首先要导入包,将下载的hibernate所有required包导入,将下载的hibernate用来写log的slf4j的api和nopjar包导入,将下载的mysql链接引擎jar包导入。
然后新建java工程。
先告诉hiernate怎么连数据库:在hibernate默认识别目录src根目录下以默认hibernate配置文件名hibernate.cfg.xml建立xml(都采用默认可以省去在代码中书写路径和名字的麻烦):
<?xml version='1.0' encoding='utf-8'?>
<!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">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">mysql</property>
<!--
<property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
<property name="connection.url">jdbc:oracle:thin:@localhost:1521:SXT</property>
<property name="connection.username">scott</property>
<property name="connection.password">tiger</property>
<property name="dialect">org.hibernate.dialect.OracleDialect</property>
-->
<!-- JDBC connection pool (use the built-in) -->
<!-- <property name="connection.pool_size">1</property> 数据库连接池大小 -->
<!-- SQL dialect sql语句方言-->
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<!-- Enable Hibernate's automatic session context management -->
<!-- <property name="current_session_context_class">thread</property>
指定getCurrentSession的上下文,如果不指定只能用openSession。有thread(当前线程),jta,managed(jee、EJB中使用applicationserver,且要手工管理currentSession手工管理事务的时候要用该值),custom.class(自定义class管理currentSession)
jta:java transaction api,java中一种用于管理事务的api,和实现了该api的应用服务器的JTATransactionManager结合使用可以处理分布存储。
-->
<!-- 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>
<property name="format _sql">true</property>
<!-- Drop and re-create the database schema on startup -->
<!-- <property name="hbm2ddl.auto">update</property>
-->
<mapping resource="com/test/hibernate/model/Student.hbm.xml"/>
<mapping class="com.test.hibernate.model.Teacher"/>
</session-factory>
</hibernate-configuration>
然后告诉hibernate数据库和model的映射关系,也采用默认目录和命名方式:
在model(这里是Student类)所在目录下新建Student.hbm.xml,名字要和类名一致,对于Teacher类,因为使用了注解所以不需要,也可以看出来使用注解相对来说比较方便。
配置文件中如果表名和类名不一致也可以指定表名,参见本文末尾处的一段配置
<?xml version="1.0"?>
<!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.test.hibernate.model">
<class name="Student">
<id name="id"></id>
<property name="name"></property>
<property name="age"></property>
</class>
</hibernate-mapping>
数据库也一致,只有三列,其中id是主键。
指定id生成策略示例代码:
<id name="id">
<generator class="uuid"></generator>
<!-- 指定数据库该主键生成策略为uuid,uuid要求主键必须是个字符串才能采用,uuid全局唯一id。指定生成策略后就不需要手动设置主键了。
还可以设成:native,int型,会根据数据库本地自动生成。
关于生成策略更多内容参见hibernate API "5.1.2.2.1. Various additional generators" -->
</id>
Student类:
package com.test.hibernate.model;
public class Student {
private int id;
private String name;
private int age;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
Teacher类:
package com.test.hibernate.model;
import javax.persistence.*;
import java.util.Date;
@Entity //实体类 表示和数据库内容一一对应,无需额外书写映射关系xml
//@Table(name = “_Teacher”) 如果表名和类名不一致(不区分大小写),可以用这个注解来标明表名
public class Teacher {
private int id;
private String name;
private String title;
private Date birthDate;
@Id //主键
//@Basic //对于和数据对应的字段可以写,相当于加了
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
@Column(name=”_name”)//字段名和属性名不对应时可以这样指定对应的属性名
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
//如果不想往数据库中存放,可以加个注解,透明的—@Transient
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
//可以只保存录入时间的日期部分或者时间部分@Temporal(TemporalType.DATE),这样数据库中就会用DATE类型来保存数据,默认是DATETIME,日期时间一起保存
public Date getBirthDate(){
return birthDate;
