hibernate应用实例

一、在Java应用中使用Hibernate的步骤

创建Hibernate的配置文件
创建持久化类
创建对象-关系映射文件
通过Hibernate API编写访问数据库的代

二、Helloapp应用的结构



三、Hibernate的配置文件(hibernate.properties)

hibernate.dialect=org.hibernate.dialect.MySQLDialect

hibernate.connection.driver_class=com.mysql.jdbc.Driver

hibernate.connection.url=jdbc:mysql://localhost:3306/SAMPLEDB

hibernate.connection.username=root

hibernate.connection.password=1234

hibernate.show_sql=true

四、创建持久化类Customer

持久化类符合JavaBean的规范，包含一些属性，以及与之对应的getXXX()和setXXX()方法。
持久化类有一个id属性，用来惟一标识Customer类的每个对象。在面向对象术语中，这个id属性被称为对象标识符（OID，Object Identifier），通常它都用整数表示
Hibernate要求持久化类必须提供一个不带参数的默认构造方法

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package mypack;

import java.io.Serializable;

import java.sql.Date;

import java.sql.Timestamp;

public class Customer implements Serializable {

private Long id;

private String name;

private String email;

private String password;

private int phone;

private String address;

private char sex;

private boolean married;

private String description;

private byte[] image;

private Date birthday;

private Timestamp registeredTime;

public Customer(){}

public Long getId(){

return id;

}

private void setId(Long id){

this.id = id;

}

public String getName(){

return name;

}

public void setName(String name){

this.name=name;

}

public String getEmail(){

return email;

}

public void setEmail(String email){

this.email =email ;

}

public String getPassword(){

return password;

}

public void setPassword(String password){

this.password =password ;

}

public int getPhone(){

return phone;

}

public void setPhone(int phone){

this.phone =phone ;

}

public String getAddress(){

return address;

}

public void setAddress(String address){

this.address =address ;

}

public char getSex(){

return sex;

}

public void setSex(char sex){

this.sex =sex ;

}

public boolean isMarried(){

return married;

}

public void setMarried(boolean married){

this.married =married ;

}

public String getDescription(){

return description;

}

public void setDescription(String description){

this.description =description ;

}

public byte[] getImage() {

return this.image;

}

public void setImage(byte[] image) {

this.image = image;

}

public Date getBirthday() {

return this.birthday;

}

public void setBirthday(Date birthday) {

this.birthday = birthday;

}

public Timestamp getRegisteredTime() {

return this.registeredTime;

}

public void setRegisteredTime(Timestamp registeredTime) {

this.registeredTime = registeredTime;

}

}

注意：

getXXX()和setXXX()方法可以采用任意的访问级别，他的命名规则必须符合特定的命名规则，“get”和“set”后面紧跟属性的名字，并且属性名的首字母为大写，如name属性的get方法为getName()。
如果持久化类的属性为boolean类型，那么它的get方法名可以用get做前缀也可以用is做前缀。

五、创建数据库Schema

drop database if exists SAMPLEDB;

create database SAMPLEDB;

use SAMPLEDB;

create table CUSTOMERS (

ID bigint not null primary key,

NAME varchar(15) not null,

EMAIL varchar(128) not null,

PASSWORD varchar(8) not null,

PHONE int ,

ADDRESS varchar(255),

SEX char(1) ,

IS_MARRIED bit,

DESCRIPTION text,

IMAGE blob,

BIRTHDAY date,

REGISTERED_TIME timestamp

);

六、创建对象-关系映射文件Customer.hbm.xml

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC"-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

