Hibernate使用——入门

读过<<深入浅出Hibernate>> 了解到 ORM，系统设计分层思想，现在仅对Hibernate（4.1.4）这一持久层实现框架的使用作笔录以备忘之.

基本概念

1.Hibernate 是一种“对象——关系数据映射组件”，它使用映射文件将对象（Object）与关系型数据（Relational）相关联。在Hibernate中，映射文件通常以.hbm.xml作为后缀。

2.Configuration 负责管理Hibernate的DB配置信息，如url，username等，

一般Configuration configuration = new Configuration().configure();这样创建，默认下会在类路径下找hibernate.cfg.xml或者hibernate.properties配置文件读取配置信息。

若不想取用默认方式读取配置，可以这样：

File f = new File("yourpath\\yourfilename.xml");

Configuration configuration = new Configuration().configure(f);

3.获取configuration只为创建sessionFactory，从Ver.4之后这样创建:

  Configuration configuration = new Configuration().configure();

ServiceRegistry serviceRegistry = new ServiceRegistryBuilder()

.applySettings(configuration.getProperties()).buildServiceRegistry();

sessionFactory 会根据configuration当前的配置被构建，之后对configuration的任何变更将不会到已创建的sessionFactory，sessionFactory的创建代价高昂，系统设计中应充分考虑重用，sessionFactory线程安全，所以一般针对一个数据库共享一个sessionFactory。

4.Session， Hibernate完成增删改查的核心所在，session非线程安全。

Ver.4之后session创建有两种方式：

getCurrentSession()与openSession(）
* 采用getCurrentSession()创建的session会绑定到当前线程中，而采用openSession() 
创建的session则不会 
* 采用getCurrentSession()创建的session在commit或rollback时会自动关闭，而采用openSession()创建的session必须手动关闭，顾名思义，此方法必须使用于session已在早前创建的情形下，否则报错

使用getCurrentSession()需要在hibernate.cfg.xml文件中加入如下配置： 
* 如果使用的是本地事务（jdbc事务） 
<property name="hibernate.current_session_context_class">thread</property> 
* 如果使用的是全局事务（jta事务） 
<property name="hibernate.current_session_context_class">jta</property> 

此处盗用一下别人的图，联结上述：

 O/R映射——hibernate之核心所在（个人观点）。

数据类型映射：

       1）hibernate基本数据类型，仅附上一表以查阅：

    2）实体映射，本质就是实体类与数据库表之间的映射，简称类表映射，其包括以下三项：

                   a)  表名——类名映射

                   b)  主键映射

                   c)  字段映射

以下是简单的增删改查示例，DB是mysql，项目是maven构建，用了hibernate4.1.4Final版本

项目目录结构：

立刻打码如下：

1. mysql 建表sql

create table t_user (
  id int(11) not null auto_increment,
  name varchar(80) not null default '',
  primary key (id)
);

2.pom.xml(maven 项目，不知其所以者可先google一番，此处仅用作添加jar包资源)

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<groupId>learnHibernate</groupId>
	<artifactId>learnHibernate</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>learnHibernate</name>
	<url>http://maven.apache.org</url>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	</properties>

	<dependencies>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>4.8.2</version>
			<scope>test</scope>
		</dependency>

		<dependency>
			<groupId>org.hibernate</groupId>
			<artifactId>hibernate-entitymanager</artifactId>
			<version>4.1.4.Final</version>
		</dependency>

		<dependency>
			<groupId>org.hibernate</groupId>
			<artifactId>hibernate-ehcache</artifactId>
			<version>4.1.4.Final</version>
		</dependency>

		<dependency>
			<groupId>org.hibernate</groupId>
			<artifactId>hibernate-c3p0</artifactId>
			<version>4.1.4.Final</version>
		</dependency>

		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<version>5.1.15</version>
		</dependency>

                 <dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-log4j12</artifactId>
			<version>1.6.1</version>
		</dependency>
	</dependencies>
</project>

 3.hibernate.cfg.xml （各项参数需要根据阁下实际情况做相应变动）

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
          "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
          "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

	<session-factory>
		<property name="hibernate.connection.driver_class">
			com.mysql.jdbc.Driver
        </property>
		<property name="hibernate.dialect">
			org.hibernate.dialect.MySQLDialect
        </property>
		<property name="hibernate.connection.url">
			jdbc:mysql://localhost:3306/hibernate
        </property>
		<property name="hibernate.connection.username">
			root
       </property>
		<property name="hibernate.connection.password">
			root
        </property>
		<property name="hibernate.show_sql">
			true
		</property>
		<property name="hibernate.format_sql">
			true
		</property>

