import java.util.List; import javax.swing.JOptionPane; import org.hibernate.Session; import org.hibernate.Transaction; import com.levice.firsthibernate.bean.Cat; import com.levice.firsthibernate.util.HibernateUtil; public class CatTest { public static void main(String[] args) { // TODO Auto-generated method stub /*初始化几只Cat的信息*/ Cat mother = new Cat(); mother.setName("Mother White"); mother.setDescription("This is mother cat"); mother.setBirthday(new Date()); Cat kitty = new Cat(); kitty.setMother(mother); kitty.setName("Kitty"); kitty.setDescription("This is Kitty"); kitty.setBirthday(new Date()); Cat tom = new Cat(); tom.setMother(mother); tom.setName("Tom"); tom.setDescription("This is Tom"); tom.setBirthday(new Date()); @SuppressWarnings("static-access") Session session = new HibernateUtil().getSessionFactory().openSession(); //获取session并open,开启一个Hibernate会话 Transaction trans = session.beginTransaction(); //开启一个事务 session.persist(mother); //将mother保存到数据库 session.persist(kitty); session.persist(tom); @SuppressWarnings("all") List<Cat> catList = session.createQuery(" from Cat ").list(); //查询数据库中所有的猫 StringBuffer result = new StringBuffer(); result.append("all cats: \r\n\r\n"); for (Cat cc : catList) { result.append("name:" + cc.getName() + "\n"); result.append("mother:" + (cc.getMother() == null ? "null" : cc.getMother().getName()) + "\n"); result.append("description:" + cc.getDescription() + "\r\n\r\n"); } trans.commit(); //提交事务 session.close(); //关闭Hibernate会话 //用Swing显示查询结果 JOptionPane.getRootFrame().setFont(new Font("Arial", Font.BOLD, 14)); JOptionPane.showMessageDialog(null, result.toString()); } }
10.运行CatTest,可以看到如下输出:
控制台输出的SQL语句如下:
Hibernate: alter table tb_cat drop foreign key FK_dix3h50rxo8ahrcu5roir75n1 Hibernate: drop table if exists tb_cat Hibernate: create table tb_cat (id integer not null auto_increment, birthday datetime, description varchar(255), name varchar(255), mother_id integer, primary key (id)) Hibernate: alter table tb_cat add constraint FK_dix3h50rxo8ahrcu5roir75n1 foreign key (mother_id) references tb_cat (id) Hibernate: insert into tb_cat (birthday, description, mother_id, name) values (?, ?, ?, ?) Hibernate: insert into tb_cat (birthday, description, mother_id, name) values (?, ?, ?, ?) Hibernate: insert into tb_cat (birthday, description, mother_id, name) values (?, ?, ?, ?) Hibernate: select cat0_.id as id1_0_, cat0_.birthday as birthday2_0_, cat0_.description as descript3_0_, cat0_.mother_id as mother_i5_0_, cat0_.name as name4_0_ from tb_cat cat0_