Hibernate快速入门

Posted 2020-10-19 weishao-lsv

Hibernate是一个开放源代码的对象关系映射框架，可以应用在任何使用JDBC的场合，既可以在Java的客户端程序实用，也可以在Servlet/JSP的Web应用中使用

优势：
　　简化开发，提高开发效率，持久层关系映射复杂情况下，hibernate开发效率相当高。
　　hibernate内部进行了JDBC的优化处理，以及增加缓存机制，大大提高了运行效率。
　　更好的移植性，Hibernate已经为我们屏蔽了数据库之间的差异

　　Hibernate使用 Java 反射机制 而不是字节码增强程序来实现透明性。
　　Hibernate的性能非常好，因为它是个轻量级框架。 映射的灵活性很出色。
　　Hibernate它支持各种关系数据库，从一对一到多对多的各种复杂关系。

 

代码结构

 

 

实体类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>
        //这里需要配置进来
        <mapping resource="com/domain/User.hbm.xml"/>
   </session-factory>
</hibernate-configuration>

 

HibernateUtils工具类

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测试类

public class UserTest {
    
    //派生属性
    @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();
    }

    //删除
    @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();
    }

//通过ID查询
    @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();
    }

}