hibernate是一个ORM框架。
ORM的全拼是Object Relational Mapping，译为“对象关系映射”，是一种程序技术，用于实现面向对象编程语言里不同类型系统的数据之间的转换。从效果上来说，它其实是创建了一个可以在编程语言里使用的“虚拟对象数据库”。
使用较多的ORM框架有：
JPA---- Java Persistence API.JPA通过JDK 5.0注解或XML描述对象－关系表的映射关系（只有接口规范）Hibernate---- 最流行ORM框架，通过对象-关系映射配置，可以完全脱离底层SQLMyBatis---- ?本是apache的一个开源项目 iBatis，支持普通 SQL查询，存储过程和高级映射的优秀持久层框架Apache---- DBUtils Spring---- JDBCTemplate
接下来，我们通过一个案例演示hibernate的使用。先在项目中导入hibernate所需的一系列jar包：
接着，在源代码根路径下创建并配置hibernate.cfg.xml文件：
<?xml version=‘1.0‘ encoding=‘utf-8‘?><!DOCTYPE hibernate-configuration PUBLIC ???????"-//Hibernate/Hibernate Configuration DTD//EN" ???????"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"><hibernate-configuration> ???<session-factory> ???????<property name="connection.url">jdbc:mysql://localhost:3306/b0307</property> ???????<property name="connection.driver_class">com.mysql.jdbc.Driver</property> ???????<property name="connection.username">root</property> ???????<property name="connection.password">2018</property> ???????<property name="hibernate.show_sql">true</property> ???????<property name="hibernate.format_sql">true</property> ???????<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property> ???????<property name="hibernate.current_session_context_class">thread</property> ???????<mapping resource="com/itszt/domain/Emp.hbm.xml"></mapping> ???</session-factory></hibernate-configuration>
然后，映射数据库中的一个表，并据此创建映射的类Emp，并配置该类基于hibernate的配置文件Emp.hbm.xml：
package com.itszt.domain;/** * 测试用的实体类 */public class Emp { ???private int uid; ???private String name; ???public Emp(int uid, String name) { ???????this.uid = uid; ???????this.name = name; ???} ???@Override ???public String toString() { ???????return "Emp{" + ???????????????"uid=" + uid + ???????????????", name=‘" + name + ‘\‘‘ + ???????????????‘}‘; ???} ???public int getUid() { ???????return uid; ???} ???public void setUid(int uid) { ???????this.uid = uid; ???} ???public String getName() { ???????return name; ???} ???public void setName(String name) { ???????this.name = name; ???} ???public Emp() { ???}}Emp.hbm.xml配置文件：
<?xml version=‘1.0‘ encoding=‘utf-8‘?><!DOCTYPE hibernate-mapping PUBLIC ???????"-//Hibernate/Hibernate Mapping DTD 3.0//EN" ???????"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><hibernate-mapping package="com.itszt.domain"> ???<class name="Emp" table="emp"> ???????<id name="uid" column="uid"> ???????????<generator class="native"></generator> ???????</id> ???????<property name="name" column="name"></property> ???</class> ???<query name="queryTest1"> ???????SELECT new Emp(uid,name) FROM Emp WHERE uid=? order by uid desc ???</query> ???<query name="queryTest2"> ???????FROM Emp order by uid desc ???</query> ???<query name="queryTest3"> ???????<![CDATA[ ???????FROM Emp WHERE uid > ? and uid < ? ???????]]> ???</query></hibernate-mapping>
测试类：
import com.itszt.domain.Emp;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction;import org.hibernate.cfg.Configuration;/** * 测试类 */public class Test { ???public static void main(String[] args) { ???????Configuration configuration=new Configuration().configure("hibernate.cfg.xml"); ???????SessionFactory sessionFactory = configuration.buildSessionFactory(); ???????Session session = sessionFactory.openSession(); ???????Emp emp = new Emp(); ???????emp.setUid(2); ???????emp.setName("小马222"); ???????Transaction transaction = session.beginTransaction(); ???????//演示操作增删改查// ???????session.save(emp);// ???????session.delete(emp);// ???????session.update(emp); ???????Emp emp1 = (Emp) session.get(Emp.class, 2); ???????System.out.println("emp1 = " + emp1); ???????transaction.commit(); ???????session.close(); ???????sessionFactory.close(); ???}}此外，我们再创建一个工具类UtilHibernate，用来基于hibernate生成一个session：