<class name="mypack.Customer" table="CUSTOMERS">

<id name="id" column="ID" type="long">

<generator class="increment"/>

</id>

<property name="name" column="NAME" type="string" not-null="true" />

<property name="email" column="EMAIL" type="string" not-null="true" />

<property name="password" column="PASSWORD" type="string" not-null="true"/>

<property name="phone" column="PHONE" type="int" />

<property name="address" column="ADDRESS" type="string" />

<property name="sex" column="SEX" type="character"/>

<property name="married" column="IS_MARRIED" type="boolean"/>

<property name="description" column="DESCRIPTION" type="text"/>

<property name="image" column="IMAGE" type="binary"/>

<property name="birthday" column="BIRTHDAY" type="date"/>

<property name="registeredTime" column="REGISTERED_TIME" type="timestamp"/>

</class>

</hibernate-mapping>

<id>元素映射OID

<generator>子元素用来设定标识符生成器。Hibernate提供了提供了多种内置的实现。



<property>元素映射值类型属性

name属性：指定持久化类的属性的名字。
column属性：指定与类的属性映射的表的字段名。
type属性：指定Hibernate映射类型。Hibernate映射类型是Java类型与SQL类型的桥梁。



采用XML文件来配置对象-关系映射的优点：

Hibernate既不会渗透到上层域模型中，也不会渗透到下层数据模型中。
软件开发人员可以独立设计域模型，不必强迫遵守任何规范。
数据库设计人员可以独立设计数据模型，不必强迫遵守任何规范。
对象-关系映射不依赖于任何程序代码，如果需要修改对象-关系映射，只需修改XML文件，不需要修改任何程序，提高了软件的灵活性，并且使维护更加方便。

七、创建BusinessService类



package mypack;

import javax.servlet.*;

import org.hibernate.*;

import org.hibernate.cfg.Configuration;

import java.io.*;

import java.sql.Date;

import java.sql.Timestamp;

import java.util.*;

public class BusinessService{

public static SessionFactory sessionFactory;

/** 初始化Hibernate，创建SessionFactory实例 */

static{

try{

// 根据默认位置的Hibernate配置文件的配置信息，创建一个Configuration实例

Configuration config = new Configuration();

//加载Customer类的对象-关系映射文件

config.addClass(Customer.class);

// 创建SessionFactory实例 */

sessionFactory = config.buildSessionFactory();

}catch(RuntimeException e){e.printStackTrace();throw e;}

}

/** 查询所有的Customer对象，然后调用printCustomer()方法打印Customer对象信息 */

public void findAllCustomers(ServletContext context,PrintWriter out) throws Exception{

Session session = sessionFactory.openSession(); //创建一个会话

Transaction tx = null;

try {

tx = session.beginTransaction(); //开始一个事务

Query query=session.createQuery("from Customer as c order by c.name asc");

List customers=query.list();

for (Iterator it = customers.iterator(); it.hasNext();) {

printCustomer(context,out,(Customer) it.next());

}

tx.commit(); //提交事务

}catch (RuntimeException e) {

if (tx != null) {

tx.rollback();

}

throw e;

} finally {

session.close();

}

}

/** 持久化一个Customer对象 */

public void saveCustomer(Customer customer){

Session session = sessionFactory.openSession();

Transaction tx = null;

try {

tx = session.beginTransaction();

session.save(customer);

tx.commit();

}catch (RuntimeException e) {

if (tx != null) {

tx.rollback();

}

throw e;

} finally {

session.close();

}

}

/** 按照OID加载一个Customer对象，然后修改它的属性 */

public void loadAndUpdateCustomer(Long customer_id,String address){

Session session = sessionFactory.openSession();

Transaction tx = null;

try {

tx = session.beginTransaction();

Customer c=(Customer)session.get(Customer.class,customer_id);

c.setAddress(address);

tx.commit();

}catch (RuntimeException e) {

if (tx != null) {

tx.rollback();

}

throw e;

} finally {

session.close();

}

}

/**删除Customer对象 */

public void deleteCustomer(Customer customer){

Session session = sessionFactory.openSession();

Transaction tx = null;

try {

tx = session.beginTransaction();

session.delete(customer);

tx.commit();

}catch (RuntimeException e) {

if (tx != null) {

tx.rollback();

}

throw e;

} finally {

session.close();

}

}

/** 选择向控制台还是Web网页输出Customer对象的信息 */

private void printCustomer(ServletContext context,PrintWriter out,Customer customer)throws Exception{

if(context!=null)

printCustomerInWeb(context,out,customer);

else

printCustomer( out,customer);

