创建一个实体类：
package domain;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_linkman; ???private String cust_phone; ???private String cust_mobile; ???public Long getCust_id() { ???????return cust_id; ???} ???public void setCust_id(Long cust_id) { ???????this.cust_id = cust_id; ???} ???public String getCust_name() { ???????return cust_name; ???} ???public void setCust_name(String cust_name) { ???????this.cust_name = cust_name; ???} ???public String getCust_source() { ???????return cust_source; ???} ???public void setCust_source(String cust_source) { ???????this.cust_source = cust_source; ???} ???public String getCust_industry() { ???????return cust_industry; ???} ???public void setCust_industry(String cust_industry) { ???????this.cust_industry = cust_industry; ???} ???public String getCust_level() { ???????return cust_level; ???} ???public void setCust_level(String cust_level) { ???????this.cust_level = cust_level; ???} ???public String getCust_linkman() { ???????return cust_linkman; ???} ???public void setCust_linkman(String cust_linkman) { ???????this.cust_linkman = cust_linkman; ???} ???public String getCust_phone() { ???????return cust_phone; ???} ???public void setCust_phone(String cust_phone) { ???????this.cust_phone = cust_phone; ???} ???public String getCust_mobile() { ???????return cust_mobile; ???} ???public void setCust_mobile(String cust_mobile) { ???????this.cust_mobile = cust_mobile; ???} ???@Override ???public String toString() { ???????return "Customer [cust_id=" + cust_id + ", cust_name=" + cust_name + "]"; ???}}ORM元数据配置文件：
<?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"> ??<!-- 配置表与实体对象的关系 --><hibernate-mapping> ???<class name="domain.Customer" table="cst_customer" > ???????<id name="cust_id" ?> ???????????<!-- generator:主键生成策略 --> ???????????<generator class="native"></generator> ???????</id> ???????<property name="cust_name" column="cust_name" ></property> ???????<property name="cust_source" column="cust_source" ></property> ???????<property name="cust_industry" column="cust_industry" ></property> ???????<property name="cust_level" column="cust_level" ></property> ???????<property name="cust_linkman" column="cust_linkman" ></property> ???????<property name="cust_phone" column="cust_phone" ></property> ???????<property name="cust_mobile" column="cust_mobile" ></property> ???</class></hibernate-mapping>
这里的主键生成策略是native
详细：
主键生成策略.就是每条记录录入时,主键的生成规则.(7个)
identity : 主键自增。由数据库来维护主键值。录入时不需要指定主键。
sequence: Oracle中的主键生成策略，这里使用的是MySQL，暂时不介绍
increment(不使用，存在效率低和线程安全问题): 主键自增.由hibernate来维护.每次插入前会先查询表中id最大值.+1作为新主键值.
hilo(不使用，了解即可)：高低位算法，主键自增。由hibernate来维护，开发时不使用。
native：hilo+sequence+identity 自动三选一策略（检测当前数据库，使用相应的策略）
uuid： 产生理论上永远不会重复的随机字符串作为主键. 主键类型必须为string 类型.
assigned：自然主键生成策略。hibernate不会管理主键值，由开发人员自己录入。
hibernate对象分为三种状态：
瞬时状态：没有id，没有session关联
持久化状态：有id，与session关联
游离状态（托管状态）：有id，没有与session关联
package state;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction;import org.hibernate.cfg.Configuration;import org.junit.Test;import cn.itheima.domain.Customer;import cn.itheima.utils.HibernateUtils;//测试对象的三种状态public class Demo { ???@Test ???//查看三种状态 ???public void fun1(){ ???????//1 获得session ???????Session session = HibernateUtils.openSession(); ???????//2 控制事务 ???????Transaction tx = session.beginTransaction(); ???????//3执行操作 ???????Customer c = new Customer(); // 没有id, 没有与session关联 => 瞬时状态 ???????????????c.setCust_name("联想"); // 瞬时状态 ???????????????session.save(c); // 持久化状态, 有id,有关联 ???????????????//4提交事务.关闭资源 ???????tx.commit(); ???????session.close();// 游离|托管 状态, 有id , 没有关联 ???????????????????} ???????@Test ???//三种状态特点 ???//save方法: 其实不能理解成保存.理解成将瞬时状态转换成持久状态的方法 ???//主键自增 : 执行save方法时,为了将对象转换为持久化状态.必须生成id值.所以需要执行insert语句生成. ???//如果主键生成策略是increment: 执行save方法,为了生成id.会执行查询id最大值的sql语句（select max(id) from 表）. ???public void fun2(){ ???????//1 获得session ???????Session session = HibernateUtils.openSession(); ???????//2 控制事务 ???????Transaction tx = session.beginTransaction(); ???????//3执行操作 ???????Customer c = new Customer(); // 没有id, 没有与session关联 => 瞬时状态 ???????????????c.setCust_name("联想"); // 瞬时状态 ???????????????session.save(c); // 持久化状态, 有id,有关联 ???????????????//4提交事务.关闭资源 ???????tx.commit(); ???????session.close();// 游离|托管 状态, 有id , 没有关联 ???????????????????} ???????@Test ???//三种状态特点 ???// 持久化状态特点: 持久化状态对象的任何变化都会自动同步到数据库中. ???public void fun3(){ ???????//1 获得session ???????Session session = HibernateUtils.openSession(); ???????//2 控制事务 ???????Transaction tx = session.beginTransaction(); ???????//3执行操作 ???????????????Customer c = session.get(Customer.class, 1l);//持久化状态对象 ???????????????c.setCust_name("微软公司"); ???????????????//4提交事务.关闭资源 ???????tx.commit(); ???????session.close();// 游离|托管 状态, 有id , 没有关联 ???????????????????}}接下来从状态角度分析hibernate的增删改查：
hibernate框架学习笔记4：主键生成策略、对象状态
原文地址：https://www.cnblogs.com/xuyiqing/p/8449059.html