初识Hibernate

Hibernate
典型的三层架构是表示层，业务层，持久层！Hibernate是持久层的框架，它的底层主要是对JDBC的封装。
下面是关于如何搭建一个Hibernate框架的步骤
配置Hibernate的步骤
1导包
将hibernate-release-4.3.11.Final\lib\required路径下的全部压缩包及所使用的数据库驱动包导入工程。
建立hibernate.cfg.xml文件，将该文件建在src根目录下；
2.1：拷一个配置模板：路径：
hibernate-release-4.3.11.Final/documentation/manual/en-US/html/ch01.html#tutorial-firstapp-configuration
示例:

<?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数据库连接 -->
    <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
    <property name="connection.url">jdbc:oracle:thin:@127.0.0.1:1521:XE</property>
    <property name="connection.username">HQ133</property>
    <property name="connection.password">HQ133</property>

    <!-- JDBC connection pool (use the built-in)JDBC 连接池：Hibernate内置的连接池 -->
    <property name="connection.pool_size">20</property>

    <!-- SQL dialect根据不同的数据库选择不同的方言 -->
    <property name="dialect">org.hibernate.dialect.Oracle10gDialect</property>

    <!-- Enable Hibernate's automatic session context management获取当前线程的Session对象 -->
    <property name="current_session_context_class">thread</property>

    <!-- Disable the second-level cache  -->
    <property name="cache.provider_class">org.hibernate.cache.internal.NoCacheProvider</property>

    <!-- Echo all executed SQL to stdout 执行hibernate过程中，将执行的sql语句显示到Console上 -->
    <property name="show_sql">true</property>

    <!-- Drop and re-create the database schema on startup  加载 对象与表的映射文件-->
    <property name="hbm2ddl.auto">update</property>
    <mapping resource="com/iotek/pojo/Student.hbm.xml"/>
  </session-factory>
</hibernate-configuration>

3创建一个Pojo包：建一个实体类（要实现Serializable接口）：

public class Student implements Serializable {

    private Long id;
    private String name; //attribute
    private String address;
    private String gender;
    private int  age;
    public Student(){}
    public Student(Long id, String name, String address, String gender, Integer age) {
        super();
        this.id = id;
        this.name = name;
        this.address = address;
        this.gender = gender;
        this.age = age;
    }
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    .............
此处有省略。。。。。。。。
   ..............
    public void setAge(Integer age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "Student [id=" + id + ", name=" + name + ", address=" + address + ", gender=" + gender + ", age=" + age
                + "]";
    }


}

4建立映射文件配置：userinfo.hbm.xml
模板位置：
hibernate-release-4.3.11.Final/documentation/manual/en-US/html/ch01.html#tutorial-firstapp-mapping
示例：

<?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="com.iotek.pojo">
<!-- name:代表索要映射的类名 table：代表索要映射的表名 -->
    <class name="Student" table="STUDENT">
        <!-- name:代表索要映射的类中id的属性名 table：代表索要映射的表ID列 -->
        <id name="id" column="ID" type="long">
<!--              <generator class="sequence">
                <param name="sequence">student_seq</param>
            </generator>  -->
        </id>

        <property name="name" type="string" column="NAME"/>
        <property name="address" type="string" column="ADDRESS"/>
        <property name="gender" type="string" column="GENDER"/>
        <property name="age" type="int" column="AGE"/>

    </class>


</hibernate-mapping>

5建立SessionFactory

package com.iotek.session;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;

public class HibernateSessionFactory {
    //static ThreadLocal<Session> local = new ThreadLocal<Session>();
    private static SessionFactory factory = null;
    private static Session session = null;

    static{
        //--Hibernate 3.X之前版本
        /*Configuration config = new Configuration();
        config.configure("hibernate.cfg.xml");
        factory = config.buildSessionFactory();*/

        //--Hibernate 3.X之后版本
        Configuration config = new Configuration();
        config.configure("hibernate.cfg.xml");
        ServiceRegistryBuilder builder = new ServiceRegistryBuilder();
        builder.applySettings(config.getProperties());
        ServiceRegistry service = builder.buildServiceRegistry();
        factory = config.buildSessionFactory(service);

    }

    private HibernateSessionFactory(){}

    public static Session getSession(){

        //--Session：第一种获得方式
        //session = factory.openSession();
        //--Session：第二种获得方式
        /*
        session = local.get();
        if(session==null){
            session = factory.openSession();
            local.set(session);
        }*/
        //--Session：第三种获得方式
        session = factory.getCurrentSession();
        return session;

    }

    public static void closeSession(){
        //--第一种优化方式的：关闭
        /*session = local.get();
        if(session!=null){
            if(session.isOpen()){
                session.close();
                local.set(null);
            }
        }*/

        if(session!=null){
            if(session.isOpen()){
                session.close();
            }
        }
    }

}

第六步：构建测试类：

public class Demo {

    public static void main(String[] args) {
        //--可以操作数据库的对象
        Session session = HibernateSessionFactory.getSession();
        /*
        Student stu = new Student("小明",55);
        //--创建操作Session的事务
        Transaction tran = null;
        //--开启session中的事务
        tran = session.beginTransaction();
        //--对数据的保存
        session.save(stu);


        //--提交事务
        tran.commit();*/
        Transaction tran = null;
        tran = session.beginTransaction();
        Student stu1 = (Student)session.get(Student.class, 2);
        tran.commit();
        System.out.println(stu1);

    //  HibernateSessionFactory.closeSession();

    }

}