hibernate的对象与数据库表的映射

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风吹过的烟花 2022-09-07 16:41:46 博主文章分类：Java ©著作权

文章标签 hibernate sql xml 文章分类 运维

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Customer.java

/**
 * 客户管理的实体类
 * @author zhang
 *CREATE TABLE `cst_customer` (
  `cust_id` bigint(32) NOT NULL AUTO_INCREMENT COMMENT '客户编号(主键)',
  `cust_name` varchar(32) NOT NULL COMMENT '客户名称(公司名称)',
  `cust_source` varchar(32) DEFAULT NULL COMMENT '客户信息来源',
  `cust_industry` varchar(32) DEFAULT NULL COMMENT '客户所属行业',
  `cust_level` varchar(32) DEFAULT NULL COMMENT '客户级别',
  `cust_phone` varchar(64) DEFAULT NULL COMMENT '固定电话',
  `cust_mobile` varchar(16) DEFAULT NULL COMMENT '移动电话',
  PRIMARY KEY (`cust_id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
 */

public class Customer {
  private Long cust_id;
  private String cust_name;
  private String cust_source;
  private String cust_industry;
  private String cust_level;
  private String cust_phone;
  private String cust_mobile;
    //-----省略了get和set方法
}

Customer.hbm.xml----------建议和类放在一起

<?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>
    <!-- 建立类与表的映射 -->
    <!-- 类的全路径 -->
    <class name="com.hibernate.demo1.Customer" table="cst_customer">
        <!-- 建立类中的属性与表中的主键对应 -->
        <id name="cust_id" column="cust_id">
            <!-- 主键生成策略 -->
            <!-- native increment identity -->
            <generator class="native"/>
        </id>
        
        <!-- 建立类中的普通的属性和表的字段的对应 -->
        <property name="cust_name" column="cust_name"/>
        <property name="cust_source" column="cust_source"/>
        <property name="cust_industry" column="cust_industry"/>
        <property name="cust_level" column="cust_level"/>
        <property name="cust_phone" column="cust_phone"/>
        <property name="cust_mobile" column="cust_mobile"/>
    </class>
</hibernate-mapping>

hibernate.cfg.xml-------------要放在项目的src下

<?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>
    <!-- 连接数据库的基本参数 -->
    <!-- hibernate-release-5.0.7.Final\project\etc\hibernate.properties -->
    <!-- localhost:3306 -->
    <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
    <property name="hibernate.connection.url">jdbc:mysql:///hibernate_day02</property>
    <property name="hibernate.connection.username">root</property>
    <property name="hibernate.connection.password">password</property>
    <!-- 配置Hibernate的方言 -->
    <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
    
    <!-- ==========可选配置========= -->
    <!-- 打印sql -->
    <property name="hibernate.show_sql">true</property>
    <!-- 格式化sql -->
    <property name="hibernate.format_sql">true</property>
    <!-- 自动创建表 -->
    <property name="hibernate.hbm2ddl.auto">create</property>
    
    <!-- 设置事务隔离级别 -->
    <!-- 
      1 read uncommitted  :脏读、不可重复读、虚读都会发生
      2 read committed    :解决脏读  (oracle默认)
      4 repeatable read   :解决脏读和不可重复读(mysql默认)
      8 serializable      :解决所有问题。串行执行、效率低
     -->
    <property name="hibernate.connection.isolation">4</property>
    <!-- 配置当前线程绑定的Session -->
    <!-- 不用session.close() -->
    <property name="hibernate.current_session_context_class">thread</property>
    
        <!-- 与表映射的类的全路径，把.换成/ -->
    <mapping resource="com/hibernate/demo1/Customer.hbm.xml"/>
  </session-factory>
</hibernate-configuration>

HibernateDemo1.java

/**
 * hibernate的入门案例
 *
 */
public class HibernateDemo1 {
  
  @Test
  //保存客户的案例
  public void demo1() {
    //1.加载Hibernate的核心配置文件
    Configuration configuration=new Configuration().configure();
    //2.创建一个SessionFactory对象：类似于JDBC连接池
    SessionFactory sessionFactory=configuration.buildSessionFactory();
    //3.通过SessionFactory获取Session对象：类似于JDBC的Connection
    Session session=sessionFactory.openSession();
    //4.手动开启事务
    Transaction transaction= session.beginTransaction();
    //5.编写代码
    
    Customer customer=new Customer();
    customer.setCust_name("王东");
    
    session.save(customer);
    
    //6.事务提交
    transaction.commit();
    //7.资源释放
    session.close();
    sessionFactory.close();
  }
}

