1 数据源：能够简单理解为数据的来源。

2 连接池：是缓存一定数量的数据库连接，当程序须要数据库连接的时候，直接在连接池中获取空暇的连接，使用完再放回连接池中，此连接又变成空暇状态，等待下一次连接。

有于开启连接和关闭连接比較耗费系统资源，有类连接池的管理能够降低这方面的开支。

3 常见连接池：c3p0,dbcp,proxool是常见开源的三种连接池。

Spring提供的DriverManagerDataSource总是新建一个连接，根本没有起到连接池的作用。

4 连接池获取连接的方法： Connection conn=dataSource.getConnection();

5 例如以下是数据源的使用： 

  c3p0：

UserDao:

package com.dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

import javax.sql.DataSource;

public class UserDao {
	private DataSource dataSource;
	
	public DataSource getDataSource() {
		return dataSource;
	}

	public void setDataSource(DataSource dataSource) {
		this.dataSource = dataSource;
	}

	public void save(){
		try {
			Connection conn=dataSource.getConnection();
			String sql="insert into t_student values(?,?)";
			PreparedStatement ps=conn.prepareStatement(sql);
			ps.setInt(1, 1);
			ps.setString(2, "zhang");
			ps.executeUpdate();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
}

UserService:

package com.service;

import com.dao.UserDao;

public class UserService {
	private UserDao userDao;

	public UserDao getUserDao() {
		return userDao;
	}

	public void setUserDao(UserDao userDao) {
		this.userDao = userDao;
	}
	public void save(){
		userDao.save();
	}
}

applicationContext.xml:

<?xml version="1.0" encoding="UTF-8"?
>
<beans xmlns="http://www.springframework.org/schema/beans"
		xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
		xmlns:context="http://www.springframework.org/schema/context"
		xmlns:tx="http://www.springframework.org/schema/tx"
		xmlns:aop="http://www.springframework.org/schema/aop"
		xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
		http://www.springframework.org/schema/aop 
		http://www.springframework.org/schema/aop/spring-aop-2.5.xsd">
		<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
			<property name="driverClass" value=http://www.mamicode.com/"oracle.jdbc.driver.OracleDriver">>
測试类：
package com.aop;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.service.UserService;

public class Test {

	public static void main(String[] args) {
		ApplicationContext ac=new ClassPathXmlApplicationContext("applicationContext.xml");
		UserService uc=(UserService) ac.getBean("userService");
		uc.save();
	}

}


6       为了方便维护，改动数据源，能够把数据源的值写在配置中，这样的方式是通过设置站位符实现的。使用Spring的 PropertyPlaceholderConfigurer。
    须要在spring配置中添加一个管理配置的bean，用来管理数据源取值的配置。
	<bean
		class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
		<property name="locations">
			<value>classpath:c3p0.properties</value>
		</property>
	</bean>

       classpath:配置的路径。从src文件夹開始。 

applicationContext.xml
<?xml version="1.0" encoding="UTF-8"?
>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
	xmlns:tx="http://www.springframework.org/schema/tx" xmlns:aop="http://www.springframework.org/schema/aop"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
		 http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
		http://www.springframework.org/schema/aop 
		http://www.springframework.org/schema/aop/spring-aop-2.5.xsd
		http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-2.5.xsd">
	<context:component-scan base-package="com.*" />
	<context:annotation-config />

	<bean
		class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
		<property name="locations">
			<value>classpath:c3p0.properties</value>
		</property>
	</bean>

	<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
		<property name="driverClass" value=http://www.mamicode.com/"${driverClass}">>

c3p0.properties
driverClass=oracle.jdbc.driver.OracleDriver
jdbcUrl=jdbc:oracle:thin:@localhost:1521:XE
user=orcl
password=newsnews

=前面的值要和${}里面的值相应。