1.hibernate基础

百科定义：

hibernate是java语言下的对象关系映射解决方案

同类产品：

ibatis:半ORM产品，可以直接写sql
mybatis：这是ibatis的升级版
springJDBC: 这是spring提供的持久层技术

hibernate和mybatis各有各的方式，hibernate封装比较完整，完全是面向对象方式操作数据库，而mybatis是可以写sql的，在大多数互联网应用中，使用mybatis比较多，但是hibernate还是要学习的

安装配置

配置文件

<!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
    <session-factory>
<!--        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://127.0.0.1/test"</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">root</property>
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
        
        <mapping resource="entity/User.hbm.xml" /> -->
        
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://127.0.0.1/test</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">root</property>
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
        <property name="hibernate.show_sql">true</property>
        <property name="hibernate.hbm2ddl.auto">update</property>
        
        <mapping resource="entity/User.hbm.xml"/>       
        
    </session-factory>
</hibernate-configuration>

sessionFactory工具类（单例模式）

    package util;
    
    import org.hibernate.SessionFactory;
    import org.hibernate.cfg.Configuration;
    import org.hibernate.classic.Session;
    
    public class hibernateUtil {
        private static SessionFactory factory;
        
        static{
            try{
                //读取配置文件hibernate.cfg.xml
                //这里最后的函数configure，如果不加的话，是读取.propertys文件
                Configuration cfg = new Configuration().configure();
                factory = cfg.buildSessionFactory();
            }catch(Exception e){
                e.printStackTrace();
            }       
        }
        
        public static Session getSession()
        {
            return factory.openSession();
        }
        
        public static void closeSession(Session session)
        {
            if(session!=null)
            {
                if(session.isOpen())
                {
                    session.close();
                }
            }
        }
        
        public static SessionFactory getSessionFactory()
        {
            return factory;
        }
    }

实体类：

    package entity;
    
    public class User {
        private int id;
        private String userName;
        private String passWd;
        
        public User(){}
    
        public int getId() {
            return id;
        }
    
        public void setId(int id) {
            this.id = id;
        }
    
        public String getUserName() {
            return userName;
        }
    
        public void setUserName(String userName) {
            this.userName = userName;
        }
    
        public String getPassWd() {
            return passWd;
        }
    
        public void setPassWd(String passWd) {
            this.passWd = passWd;
        }
        
        
    }

映射文件：

    <?xml version="1.0"?>
    <!DOCTYPE hibernate-mapping PUBLIC 
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
    <hibernate-mapping>
        <class name="entity.User">
            <id name="id">
                <generator class="native"/>
            </id>
            <property name="userName" />        
            <property name="passWd" />
        </class>    
    </hibernate-mapping>

建表代码：

    package util;
    import org.hibernate.cfg.Configuration;
    import org.hibernate.tool.hbm2ddl.SchemaExport;
    
    
    public class ExportDb {
        public static void main(String[] args) {
            //读取配置文件
            Configuration cfg = new Configuration().configure();
            
            SchemaExport export = new SchemaExport(cfg);
            //自动生成对应的表
            export.create(true, true);
        }
    }