Related
- cst.zju Java-OOP course week 2
- connect java code with mysql database
- Design Pattern -- Factory pattern
- Service and Dao
-
the usage of Junit,Maven
Materials
my code on github
Youtube Course on Hibernate
Overview
简单地说，hibernate 完成了一种映射操作，就是将关系型数据库中表映射成为了一个java对象,这样就为代码操作实际的数据库提供了很多方便.
hibernate是对JDBC的进一步封装，完成从对象（Object）到关系(Relation)的映射(Mapping)，也就是一个ORM框架．
copied
这里一个图很清楚表达了hibernate的组件构成．在配置文件中写的xml被Configure实例对象读取之后可以创建sessionFactory对象，用这个工厂对象可以进一步创建Session，创建连接，操作数据库．
配置文件(默认为hibernate.cfg.xml)中申明了一些必要的配置信息，如数据库的地址，端口号，数据库用户名，密码，映射类等等信息．
Code
Dao层用来操作数据库（增删改查）的基本操作，这几乎是web应用程序所默认的，使用课堂上的例子，来完成一个对user(有三个字段,自增的id,name(char(30)), 和address(char(50))表的操作．
我们建立了一个User类，这个User类的字段和user表中的字段一致，并且有getter/setter方法
package cst.zju.edu.alexsun.model;
import javax.persistence.*;
@Entity
@Table(name = "user")
public class User {
@Id
@Column(name="id")
@GeneratedValue
private int id;
@Column(name="name")
private String name;
@Column(name="address")
private String address;
public User(){
this.id = 6666;
this.name = "6666";
this.address = "6666";
}
public User(int id, String name, String address){
this.name = name;
this.id = id;
this.address = address;
}
public void setId(int id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
}
public void setAddress(String address) {
this.address = address;
}
@Id
@GeneratedValue
public int getId(){
return id;
}
public String getName(){
return this.name;
}
public String getAddress(){
return this.address;
}
@Override
public String toString() {
return "student id: " + id + " name: "+name+" address in " + address;
}
}
用注解的方法标注对应数据库表中的字段．
用UserDao设计增删改操作
package cst.zju.edu.alexsun.Dao;
import cst.zju.edu.alexsun.model.User;
import cst.zju.edu.alexsun.util.HibernateUtil;
import org.hibernate.Session;
public class UserDao implements IUserDao {
public void addUser(User user) {
Session session = null;
try {
session = HibernateUtil.openSession();
session.beginTransaction();
session.save(user);
session.getTransaction().commit();
} catch (Exception e) {
// handle the exception
throw new RuntimeException(e);
} finally {
HibernateUtil.close(session);
}
}
public User getUserByName(String userName) {
Session session = null;
User user = null;
try {
session = HibernateUtil.openSession();
user = (User) session.createQuery("from User where name = ?")
.setParameter(0, userName).uniqueResult();
} catch (Exception e) {
// handle the exception
throw new RuntimeException(e);
} finally {
HibernateUtil.close(session);
}
return user;
}
public void delete(User user) {
Session session = null;
try {
session = HibernateUtil.openSession();
session.beginTransaction();
session.delete(user);
session.getTransaction().commit();
} catch (Exception e) {
// handle the exception
throw new RuntimeException(e);
} finally {
HibernateUtil.close(session);
}
}
}
用HibernateUtil进行连接，设置配置属性．
package cst.zju.edu.alexsun.util;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
public class HibernateUtil {
private final static SessionFactory FACTORY = buildSessionFactory();
private static SessionFactory buildSessionFactory() {
Configuration cfg = new Configuration().configure();
ServiceRegistry serviceRegistry = new ServiceRegistryBuilder()
.applySettings(cfg.getProperties()).buildServiceRegistry();
SessionFactory factory = cfg.buildSessionFactory(serviceRegistry);
return factory;
}
public static SessionFactory getSessionFactory() {
return FACTORY;
}
public static Session openSession() {
return FACTORY.openSession();
}
public static void close(Session session) {
if (session != null)
session.close();
}
}
