Hibernate入门教程

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Hibernate入门教程

seltonzyf 2018-06-14 10:56:00 浏览1123
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Hibernate

随心所欲的使用面向对象思想操纵数据库.


Table of contents

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

  1. jar下载
  2. 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

半sql半面向对象写法

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

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

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));
}

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