		<!-- 配置C3P0 -->
		<property name="hibernate.connection.provider_class">
			org.hibernate.service.jdbc.connections.internal.C3P0ConnectionProvider
        </property>
		<property name="hibernate.c3p0.max_size">10</property>
		<property name="hibernate.c3p0.min_size">1</property>
		<property name="hibernate.c3p0.max_statements">3</property>
		<property name="hibernate.c3p0.timeout">30</property>
		<property name="hibernate.c3p0.acquire_increment">1</property>
		<property name="hibernate.c3p0.idle_test_periodt">10</property>

		<!-- 配置二级缓存 -->
		<property name="hibernate.cache.use_second_level_cache">true</property>
		<property name="hibernate.cache.use_query_cache">true</property>

		<!-- Hibernate4 这里和Hibernate3不一样 要特别注意！！！-->

		<property name="hibernate.cache.region.factory_class">
			org.hibernate.cache.EhCacheRegionFactory
		</property>
		<!-- Hibernate3 -->
		<!--
			<property name="hibernate.cache.provider_class">org.hibernate.cache.EhCacheProvider</property>
		-->
		
		<!-- 实体映射文件 -->
		<mapping resource="learnHibernate/bean/TUser.hbm.xml" />

	</session-factory>

</hibernate-configuration>

 4.Tuser.java

package learnHibernate.bean;

import java.io.Serializable;

public class TUser implements Serializable{
	private static final long serialVersionUID = -2983670695642662371L;
	
	private int id;
	private String 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;
	}
}

 5. Tuser.hbm.xml

<?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="learnHibernate.bean">
	<class name="TUser" table="t_user">
		<id name="id" column="id" type="java.lang.Integer">
			<generator class="native"/>
		</id>
		
		<property name="name" column="name" type="java.lang.String"/>
	</class>
	
</hibernate-mapping>

 6. HibernateLocalUtil.java  (用于获取sessionFactory对象)

package learnHibernate.util;

import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;

public final class HibernateLocalUtil {

	private static SessionFactory sessionFactory;	
	
	private HibernateLocalUtil() {
		
	}
	
	static {
		try {
			Configuration configuration = new Configuration().configure("hibernate\\hibernate.cfg.xml");
			ServiceRegistry serviceRegistry = new ServiceRegistryBuilder()
						.applySettings(configuration.getProperties()).buildServiceRegistry();
			sessionFactory = configuration.buildSessionFactory(serviceRegistry);
			
		}catch (Throwable e) {
			throw new ExceptionInInitializerError(e);
		}
	}
	
	public static SessionFactory getSessionFactory () {
		return sessionFactory;
	}
}

 7. TestCase.java

package learnHibernate;

import java.io.Serializable;
import java.util.List;

import learnHibernate.bean.TUser;
import learnHibernate.util.HibernateLocalUtil;

import org.hibernate.Criteria;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.junit.Test;

public class TestCase {
	
	//@Test
	public void saveTUser() {
		SessionFactory sessionFactory = HibernateLocalUtil.getSessionFactory();
		Session session = sessionFactory.openSession();
		
		TUser t1 = new TUser();
		t1.setName("Cancan");
		Transaction tx = session.beginTransaction();
		Serializable id = session.save(t1);
		tx.commit();
		session.close();
		
		System.out.println("id = " + id);
	}
	
	//@Test
	public void updateTUser() {
		TUser t1 = new TUser();
		t1.setId(3);
		t1.setName("Maomao");
		
		SessionFactory sessionFactory = HibernateLocalUtil.getSessionFactory();
		Session session = sessionFactory.openSession();
		Transaction tx = session.beginTransaction();
		session.update(t1);
		tx.commit();
		session.close();
	}
	
	//@Test
	public void deleteTUser() {
		TUser t1 = new TUser();
		t1.setId(4);
		
		SessionFactory sessionFactory = HibernateLocalUtil.getSessionFactory();
		Session session = sessionFactory.openSession();
		Transaction tx = session.beginTransaction();
		session.delete(t1);
		tx.commit();
		session.close();
	}
	
	@Test
	public void selectAll() {
		SessionFactory sessionFactory = HibernateLocalUtil.getSessionFactory();
		Session session = sessionFactory.openSession();
		
		Criteria criteria = session.createCriteria(TUser.class);
		List<TUser> list = criteria.list();
		
		showList(list);
		
	}
	
	
	private void showList(List<TUser> list) {
		for(TUser t : list) {
			System.out.println(t.getId() + " -- " + t.getName());
		}
	}
}

 7.忘了一个log4j.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
    <appender name="console" class="org.apache.log4j.ConsoleAppender">
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%d [%t] %-5p %c - %m%n" />
        </layout>
    </appender>
   
  

	<logger name="com.hibernate" additivity="false">
		<level value="info" />
		 <appender-ref ref="console" />
	</logger>
	
	<logger name="com.mchange" additivity="false">
		<level value="info" />
		 <appender-ref ref="console" />
	</logger>
	
    <root>
      <level value="info" />
      <appender-ref ref="console" />
    </root>
</log4j:configuration>

 至此入门上手结束，对hibernate只得一个大体上的感受。。。

项目见附件处