create table account(
		   id int primary key auto_increment,
		   name varchar(20),
		   money double
		);

		insert into account values(null,‘aaa‘,1000);
		insert into account values(null,‘bbb‘,1000);
		insert into account values(null,‘ccc‘,1000);

driverClass=com.mysql.jdbc.Driver
url=jdbc:mysql:///mydb1
username=root
password=root

#driverClass=oracle.jdbc.driver.OracleDriver
#url=jdbc:oracle:thin:@localhost:1521:XE
#username=system
#password=system

package cn.itcast.utils;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ResourceBundle;

//使用配置文件

public class JdbcUtils {

	private static final String DRIVERCLASS;
	private static final String URL;
	private static final String USERNAME;
	private static final String PASSWORD;

	static {
		DRIVERCLASS = ResourceBundle.getBundle("jdbc").getString("driverClass");
		URL = ResourceBundle.getBundle("jdbc").getString("url");
		USERNAME = ResourceBundle.getBundle("jdbc").getString("username");
		PASSWORD = ResourceBundle.getBundle("jdbc").getString("password");
	}

	static {
		try {
			// 将加载驱动操作，放置在静态代码块中.这样就保证了只加载一次.
			Class.forName(DRIVERCLASS);
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
	}

	public static Connection getConnection() throws SQLException {

		// 2.获取连接
		Connection con = DriverManager.getConnection(URL, USERNAME, PASSWORD);

		return con;
	}
	
	//关闭操作
	public static void closeConnection(Connection con) throws SQLException{
		if(con!=null){
			con.close();
		}
	}
	public static void closeStatement(Statement st) throws SQLException{
		if(st!=null){
			st.close();
		}
	}
	public static void closeResultSet(ResultSet rs) throws SQLException{
		if(rs!=null){
			rs.close();
		}
	}
}

package cn.itcast.transaction;

import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;

import cn.itcast.utils.JdbcUtils;

//jdbc中事务操作
public class TransactionTest1 {

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

		// 修改id=2这个人的money=500;

		String sql = "update account set money=500 where id=2";

		Connection con = JdbcUtils.getConnection();
		con.setAutoCommit(false); //开启事务，相当于  start transaction;

		Statement st = con.createStatement();
		st.executeUpdate(sql);
		
		//事务回滚
		//con.rollback();

		con.commit(); //事务提交
		st.close();
		con.close();
		
	}
}

package cn.itcast.transaction;

import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;

import cn.itcast.utils.JdbcUtils;

//jdbc中事务操作
public class TransactionTest2 {

	public static void main(String[] args) {

		// 修改id=2这个人的money=500;

		String sql = "update account set money=500 where id=1";

		Connection con = null;
		Statement st = null;

		try {
			con = JdbcUtils.getConnection();
			con.setAutoCommit(false); // 开启事务，相当于 start transaction;

			st = con.createStatement();
			st.executeUpdate(sql);
		} catch (SQLException e) {
			e.printStackTrace();
			// 事务回滚
			 try {
				con.rollback();
			} catch (SQLException e1) {
				e1.printStackTrace();
			}
		} finally {

			try {
				con.commit(); // 事务提交
				st.close();
				con.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}
}

• 原子性(Atomicity)：原子性是指事务是一个不可分割的单位，事务中的操作要么都发生，要么都不发生。
• 一致性(Consistency)：事务前后数据的完整性必须保持一致。
• 隔离性(Isolation)：事务的隔离性是指多个用户并发访问数据库时，一个用户的事务不能被其它用户的事务所干扰，多个并发事务之间数据要相互隔离。
• 持久性(Durablity)：持久性是指一个事务一旦被提交，它对数据库中的数据的改变就是永久性的，接下来即使数据库发生故障也不应该对其有任何影响。

package cn.itcast.dao;

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

import cn.itcast.exception.AccountException;
//没有使用ThreadLocal来获取Connection。
public class _AccountDaoImpl {

	// 从accountOut账户转出money
	public void accountOut(Connection con, String accountOut, double money)
			throws SQLException, AccountException {
		String sql = "update account set money=money-? where name=?";

		PreparedStatement pst = con.prepareStatement(sql);
		pst.setDouble(1, money);
		pst.setString(2, accountOut);
		int row = pst.executeUpdate();
		if (row == 0) {
			throw new AccountException("转出失败");
		}
		pst.close();
	}

	// 向accountIn账户转入money
	public void accountIn(Connection con, String accountIn, double money)
			throws SQLException, AccountException {
		String sql = "update account set money=money+? where name=?";

		PreparedStatement pst = con.prepareStatement(sql);
		pst.setDouble(1, money);
		pst.setString(2, accountIn);
		int row = pst.executeUpdate();
		if (row == 0) {
			throw new AccountException("转入失败");
		}
		pst.close();
	}

