hibernate快速入门案例

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开发流程

1.创建一个项目

2.画出简单的项目框架图

3.引入hibernate开发包(http://www.hibernate.org)

hibernate开发方式的三种方式：

1由Domain object->mapping->db(官方推荐)

2由DB开始，用工具生成mapping和Domain object(使用较多)

3由映射文件开始

4.创建employe表

create table employee(
id int primary key,

name varchar(40) not null,

email varchar(40) not null,

hiredate date not null

)

5.开发domain对象和对象映射文件

在类路径src下新建包cn.java.domain,创建类Employee

package cn.java.domain;public class Employee implements java.io.Serializable{/**该domain对象按照规范序列化，目的是可以唯一的标识该对象，同时在网络和文件传输 *  */private static final long serialVersionUID = 1L;private Integer id;private String name;private String email;private java.util.Date hiredate;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 getEmail() {return email;}public void setEmail(String email) {this.email = email;}public java.util.Date getHiredate() {return hiredate;}public void setHiredate(java.util.Date hiredate) {this.hiredate = hiredate;}}

对象关系映射文件作用：作用是指定domain对象和表的映射关系，文件取名有规范：domain对象.hbm.xml。一般放在和domain对象同一文件下。

<?xml version="1.0" encoding="utf-8"?><!DOCTYPE hibernate-mapping PUBLIC         "-//Hibernate/Hibernate Mapping DTD 3.0//EN"        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping package="cn.java.domain"><class name="Employee" table="employee"><!-- id元素用于指定主键属性 --><id name="id" column="id" type="java.lang.Integer"><!-- 该元素用于指定主键生成策略 --><generator class="increment"/></id><!-- 对其他属性还有配置 --><property name="name" type="java.lang.String"><column name="name" not-null="false"></column></property><property  name="email" type="java.lang.String"><column name="email" not-null="false"/></property><property name="hiredate" type="java.util.Date"><column name="hiredate" not-null="false"/></property></class></hibernate-mapping>

6.手动配置我们的hibernate.cfg.xml文件，该文件用于配置链接的数据库的类型、driver、用户名、密码等。

<?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><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><property name="dialect">org.hibernate.dialect.MySQLDialect</property><property name="hbm2ddl.auto">update</property><property name="show_sql">true</property><mapping resource="cn/java/domain/Employee.hbm.xml"/></session-factory></hibernate-configuration>

7.手动测试

package cn.java.junit;import static org.junit.Assert.*;import java.util.Date;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction;import org.hibernate.cfg.Configuration;import cn.java.domain.Employee;import cn.java.utils.MySessionFactory;public class Test {@org.junit.Testpublic void test() {//1.创建Configuration,该对像用于读取hibernate.cfg.xml并完成初始化Configuration config =new Configuration().configure();//2.创建SessionFactory，这是一个会话工厂，是一个重量级的对象SessionFactory sf =config.buildSessionFactory();//3.创建Session相当于jdbc connnectionSession sess =sf.openSession();//4.对hibernate而言。要求程序员，在进行增加，删除，修改的时候要使用事务Transaction tx = sess.beginTransaction();//添加雇员Employee e=new Employee();e.setName("lb");e.setEmail("lb@163.com");e.setHiredate(new Date());sess.save(e); //==>insert into ...被hibernate封装tx.commit();sess.close();sf.close();}@org.junit.Testpublic void update(){

<span style="white-space:pre"></span>//修改用户Session session = MySessionFactory.getSessionFactory().openSession();Transaction ts =session.beginTransaction();//load方法通过主键属性获取实例对象

<span style="white-space:pre"></span>Employee e = session.load(Employee.class, 1);e.setName("xxx");ts.commit();session.close();}@org.junit.Testpublic void delete(){Session session = MySessionFactory.getSessionFactory().openSession();Transaction ts =session.beginTransaction();Employee e = session.load(Employee.class, 1);session.delete(e);ts.commit();session.close();}}

由于SessionFactory比较耗内存，我们可以把SessionFactory做成单例，创建一个工具类

package cn.java.utils;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;public class MySessionFactory {private static SessionFactory sf=null;    private MySessionFactory(){}public static SessionFactory getSessionFactory(){if(sf==null){sf = new Configuration().configure().buildSessionFactory();}return sf;}}

注：

<span style="white-space:pre"></span>Session session = MySessionFactory.getSessionFactory().openSession();Transaction ts =session.beginTransaction();Employee e = session.load(Employee.class, 1);e.setName("xxx");-->select * from employee where id =3;底层还是调用了sql语句ts.commit();session.close();

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