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
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
- 单个数据(对象)存储到数据库
- 查询单个对象
- 更新单个对象
- 删除对象
- 查询整个表
- 查询某个对象的某个属性
- 查询指定行数据
- 查询指定数据传回一个实体
- 分组聚合
- 排序
- limit
- 使用参数
- in
- 写在配置文件里
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
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));
}