hibernate注解初探

1.对项目引入注解所需的jar包，本例使用的是hibernate-annotations-3.4.0.，包括注解核心包以及注解必需的包（其它的hibernate所需的jar包已经引入项目，详见hibernate初探，使用的是hibernate-3.3.2）

2.在数据库新建测试表teacher（项目使用的是oracle数据库）

-- Create tablecreate table TEACHER(  id    NUMBER not null,  name  VARCHAR2(20),  title VARCHAR2(20))tablespace USERS  pctfree 10  initrans 1  maxtrans 255  storage  (    initial 64    minextents 1    maxextents unlimited  );-- Create/Recreate primary, unique and foreign key constraints alter table TEACHER  add constraint PPP primary key (ID)  using index   tablespace USERS  pctfree 10  initrans 2  maxtrans 255  storage  (    initial 64K    minextents 1    maxextents unlimited  );

3.新建实体类Teacher，并加入注解@Entity和@Id，分别位于类名上面和主键的get方法上面

package com.baosight.model;import javax.persistence.Entity;import javax.persistence.Id;/** * <p>Title: </p> * <p>Description:Student </p> * <p>Company: </p>  * @author yuan  * @date 2016-4-10 下午12:32:46*/@Entitypublic class Teacher {private int id;private String name;private String title;@Idpublic 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 String getTitle() {return title;}public void setTitle(String title) {this.title = title;}}

4.修改hibernate配置文件，加入Teacher的配置信息，本例中为：<mapping class="com.baosight.model.Teacher"/>

<?xml version='1.0' encoding='utf-8'?><!DOCTYPE hibernate-configuration PUBLIC        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"><hibernate-configuration>    <session-factory>        <!-- Database connection settings -->        <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>        <property name="connection.url">jdbc:oracle:thin:@127.0.0.1:1521:orcl</property>        <property name="connection.username">scott</property>        <property name="connection.password">tiger</property>        <!-- JDBC connection pool (use the built-in) -->        <!-- <property name="connection.pool_size">1</property> -->        <!-- SQL dialect -->        <property name="dialect">org.hibernate.dialect.Oracle9Dialect</property>        <!-- Enable Hibernate's automatic session context management -->       <!--  <property name="current_session_context_class">thread</property> -->        <!-- Disable the second-level cache  -->        <property name="cache.provider_class">org.hibernate.cache.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">update</property>        <mapping resource="com/baosight/model/Student.hbm.xml"/><mapping class="com.baosight.model.Teacher"/>    </session-factory></hibernate-configuration>

5.新建测试类TestTeacher测试新增数据

import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.cfg.AnnotationConfiguration;import org.hibernate.cfg.Configuration;import com.baosight.model.Student;import com.baosight.model.Teacher;/** * <p>Title: </p> * <p>Description:TestStu </p> * <p>Company: </p>  * @author yuan  * @date 2016-4-10 下午3:16:01*/public class TestTecher {/**  * @Title: main  * @Description: TODO * @param args  * @return void   * @throws  */public static void main(String[] args) {// TODO Auto-generated method stub//教师测试类Teacher t = new Teacher();t.setId(1);t.setName("t1");t.setTitle("中级");//读取配置文件Configuration cfg = new AnnotationConfiguration();//得到session工厂SessionFactory sf = cfg.configure().buildSessionFactory();//得到sessionSession session = sf.openSession();//开启事务session.beginTransaction();//session执行savesession.save(t);//事务提交session.getTransaction().commit();//关闭sessionsession.close();//关闭session工厂sf.close();}}

6.运行TestTeacher，查询数据库，记录成功添加

结果：1 1 t1 中级
综上所述，注解与常规的方法相比，代码要简洁许多，注解存在于实体类中，不需要再有实体类和对应数据库表的映射文件了，只需在hibernate配置文件中声明一下实体类的映射就行了，另外，注意使用注解读取hibernate配置文件时使用的是AnnotationConfiguration类，而不是普通的Configuration类。