import org.hibernate.HibernateException;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;/** * 工具类 */public class UtilHibernate { ???private static Configuration configuration; ???private static SessionFactory sessionFactory; ???//什么是要重复调用的 ???//什么是要初始加载一次的 ???static { ???????try { ???????????configuration=new Configuration().configure(); ???????????sessionFactory = configuration.buildSessionFactory(); ???????????//JVM的关闭钩子，在JVM退出时close我们的sessionFactory ???????????Runtime.getRuntime().addShutdownHook(new Thread(){ ???????????????@Override ???????????????public void run() { ???????????????????super.run(); ???????????????????System.out.println("Execute Hook....."); ???????????????????if (sessionFactory != null) { ???????????????????????sessionFactory.close(); ???????????????????} ???????????????} ???????????}); ???????} catch (HibernateException e) { ??????????throw ?new ExceptionInInitializerError("hibernate加载失败！！"); ???????} ???} ???public static Session openNew(){ ??????return sessionFactory.openSession(); ???} ???public static Session getCurrent(){ ???????return sessionFactory.getCurrentSession(); ???} ???public static void release(Session session){ ???????if (session != null) { ???????????if (session.isOpen()) { ???????????????session.close(); ???????????} ???????} ???}}接下来，通过该工具类，再分别通过query查询，hql，以及criteria来测试各自的用法：
TestQuery.javaimport com.itszt.domain.Emp;import org.hibernate.Session;import org.hibernate.Transaction;/** * 测试查询 */public class TestQuery { ???public static void main(String[] args) { ???????Session session1 = UtilHibernate.getCurrent(); ???????Transaction transaction = session1.beginTransaction(); ???????//饿加载:只要查询，马上就执行sql然后把结果取回 ???????Emp emp1= (Emp) session1.get(Emp.class, 2); ???????System.out.println("emp1 = " + emp1); ???????transaction.commit(); ???????UtilHibernate.release(session1); ???????Session session2 = UtilHibernate.getCurrent(); ???????Transaction transaction2 = session2.beginTransaction(); ???????//懒加载：等到使用该对象的时候再执行sql然后把结果取回 ???????Emp emp2= (Emp) session2.load(Emp.class, 2); ???????System.out.println("emp2 = " + emp2); ???????transaction2.commit(); ???????UtilHibernate.release(session2); ???????//退出JVM。。。 ???????System.exit(0); ???}}-----------------------------------------------------TestHQL.javaimport com.itszt.domain.Emp;import org.hibernate.Query;import org.hibernate.Session;import org.hibernate.Transaction;import java.util.Arrays;import java.util.List;/** * HQL查询语言 */public class TestHQL { ???//：role形式的参数设置查询 ???public static void main(String[] args) { ???????Session session = UtilHibernate.getCurrent(); ???????Transaction transaction = session.beginTransaction(); ???????Query query = session.createQuery("SELECT new Emp(uid,name) FROM Emp WHERE uid=:uid AND name=:name");// ???????query.setParameter("uid",8);// ???????query.setParameter("name","测试角色2222222"); ???????Emp emp=new Emp(2,"小马222"); ???????query.setProperties(emp); ???????Object result = query.uniqueResult(); ???????System.out.println("result = " + result); ???????transaction.commit(); ???????UtilHibernate.release(session); ???????System.exit(0); ???} ???public static void main4(String[] args) { ???????Session session = UtilHibernate.getCurrent(); ???????Transaction transaction = session.beginTransaction(); ???????Query query = session.createQuery("SELECT new Emp(uid,name) FROM Emp WHERE uid=?"); ???????query.setParameter(0,2); ???????Emp emp= (Emp) query.uniqueResult(); ???????System.out.println("emp = " + emp); ???????transaction.commit(); ???????UtilHibernate.release(session); ???????System.exit(0); ???} ???//查询其中的几列 ???public static void main3(String[] args) { ???????Session session = UtilHibernate.getCurrent(); ???????Transaction transaction = session.beginTransaction(); ???????Query query = session.createQuery("SELECT uid,name FROM Emp WHERE uid=?"); ???????query.setParameter(0,2); ???????Object[] results= (Object[]) query.uniqueResult(); ???????System.out.println("results = " + Arrays.toString(results)); ???????Query query1 = session.createQuery("SELECT COUNT (*) FROM Emp"); ???????Long num = (Long) query1.uniqueResult(); ???????System.out.println("num = " + num); ???????transaction.commit(); ???????UtilHibernate.release(session); ???????System.exit(0); ???} ???//查询单个数据，设置查询条件，返回单个对象 ???public static void main2(String[] args) { ???????Session session = UtilHibernate.getCurrent(); ???????Transaction transaction = session.beginTransaction(); ???????Query query = session.createQuery("FROM Emp WHERE uid=?"); ???????query.setParameter(0,2); ???????Emp emp= (Emp) query.uniqueResult(); ???????System.out.println("emp = " + emp); ???????transaction.commit(); ???????UtilHibernate.release(session); ???????System.exit(0); ???