}

/** 把Customer对象的信息输出到控制台，如DOS 控制台*/

private void printCustomer(PrintWriter out,Customer customer)throws Exception{

byte[] buffer=customer.getImage();

FileOutputStream fout=new FileOutputStream("photo_copy.gif");

fout.write(buffer);

fout.close();

out.println("------以下是"+customer.getName()+"的个人信息------");

out.println("ID: "+customer.getId());

out.println("口令: "+customer.getPassword());

out.println("E-Mail: "+customer.getEmail());

out.println("电话: "+customer.getPhone());

out.println("地址: "+customer.getAddress());

String sex=customer.getSex()=='M'? "男":"女";

out.println("性别: "+sex);

String marriedStatus=customer.isMarried()? "已婚":"未婚";

out.println("婚姻状况: "+marriedStatus);

out.println("生日: "+customer.getBirthday());

out.println("注册时间: "+customer.getRegisteredTime());

out.println("自我介绍: "+customer.getDescription());

}

/** 把Customer对象的信息输出到动态网页 */

private void printCustomerInWeb(ServletContext context,PrintWriter out,Customer customer)throws Exception{

//保存照片

byte[] buffer=customer.getImage();

String path=context.getRealPath("/");

FileOutputStream fout=new FileOutputStream(path+"photo_copy.gif");

fout.write(buffer);

fout.close();

out.println("------以下是"+customer.getName()+"的个人信息------"+"<br>");

out.println("ID: "+customer.getId()+"<br>");

out.println("口令: "+customer.getPassword()+"<br>");

out.println("E-Mail: "+customer.getEmail()+"<br>");

out.println("电话: "+customer.getPhone()+"<br>");

out.println("地址: "+customer.getAddress()+"<br>");

String sex=customer.getSex()=='M'? "男":"女";

out.println("性别: "+sex+"<br>");

String marriedStatus=customer.isMarried()? "已婚":"未婚";

out.println("婚姻状况: "+marriedStatus+"<br>");

out.println("生日: "+customer.getBirthday()+"<br>");

out.println("注册时间: "+customer.getRegisteredTime()+"<br>");

out.println("自我介绍: "+customer.getDescription()+"<br>");

out.println("<img src='photo_copy.gif' border=0><p>");

}

public void test(ServletContext context,PrintWriter out) throws Exception{

Customer customer=new Customer();

customer.setName("Tom");

customer.setEmail("tom@yahoo.com");

customer.setPassword("1234");

customer.setPhone(55556666);

customer.setAddress("Shanghai");

customer.setSex('M');

customer.setDescription("I am very honest.");

//设置Customer对象的image属性，它是字节数组，存放photo.gif文件中的二进制数据

//photo.gif文件和BusinessService.class文件位于同一个目录下

InputStream in=this.getClass().getResourceAsStream("photo.gif");

byte[] buffer = new byte[in.available()];

in.read(buffer);

customer.setImage(buffer);

//设置Customer对象的birthday属性，它是java.sql.Date类型

customer.setBirthday(Date.valueOf("1980-05-06"));

saveCustomer(customer);

findAllCustomers(context,out);

loadAndUpdateCustomer(customer.getId(),"Beijing");

findAllCustomers(context,out);

deleteCustomer(customer);

}

public static void main(String args[]) throws Exception {

new BusinessService().test(null,new PrintWriter(System.out,true));

sessionFactory.close();

}

}







saveCustomer()方法

该方法调用Session的save()方法，把Customer对象持久化到数据库中。

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tx = session.beginTransaction();

session.save(customer);

tx.commit();

Java代码


tx = session.beginTransaction();

session.save(customer);

tx.commit();

当运行session.save()方法时，Hibernate执行以下SQL语句：

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insert into CUSTOMERS (ID, NAME, EMAIL, PASSWORD, PHONE, ADDRESS, SEX,

