1：第一种方式非常简单

c3p0.driverClass=com.mysql.jdbc.Driver
c3p0.jdbcUrl=jdbc:mysql://localhost:3308/database
c3p0.user=root
c3p0.password=root

package jdbc.mysql;

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


import com.mchange.v2.c3p0.ComboPooledDataSource;

public class C3P0 {
	public static void main(String[] args) throws SQLException {
	//数据库连接池默认会到classpath下去找数据库的配置。
		ComboPooledDataSource data = http://www.mamicode.com/new ComboPooledDataSource();>
2：第二种方式非常灵活好用，也非常接近于我们平时的hibernate和struts的配置文件方式
   而且可以为多个数据源提供服务，提供default-config和named-config两种配置方式 。
   其中里面的具体参数可参照c3p0文档(http://www.mchange.com/projects/c3p0/) 比较简单。根据属性名字几乎可以看出意思。
<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
  <default-config>
    <property name="user">root</property>
    <property name="password">1234</property>
    <property name="driverClass">com.mysql.jdbc.Driver</property>
    <property name="jdbcUrl">jdbc:mysql://localhost:3306/database?characterEncoding=UTF-8&useOldAliasMetadataBehavior=true</property> 
    <property name="initialPoolSize">2</property>
    <property name="maxIdleTime">30</property>
    <property name="maxPoolSize">100</property>
    <property name="minPoolSize">2</property>
  </default-config>
  
  <named-config name="database">
    <property name="user">root</property>
    <property name="password">root</property>
    <property name="driverClass">com.mysql.jdbc.Driver</property>
    <property name="jdbcUrl">jdbc:mysql://localhost:3308/database?characterEncoding=UTF-8&useOldAliasMetadataBehavior=true</property> 
    <property name="initialPoolSize">2</property>
    <property name="maxIdleTime">30</property>
    <property name="maxPoolSize">100</property>
    <property name="minPoolSize">2</property>
  </named-config>

</c3p0-config>

package jdbc.mysql;

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

import javax.sql.DataSource;

import com.mchange.v2.c3p0.ComboPooledDataSource;


public class C3p0JDBC {
	public static void main(String[] args) throws SQLException {
		System.setProperty("com.mchange.v2.c3p0.cfg.xml",System.getProperty("user.dir")+"/config/c3p0-config.xml");
		//上面的配置文件  <default-config> 
		//默认情况下 构造函数传空值。会去找默认配置
		DataSource data = http://www.mamicode.com/new ComboPooledDataSource();>
3：这种配置是最不常用的，比较繁琐，就是把所有配置都写到程序里面来。
可选择性使用
import com.mchange.v2.c3p0.*;
........	
ComboPooledDataSource cpds = new ComboPooledDataSource();
cpds.setDriverClass( "org.postgresql.Driver" ); //loads the jdbc driver            
cpds.setJdbcUrl( "jdbc:postgresql://localhost/testdb" );
cpds.setUser("dbuser");                                  
cpds.setPassword("dbpassword");                                  

cpds.setMaxStatements( 180 ); 
cpds.close();