} ???//查询全部数据 ，返回一个list ???public static void main1(String[] args) { ???????Session session = UtilHibernate.getCurrent(); ???????Transaction transaction = session.beginTransaction(); ???????Query query = session.createQuery("FROM Emp"); ???????List<Emp> list = query.list(); ???????System.out.println("list = " + list); ???????transaction.commit(); ???????UtilHibernate.release(session); ???????System.exit(0); ???}}--------------------------------------------TestHQL2.javaimport com.itszt.domain.Emp;import org.hibernate.Query;import org.hibernate.SQLQuery;import org.hibernate.Session;import org.hibernate.Transaction;import java.util.Arrays;import java.util.List;/** * HQL查询语言2 */@SuppressWarnings("ALL")public class TestHQL2 { ???//原生SQL查询 ???public static void main(String[] args) { ???????Session session = UtilHibernate.getCurrent(); ???????Transaction transaction = session.beginTransaction(); ???????SQLQuery sqlQuery = session.createSQLQuery("SELECT * FROM emp"); ???????sqlQuery.addEntity(Emp.class); ???????List<Emp> emp = (List<Emp>) sqlQuery.list(); ???????System.out.println("emp = " + emp); ???????transaction.commit(); ???????UtilHibernate.release(session); ???????System.exit(0); ???} ???//原生SQL查询 ???public static void main2(String[] args) { ???????Session session = UtilHibernate.getCurrent(); ???????Transaction transaction = session.beginTransaction(); ???????SQLQuery sqlQuery = session.createSQLQuery("SELECT * FROM emp"); ???????List<Object[]> list = sqlQuery.list(); ???????for (Object[] o : list) { ???????????System.out.println("o = " + Arrays.toString(o)); ???????} ???????transaction.commit(); ???????UtilHibernate.release(session); ???????System.exit(0); ???} ???//将SQL写在配置文件里 ???public static void main1(String[] args) { ???????Session session = UtilHibernate.getCurrent(); ???????Transaction transaction = session.beginTransaction(); ???????Query query = session.getNamedQuery("queryTest1"); ???????query.setParameter(0,8); ???????Emp emp= (Emp) query.uniqueResult(); ???????System.out.println("emp = " + emp); ???????Query queryTest2 = session.getNamedQuery("queryTest2"); ???????List list = queryTest2.list(); ???????System.out.println("list = " + list); ???????Query queryTest3 = session.getNamedQuery("queryTest3"); ???????queryTest3.setParameter(0,2); ???????queryTest3.setParameter(1,6); ???????List list2 = queryTest3.list(); ???????System.out.println("list2 = " + list2); ???????transaction.commit(); ???????UtilHibernate.release(session); ???????System.exit(0); ???}}------------------------------------------------------TestCriteria.javaimport com.itszt.domain.Emp;import org.hibernate.Criteria;import org.hibernate.Session;import org.hibernate.Transaction;import org.hibernate.criterion.Projections;import org.hibernate.criterion.Restrictions;import java.util.List;/** * 测试Criteria方式 */public class TestCriteria { ???public static void main(String[] args) { ???????Session session = UtilHibernate.getCurrent(); ???????Transaction transaction = session.beginTransaction(); ???????Criteria criteria = session.createCriteria(Emp.class); ???????//基本比较 ???????//criteria.add(Restrictions.lt("uid",5));// ???????criteria.add(Restrictions.lt("uid",3));// ???????criteria.add(Restrictions.gt("uid",1)); ???????//分页--------- ???????criteria.setFirstResult(0); ???????criteria.setMaxResults(5); ???????//分页--------- ???????List<Emp> emps= criteria.list(); ???????System.out.println("emps = " + emps); ???????//聚合 ???????/*criteria.setProjection(Projections.sum("uid")); ???????Long result= (Long) criteria.uniqueResult(); ???????System.out.println("result = " + result);*/ ???????transaction.commit(); ???????UtilHibernate.release(session); ???????System.exit(0); ???} ???public static void main1(String[] args) { ???????Session session = UtilHibernate.getCurrent(); ???????Transaction transaction = session.beginTransaction(); ???????Criteria criteria = session.createCriteria(Emp.class); ???????criteria.add(Restrictions.eq("uid",6)); ???????Emp emp = (Emp) criteria.uniqueResult(); ???????System.out.println("emp = " + emp); ???????transaction.commit(); ???????UtilHibernate.release(session); ???????System.exit(0); ???}} hibernate使用
原文地址：https://www.cnblogs.com/lizhangyong/p/8822996.html