IS_MARRIED,DESCRIPTION, IMAGE, BIRTHDAY, REGISTERED_TIME)

values(1,'Tom','tom@yahoo.com','1234',55556666,'Shanghai','M',0,'I am very honest.', ☺,'1980-05-06',null)

Sql代码


insert into CUSTOMERS (ID, NAME, EMAIL, PASSWORD, PHONE, ADDRESS, SEX,

IS_MARRIED,DESCRIPTION, IMAGE, BIRTHDAY, REGISTERED_TIME)

values(1,'Tom','tom@yahoo.com','1234',55556666,'Shanghai','M',0,'I am very honest.', ☺,'1980-05-06',null)

在test()方法中并没有设置Customer对象的id属性，Hibernate会根据映射文件的配置，采用increment标识符生成器自动以递增的方式为OID赋值。在Customer.hbm.xml文件中相关的映射代码如下：

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<id name="id" column="ID" type="long">

<generator class="increment"/>

</id>

Html代码


<id name="id" column="ID" type="long">

<generator class="increment"/>

</id>

findAllCustomers()方法

该方法通过Query接口查询所有的Customer对象。

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tx = session.beginTransaction(); //开始一个事务

Query query=session.createQuery("from Customer as c order by c.name asc");

List customers=query.list();

for (Iterator it = customers.iterator(); it.hasNext();) {

printCustomer(context,out,(Customer) it.next());

}

tx.commit(); //提交事务

Java代码


tx = session.beginTransaction(); //开始一个事务

Query query=session.createQuery("from Customer as c order by c.name asc");

List customers=query.list();

for (Iterator it = customers.iterator(); it.hasNext();) {

printCustomer(context,out,(Customer) it.next());

}

tx.commit(); //提交事务

Session的createQuery()方法的参数“from Customer as c order by c.name asc”使用的是Hibernate查询语言。运行Query.list()方法时， Hibernate执行以下SQL语句：

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select * from CUSTOMERS order by NAME asc;

Sql代码


select * from CUSTOMERS order by NAME asc;

loadAndUpdateCustomer ()方法

该方法调用Session的get()方法，加载Customer对象，然后再修改Customer对象的属性。

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tx = session.beginTransaction();

Customer c=(Customer)session.get(Customer.class,customer_id);

c.setAddress(address); //修改内存中Customer对象的address属性

tx.commit();

Java代码


tx = session.beginTransaction();

Customer c=(Customer)session.get(Customer.class,customer_id);

c.setAddress(address); //修改内存中Customer对象的address属性

tx.commit();

以上代码先调用Session的get()方法，它按照参数指定的OID从数据库中检索出匹配的Customer对象，Hibernate会执行以下SQL语句：

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select * from CUSTOMERS where ID=1;

Sql代码


select * from CUSTOMERS where ID=1;

loadAndUpdateCustomer()方法接着修改Customer对象的address属性。那么，Hibernate会不会同步更新数据库中相应的CUSTOMERS表的记录呢？答案是肯定的。Hibernate采用脏检查机制，按照内存中的Customer对象的状态的变化，来同步更新数据库中相关的数据，Hibernate会执行以下SQL语句：

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update CUSTOMERS set NAME="Tom",EMAIL="Tom@yahoo.com"…ADDRESS="Beijing"…

where ID=1;

Sql代码


update CUSTOMERS set NAME="Tom",EMAIL="Tom@yahoo.com"…ADDRESS="Beijing"…

where ID=1;

尽管只有Customer对象的address属性发生了变化，但是Hibernate执行的update语句中会包含所有的字段。

deleteCustomer()方法

该方法调用Session的delete()方法，删除特定的Customer对象：

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tx = session.beginTransaction();

session.delete(customer);

tx.commit();

Java代码


tx = session.beginTransaction();

session.delete(customer);

tx.commit();

运行session.delete()方法时，Hibernate根据Customer对象的OID，执行以下SQL delete语句：

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delete from CUSTOMERS where ID=1;

Sql代码


delete from CUSTOMERS where ID=1;

八、效果图