Hibernate详细教程
2021-07-02 09:04
阅读：547
标签：ips except 就会 arc service update 集合属性 tran person
一、搭建Hibernate环境
1.在src目录下创建hibernate.cfg.xml配置文件
PS:文件的名字不能改！
root 1234 com.mysql.jdbc.Driver jdbc:mysql://localhost:3306/test org.hibernate.dialect.MySQL5InnoDBDialect true
update none
2. 编写实体类，以Person类为例
package test.Hibernate.model;
import java.util.HashSet;
import java.util.Set;
public class Person {
@Override
public String toString() {
return "Person [id=" + id + ", name=" + name + "]";
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Set getAddress() {
return address;
}
public void setAddress(Set address) {
this.address = address;
}
private int id;
private String name;
private Set address = new HashSet();
}
3.编写Person.hbm.xml实体类配置文件
4.在hibernate.cfg.xml中加入映射信息
5.使用MyEclipse生成SessionFactory
package test.Hibernate.SessionFactory;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
/**
* Configures and provides access to Hibernate sessions, tied to the
* current thread of execution. Follows the Thread Local Session
* pattern, see {@link http://hibernate.org/42.html }.
*/
public class SessionFactory {
/**
* Location of hibernate.cfg.xml file.
* Location should be on the classpath as Hibernate uses
* #resourceAsStream style lookup for its configuration file.
* The default classpath location of the hibernate config file is
* in the default package. Use #setConfigFile() to update
* the location of the configuration file for the current session.
*/
private static final ThreadLocal threadLocal = new ThreadLocal();
private static org.hibernate.SessionFactory sessionFactory;
private static Configuration configuration = new Configuration();
private static ServiceRegistry serviceRegistry;
static {
try {
configuration.configure();
serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()).buildServiceRegistry();
sessionFactory = configuration.buildSessionFactory(serviceRegistry);
} catch (Exception e) {
System.err.println("%%%% Error Creating SessionFactory %%%%");
e.printStackTrace();
}
}
private SessionFactory() {
}
/**
* Returns the ThreadLocal Session instance. Lazy initialize
* the SessionFactory if needed.
*
* @return Session
* @throws HibernateException
*/
public static Session getSession() throws HibernateException {
Session session = (Session) threadLocal.get();
if (session == null || !session.isOpen()) {
if (sessionFactory == null) {
rebuildSessionFactory();
}
session = (sessionFactory != null) ? sessionFactory.openSession()
: null;
threadLocal.set(session);
}
return session;
}
/**
* Rebuild hibernate session factory
*
*/
public static void rebuildSessionFactory() {
try {
configuration.configure();
serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()).buildServiceRegistry();
sessionFactory = configuration.buildSessionFactory(serviceRegistry);
} catch (Exception e) {
System.err.println("%%%% Error Creating SessionFactory %%%%");
e.printStackTrace();
}
}
/**
* Close the single hibernate session instance.
*
* @throws HibernateException
*/
public static void closeSession() throws HibernateException {
Session session = (Session) threadLocal.get();
threadLocal.set(null);
if (session != null) {
session.close();
}
}
/**
* return session factory
*
*/
public static org.hibernate.SessionFactory getSessionFactory() {
return sessionFactory;
}
/**
* return hibernate configuration
*
*/
public static Configuration getConfiguration() {
return configuration;
}
}
6.编写测试类
package test.Hibernate.dao;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.junit.Test;
import test.Hibernate.SessionFactory.SessionFactory;
import test.Hibernate.model.Person;
public class PersonDao {
@Test
public void add(){
Session session = SessionFactory.getSession();
Transaction tr = session.beginTransaction();
//----------------------------------------------
Person p = new Person();
p.setName("test");
p.getAddress().add("firstAddr");
p.getAddress().add("secondAddr");
p.getAddress().add("thirdAddr");
p.getAddress().add("fourthAddr");
session.save(p);
//----------------------------------------------
tr.commit();
SessionFactory.closeSession();
}
@Test
public void get(){
Session session = SessionFactory.getSession();
Transaction tr = session.beginTransaction();
//----------------------------------------------
Person p = (Person)session.get(Person.class, 2);
System.out.println(p);
//----------------------------------------------
tr.commit();
SessionFactory.closeSession();
}
}
二、主键生成策略
identity：使用数据库的自动增长策略，不是所有数据库都支持，比如oracle就不支持。
sequence：在 DB2，PostgreSQL，Oracle，SAP DB，McKoi 中使用序列（sequence）在使用Oracle数据库时可以使用这一个。
hilo:使用高低位算法生成主键值。只需要一张额外表，所有的数据都支持。
native:根据底层数据库的能力选择 identity、sequence 或者 hilo中的一个。
assigned：手工指定主键值。
uuid：由Hibernate自动生成UUID并指定为主键值。
三、Hibernate映射关系配置
1.一对一映射（以主键关联作为示例）User与IdCard（有外键方）的XML配置：
user
2.一对多，多对一（以Father和Children为例）
3.多对多（以Student和Teacher为例）
PS:有一方的set集合要标明inverse=true（后面会讲）
四、inverse和cascade的区别（个人总结，有不对还望指正）
1.inverse=false在一对多删除时是把孩子的外键设置为null，然后删除父亲，孩子不删除，而casecade=all在一对多删除时是把孩子的外键设置为null，然后删除父亲，然后再删除孩子
2.many to many的时候由一方维护，所以一方要设置inverse=false，但是inverse=true的另一方直接删除会出错，这个时候可以用casecade完成级联删除
3.inverse=false只用于set等集合属性，在one to one关系中可以用casecade完成级联删除
五、使用C3P0连接池
1.需要额外导入3个jar包
2.在hibernate.cfg.xml中加入C3P0配置信息
org.hibernate.connection.C3P0ConnectionProvider 5 20 120 3000
六、HQL语句
@Test
public void HQLSearch(){
Session session = SessionFactory.getSession();
Transaction tr = session.beginTransaction();
//-----------------------------------------
//common search with where
// String hql= "select e.id,e.name from User e where e.id>=5 and e.id=? and id
七、DML语句
@Test
public void DML(){
Session session = SessionFactory.getSession();
Transaction tr = session.beginTransaction();
//-----------------------------------------
User u = (User)session.get(User.class, 11);
String sql = "update User set name=? where id>?";
int result = session.createQuery(sql)
.setParameter(0, "updated")
.setParameter(1, 10)
.executeUpdate();
System.out.println("count of update:"+result);
//the object‘s status in session was not updated when the object in database have been changed,so if you want
//to get the updated object in session,you should use method "refresh".
session.refresh(u);
System.out.println(u);
//-----------------------------------------
tr.commit();
SessionFactory.closeSession();
}
八、开启二级缓存
1. 需要导入以下jar包
2.在hibernate.cfg.xml中加入以下配置
true org.hibernate.cache.ehcache.EhCacheRegionFactory true
九、Hibernate对象状态及转化
Hibernate详细教程
标签：ips except 就会 arc service update 集合属性 tran person
原文地址：http://www.cnblogs.com/zhujiabin/p/7128420.html
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