简单的增删改查

HibernateDemo2.java

/**
 * hibernate的入门案例
 *
 */
public class HibernateDemo2 {
  
  @Test
  //保存客户的案例
  public void demo1() {
    //1.加载Hibernate的核心配置文件
    Configuration configuration=new Configuration().configure();
    //2.创建一个SessionFactory对象：类似于JDBC连接池
    SessionFactory sessionFactory=configuration.buildSessionFactory();
    //3.通过SessionFactory获取Session对象：类似于JDBC的Connection
    Session session=sessionFactory.openSession();//非线程安全，所以不能放在全局变量
    //4.手动开启事务
    Transaction transaction= session.beginTransaction();
    //5.编写代码
    
    Customer customer=new Customer();
    customer.setCust_name("王二");
    
    session.save(customer);
    
    //6.事务提交
    transaction.commit();
    //7.资源释放
    session.close();
    sessionFactory.close();
  }
  
  @Test
  //查询
  /**
   * get和load的区别
   */
  public void demo2() {
    Configuration configuration=new Configuration().configure();
    SessionFactory sessionFactory=configuration.buildSessionFactory();
    Session session=sessionFactory.openSession();
    Transaction tx=session.beginTransaction();
    
    /**
     * get
     * 立即加载，执行到这行代码，马上去查询
     * 查询后返回是真实对象本身
     * 查询找不到，返回null
     * 
     * load
     * 延迟加载(lazy懒加载)，执行到这行代码不会发送sql语句，当使用这个对象的时候才会发送sql语句
     * 查询后返回的是代理对象，javassist-3.18.1-GA.jar
     * 查询找不到，返回ObjectNotFoundException
     */
    
    //使用get方法查询
//    Customer customer=session.get(Customer.class, 1L);//发送sql语句
//    System.out.println(customer);
    
    //使用load方法查询
    Customer customer=session.load(Customer.class, 2L);
    System.out.println(customer);
    
    tx.commit();
    session.close();
  }
  
  @Test
  //修改操作
  public void demo3() {
    Configuration configuration=new Configuration().configure();
    SessionFactory sessionFactory=configuration.buildSessionFactory();
    Session session=sessionFactory.openSession();
    Transaction tx=session.beginTransaction();
    
    //直接创建对象，进行修改
//    Customer customer=new Customer();
//    customer.setCust_id(1L);
//    customer.setCust_name("王聪");
//    session.update(customer);
    //先查询，再修改（推荐）
    Customer customer=session.get(Customer.class, 1L);
    customer.setCust_name("王小贱");
    session.update(customer);
    
    tx.commit();
    session.close();
  }
  
  @Test
  //删除操作
  public void demo4() {
    Configuration configuration=new Configuration().configure();
    SessionFactory sessionFactory=configuration.buildSessionFactory();
    Session session=sessionFactory.openSession();
    Transaction tx=session.beginTransaction();
    
    //直接创建对象，删除
//    Customer customer=session.get(Customer.class, 1L);
//    customer.setCust_id(1L);
//    session.delete(customer);
    //先查询，在删除(推荐)------
    Customer customer=session.get(Customer.class, 2L);
    session.delete(customer);
    
    tx.commit();
    session.close();
  }
  
  @Test
  //保存或更新
  public void demo5() {
    Configuration configuration=new Configuration().configure();
    SessionFactory sessionFactory=configuration.buildSessionFactory();
    Session session=sessionFactory.openSession();
    Transaction tx=session.beginTransaction();
    
//    Customer customer=new Customer();
//    customer.setCust_name("汪峰");
//    session.saveOrUpdate(customer);
    
    Customer customer=new Customer();
    customer.setCust_id(3L);
    customer.setCust_name("李凤");
    session.saveOrUpdate(customer);
    
    tx.commit();
    session.close();
  }
  
  @Test
  //查询所有
  public void demo6() {
    Configuration configuration=new Configuration().configure();
    SessionFactory sessionFactory=configuration.buildSessionFactory();
    Session session=sessionFactory.openSession();
    Transaction tx=session.beginTransaction();
    //接收HQL：Hibernate Query Language 面向对象的查询语言
//    Query query= session.createQuery("from Customer");
//    List<Customer> list=query.list();
//    for (Customer customer : list) {
//      System.out.println(customer);
//    }
    
    //接收sql
    SQLQuery query=session.createSQLQuery("select * from cst_customer");
    List<Object[]> list=query.list();
    for (Object[] objects : list) {
      System.out.println(Arrays.toString(objects));
    }
    
    tx.commit();
    session.close();
  }
}

获取session的一个工具类

HibernateUtils.java

/**
 * Hibernate的工具类
 *
 */
public class HibernateUtils {

  public static final Configuration cfg;
  public static final SessionFactory sf;
  
  static{
    cfg = new Configuration().configure();
    sf = cfg.buildSessionFactory();
  }
  
  public static Session openSession(){
    return sf.openSession();
  }
  
  public static Session getCurrentSession() {
    return sf.getCurrentSession();//需要配置
  }
}