Hibernate入门教程

Hibernate

随心所欲的使用面向对象思想操纵数据库.

介绍
搭建开发环境
半sql半面向对象写法
完全的sql写法
完全的面向对象写法

Hibernate

Hibernate是一个开放源代码的对象关系映射框架，它对JDBC进行了非常轻量级的对象封装，它将POJO与数据库表建立映射关系，hibernate可以自动生成SQL语句，自动执行，使得Java程序员可以随心所欲的使用对象编程思维来操纵数据库,从而无需顾及数据库的实现究竟是SQLServer还是Mysql还是Oracle

搭建环境

搭建在一般工程中

jar下载
配置文件

jar下载

官网Hibernate进入后看到hibenate ORM,点击more,左侧边栏选择releases中的一个版本,页面最下方,选择download下载即可

官方jar包:lib文件:requeired文件里的所有jar拷贝到自己的新建工程中去,然后在加上连接数据库相关的包,mysql-connector

配置文件

Hibernate.cfg.xml放置在src下,需要修改url,username和password

	<?xmlversion='1.0'encoding='utf-8'?>

	<!DOCTYPEhibernate-configurationPUBLIC

	"-//Hibernate/HibernateConfigurationDTD//EN"

	"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

	<hibernate-configuration>

	<session-factory>

	<propertyname="connection.url">jdbc:mysql://localhost:3306/mycms</property>

	<propertyname="connection.driver_class">com.mysql.jdbc.Driver</property>

	<propertyname="connection.username">root</property>

	<propertyname="connection.password">123456</property>

	<mappingresource="com/selton/Node.hbm.xml"></mapping>

	</session-factory>

	</hibernate-configuration>

<mappingresource="com/selton/Node.hbm.xml"></mapping>

Node.hbm.xml 映射到具体的pojo,一个pojo配置一个映射的xml

名字和数据库的名字即使一样,也需要写上property的映射

	<?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.selton">

	<class name="com.selton.Node" table="tree">

	    <id name="id" column="id">

	        <generator class="native"></generator>

	        <!--可以实现自动增长,也就是将实体类存储到数据库的时候,少set一个主键

	           比较疑惑,反正有没有这句话,数据库那儿都需要自动增长-->

	    </id>

	    <property name="nodeId" column="nodeId"></property>

	    <property name="pid" column="pid"></property>

	    <property name="type" column="type"></property>

	    <property name="url" column="url"></property>

	    <property name="icon" column="icon"></property>

	    <property name="description" column="description"></property>

	    <property name="level" column="level"></property>

	    <property name="name" column="name"></property>

	</class>

	</hibernate-mapping>

pojo的主键属性名称对应到数据库实体的主键名称写在id中

,其他的写在property中

在一个入口方法或者测试类方法中,加入

//构建上下文换肩加配置连接池,开启事务

Configuration configuration = new Configuration().configure();

SessionFactory sessionFactory = configuration.buildSessionFactory();

Session session = sessionFactory.openSession();

Transaction transaction = session.beginTransaction();

//这里填写测试代码

//提交事务并关闭各种流

transaction.commit();

session.close();

sessionFactory.close();

以下的测试代码,分别放在上面代码的``这里填写测试代码`处

单个数据存储到数据库

	Node node = new Node();;

	node.setNodeId("testNodeId1");

	node.setPid("testPid1");

	node.setType((byte)1);

	node.setLevel((short)1);

	node.setName("testName1");

	session.save(node);

查询单个对象

Node node=(Node)session.get(Node.class,1);

System.out.println(node);

//Node.class后面的1是数据库中的主键值

更新单个对象

Node node=(Node)session.get(Node.class,10);

node.setName("updateName");

session.update(node);

删除对象

Node node = (Node) session.get(Node.class, 10);

session.delete(node);

查询整个表

这里需要注意,如果你的pojo叫 myuser,而数据库中对应的表叫user,所有使用createQuery的地方,涉及到了表,就该填myuser

Query query = session.createQuery("FROM Node");

List list = query.list();

System.out.println("list = " + list);

查询某个对象的某个属性

Query query = session.createQuery("SELECT nodeId FROM Node");

List list = query.list();

System.out.println("list = " + list);

查询指定行数据

Query query = session.createQuery("FROM Node WHERE type=?");

query.setParameter(0,10);

List list = query.list();

System.out.println("list = " + list);

查询指定数据传回一个实体

//需要pojo有相应的构造器

Query query = session.createQuery("SELECT new Node(id,name,nodeId) FROM Node");

List<Node> list = query.list();

System.out.println("list = " + list);

分组聚合

Query query = session.createQuery("SELECT type,SUM(id) FROM Node GROUP BY type");

List list = query.list();

for (Object o : list) {

    Object[] result = (Object[]) o;

    System.out.println(Arrays.toString(result));

}

排序

Query query = session.createQuery("FROM Node ORDER BY id DESC");

List list = query.list();

System.out.println("list = " + list);

limit

Query query = session.createQuery("FROM Node ORDER BY id DESC");

query.setFirstResult(2);

query.setMaxResults(3);

List list = query.list();

System.out.println("list = " + list);

使用参数

String colName = "id";

String sql = "FROM Node WHERE " + colName + "=?";

Query query = session.createQuery(sql);

query.setParameter(0,6);

Node node = (Node) query.uniqueResult();

System.out.println("node = " + node);

或者这种

Query query = session.createQuery("FROM Node WHERE id:id");

query.setParameter("id",7);

List list = query.list();

System.out.println("list = " + list);

in

Query query = session.createQuery("FROM Node WHERE id IN(:ids)");

query.setParameterList("ids",new Object[]{4,6,7});

List list = query.list();

System.out.println("list = " + list);

//In 的效率很低

写在配置文件里

User.hbm.xml

<hibernate-mapping>

...

<query name="getUserByAge">

    FROM Node WHERE id between ? AND ?

</query>

...

</hibernate-mapping>

代码部分

Query query = session.getNamedQuery("getUserByAge");

query.setParameter(0,6);

query.setParameter(1,8);

List list = query.list();

System.out.println("list = " + list);

完全的sql写法

仿照第一种半sql写法,格式变化就可以

1.原生sql写法

SQLQuery query = session.createSQLQuery("SELECT * FROM tree");

query.addEntity(Node.class);

List list = query.list();

System.out.println("list = " + list);

完全的面向对象写法

仿照第一种半sql写法,格式变化就可以

Criteria criteria = session.createCriteria(Node.class);

criteria.add(Restrictions.eq("id",6));

List list = criteria.list();

System.out.println("list = " + list);

相当于查出来了所有的放在criteria里面

不等于
排序
添加分页
分组聚合

不等于

Criteria criteria = session.createCriteria(Node.class);

criteria.add(Restrictions.ne("id",1));

List list = criteria.list();

System.out.println("list = " + list);

排序

Criteria criteria = session.createCriteria(Node.class);

criteria.addOrder(Order.desc("id"));

List list = criteria.list();

System.out.println("list = " + list);

添加分页

Criteria criteria = session.createCriteria(Node.class);

criteria.add(Restrictions.ne("id",1));

criteria.setFirstResult(0);

criteria.setMaxResults(2);

List list = criteria.list();

System.out.println("list = " + list);

分组聚合

Criteria criteria = session.createCriteria(Node.class);

ProjectionList projectionList = Projections.projectionList();

projectionList.add(Projections.sum("id"));

projectionList.add(Projections.groupProperty("type"));

criteria.setProjection(projectionList);

List list = criteria.list();

for (Object o : list) {

    Object[] result = (Object[]) o;

System.out.println(Arrays.toString(result));

}