Hibernate是一個開放源代碼的對象關系映射框架，可以應用在任何使用JDBC的場合，既可以在Java的客戶端程序實用，也可以在Servlet/JSP的Web應用中使用

優勢：
　　簡化開發，提高開發效率，持久層關系映射復雜情況下，hibernate開發效率相當高。
　　hibernate內部進行了JDBC的優化處理，以及增加緩存機制，大大提高了運行效率。
　　更好的移植性，Hibernate已經為我們屏蔽了數據庫之間的差異

　　Hibernate使用 Java 反射機制 而不是字節碼增強程序來實現透明性。
　　Hibernate的性能非常好，因為它是個輕量級框架。 映射的靈活性很出色。
　　Hibernate它支持各種關系數據庫，從一對一到多對多的各種復雜關系。

代碼結構

實體類User

public class User {
    
    private int id;
    private String name;
    private Date birthday;
    private int age;
    private int total;
    
    
    public User() {
        // TODO Auto-generated constructor stub
    }
    public User(String name, Date birthday, int age) {
        
 
super();
        this.name = name;
        this.birthday = birthday;
        this.age = 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 Date getBirthday() {
        return birthday;
    }
    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }
    public int getTotal() {
        return total;
    }
    public void setTotal(int total) {
        this.total = total;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    
}

orm映射文件User.hbm.xml

<?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>
  <class name="com.domain.User" table="user" catalog="ssh">
       <id name="id" column="id" type="int">
           <generator class="native"></generator>
       </id>
       <property name="name" column="name" type="java.lang.String"></property>
       <property name="age">
          <column name="age" sql-type="int"></column>
       </property>
       <property name="birthday" type="date"></property>
       <property name="total" formula="(select count(*) from user)"></property>
    </class>
</hibernate-mapping>

核心配置文件hibernate.cfg.xml

<?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="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql:///ssh</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.format_sql">true</property>
        <property name="hibernate.hbm2ddl.auto">update</property>
        <property name="javax.persistence.validation.mode">none</property>
        //這裏需要配置進來
        <mapping resource="com/domain/User.hbm.xml"/>
   </session-factory>
</hibernate-configuration>

HibernateUtils工具類

public class HibernateUtils {
    private static Configuration configuration;
    private static SessionFactory sessionFactory;

    static {
        configuration = new Configuration().configure();
        sessionFactory = configuration.buildSessionFactory();
    }

    public static Session openSession() {
        return sessionFactory.openSession();
    }
}

UserTest測試類

public class UserTest {
    
    //派生屬性
    @Test
    public void total(){
        Session session=HibernateUtils.openSession();
        Transaction transaction = session.beginTransaction();
        User user = (User) session.get(User.class, 6);
        System.out.println(user.getTotal());
        transaction.commit();
        session.close();
    }

    //刪除
    @Test
    public void delete(){
        Session session=HibernateUtils.openSession();
        Transaction transaction = session.beginTransaction();
        User user=new User();
        user.setId(3);
        session.delete(user);
        transaction.commit();
        session.close();
    }

//通過ID查詢
    @Test
    public void findById(){
        Session session=HibernateUtils.openSession();
        Transaction transaction = session.beginTransaction();
        User user=(User) session.get(User.class, 3);
        System.out.println(user);
        transaction.commit();
        session.close();
    }
//添加
    @Test
    public void add(){
        Session session = HibernateUtils.openSession();
        Transaction transaction = session.beginTransaction();
        for(int i=0;i<5;i++){
            User user=new User("cai"+i,new Date(),12+i);
            session.save(user);
        }
        transaction.commit();
        session.close();
    }

}

Hibernate快速入門