}
public void setBirthDate(Date birthDate){
this.birthDate=birthDate;
}
}
关于用注解的方式指定主键生成策略:
@GeneratedValue 默认策略AUTO,相当于xml中的native,会使数据库根据本地策略自动生成,如果是mysql会auto increament,如果是oracle则sequence。
@GeneratedValue(strategy = GenerationType.IDENTITY)
@GeneratedValue(strategy = GenerationType.SEQUENCE)
@SequenceGenerator(name="thissequencegeneratorname",sequenceName="aa")定义一个generator前者是它自己的名字,后者是它采用的数据库中的生成器的名字,定义要写在@Entity下面,类上面。下面这一行是采用该generator
@GeneratedValue(strategy = GenerationType.SEQUENCE,generator="thissequencegeneratorname")
@Entity
@javax.persistence.TableGenerator(
name="Teacher_GEN",
table="GENERATOR_TABLE",
pkColumnName = "pk_key",
valueColumnName = "pk_value",
pkColumnValue="Teacher",
allocationSize=1
)//表生成器,可以跨数据库平台
@Id
@GeneratedValue(strategy=GenerationType.TABLE, generator="Teacher_GEN")
public int getId() {
return id;
}
然后就可以写测试类了:
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
import com.test.hibernate.model.Student;
public class StudentTest {
public static void main(String args[]){
Student s = new Student();
s.setId(1);
s.setName("s2");
s.setAge(1);
Configuration cfg = new Configuration();
//SessionFactory sf = cfg.configure().buildSessionFactory();
cfg.configure();//解析所有hibernate的配置xml,不指定参数就会去找默认目录下的xml
ServiceRegistry sr = new ServiceRegistryBuilder().applySettings(cfg.getProperties()).buildServiceRegistry();
SessionFactory sf = cfg.buildSessionFactory(sr);//生成session工厂,相当于产生数据库连connection的工厂
Session session = sf.openSession();//相当于数据库的一个connection
session.beginTransaction();
//session.save(s);
//session.delete(s);
session.update(s);
session.getTransaction().commit();
session.close();//关闭connection
sf.close();//关闭工厂相当于关闭了数据连接池
}
}
import org.hibernate.Session;
import org.hibernate.SessionFactory;
//import org.hibernate.cfg.AnnotationConfiguration;过时了,该类的所有内容都已经被包含在Configuration类中。
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
import com.test.hibernate.model.Teacher;
public class TeacherTest {
public static void main(String args[]){
Teacher t = new Teacher();
t.setId(2);
t.setName("t3");
t.setTitle("中级");
//Configuration cfg = new AnnotationConfiguration();
Configuration cfg = new Configuration();
//SessionFactory sf = cfg.configure().buildSessionFactory();
cfg.configure();//解析所有hibernate的配置xml,不指定参数就会去找默认目录下的xml
ServiceRegistry sr = new ServiceRegistryBuilder().applySettings(cfg.getProperties()).buildServiceRegistry();
SessionFactory sf = cfg.buildSessionFactory(sr);//生成session工厂,相当于产生数据库连connection的工厂
Session session = sf.openSession();//相当于数据库的一个connection
session.beginTransaction();
session.save(t);
session.getTransaction().commit();
session.close();//关闭connection
sf.close();//关闭工厂相当于关闭了数据连接池
}
}
class配置参考例子:
<class
name="ClassName"
table="tableName"
discriminator-value="discriminator_value"
mutable="true|false"
schema="owner"
catalog="catalog"
proxy="ProxyInterface"
dynamic-update="true|false"
dynamic-insert="true|false"
select-before-update="true|false"
polymorphism="implicit|explicit"
where="arbitrary sql where condition"
persister="PersisterClass"
batch-size="N"
optimistic-lock="none|version|dirty|all"
lazy="true|false"
entity-name="EntityName"
check="arbitrary sql check condition"
rowid="rowid"
subselect="SQL expression"
abstract="true|false"
node="element-name"
/>