}

package cn.itcast.dao;

import java.sql.Connection;

public interface AccountDao {
	public void accountOut(String accountOut, double money) throws Exception;

	public void accountIn(String accountIn, double money) throws Exception;

}

package cn.itcast.dao;

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

import cn.itcast.exception.AccountException;
import cn.itcast.utils.JdbcUtils;

public class AccountDaoImpl implements AccountDao {

	// 从accountOut账户转出money
	public void accountOut(String accountOut, double money)
			throws SQLException, AccountException {
		String sql = "update account set money=money-? where name=?";
		Connection con=JdbcUtils.getConnection();
		PreparedStatement pst = con.prepareStatement(sql);
		pst.setDouble(1, money);
		pst.setString(2, accountOut);
		int row = pst.executeUpdate();
		if (row == 0) {
			throw new AccountException("转出失败");
		}
		pst.close();
	}

	// 向accountIn账户转入money
	public void accountIn( String accountIn, double money)
			throws SQLException, AccountException {
		String sql = "update account set money=money+? where name=?";
		Connection con=JdbcUtils.getConnection();
		PreparedStatement pst = con.prepareStatement(sql);
		pst.setDouble(1, money);
		pst.setString(2, accountIn);
		int row = pst.executeUpdate();
		if (row == 0) {
			throw new AccountException("转入失败");
		}
		pst.close();
	}

}

package cn.itcast.exception;

public class AccountException extends Exception {

	public AccountException() {
		super();
		// TODO Auto-generated constructor stub
	}

	public AccountException(String message, Throwable cause) {
		super(message, cause);
		// TODO Auto-generated constructor stub
	}

	public AccountException(String message) {
		super(message);
		// TODO Auto-generated constructor stub
	}

	public AccountException(Throwable cause) {
		super(cause);
		// TODO Auto-generated constructor stub
	}

}

package cn.itcast.utils;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ResourceBundle;

public class JdbcUtils {

	private static final String DRIVERCLASS;
	private static final String URL;
	private static final String USERNAME;
	private static final String PASSWORD;

	private static final ThreadLocal<Connection> tl = new ThreadLocal<Connection>();
	static {
		DRIVERCLASS = ResourceBundle.getBundle("jdbc").getString("driverClass");
		URL = ResourceBundle.getBundle("jdbc").getString("url");
		USERNAME = ResourceBundle.getBundle("jdbc").getString("username");
		PASSWORD = ResourceBundle.getBundle("jdbc").getString("password");
	}

	static {
		try {
			// 将加载驱动操作，放置在静态代码块中.这样就保证了只加载一次.
			Class.forName(DRIVERCLASS);
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
	}

	public static Connection getConnection() throws SQLException {
		Connection con = tl.get();// 从ThreadLocal中获取Connection。第一次获取得到的是null.

		if (con == null) {
			// 2.获取连接
			con = DriverManager.getConnection(URL, USERNAME, PASSWORD);
			tl.set(con); // 将con装入到ThreadLocal中。
		}

		// tl.remove(); //解除
		return con;
	}

	// 关闭操作
	public static void closeConnection(Connection con) throws SQLException {
		if (con != null) {
			con.close();
		}
	}

	public static void closeStatement(Statement st) throws SQLException {
		if (st != null) {
			st.close();
		}
	}

	public static void closeResultSet(ResultSet rs) throws SQLException {
		if (rs != null) {
			rs.close();
		}
	}
}

package cn.itcast.web.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import cn.itcast.exception.AccountException;
import cn.itcast.service.AccountService;

public class AccountServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html;charset=utf-8");

		// 1.得到请求参数
		String accountIn = request.getParameter("accountin");
		String accountOut = request.getParameter("accountout");

		double money = Double.parseDouble(request.getParameter("money"));

		// 2.调用service,完成汇款操作
		AccountService service = new AccountService();

		try {
			service.account(accountIn, accountOut, money);
			response.getWriter().write("转账成功");
			return;
		} catch (AccountException e) {
			e.printStackTrace();
			response.getWriter().write(e.getMessage());
			return;
		}
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

}

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    
    <title>My JSP ‘index.jsp‘ starting page</title>
  </head>
  
  <body>
	
	<form action="${pageContext.request.contextPath}/account" method="post">
		转入账户:<input type="text" name="accountin"><br>
		转出账户:<input type="text" name="accountout"><br>
		金额:<input type="text" name="money"><br>
		<input type="submit" value=http://www.mamicode.com/"提交">>看运行结果：

package cn.itcast.zq;

//使用继承增强
public class Demo1 {

	public static void main(String[] args) {
		Person1 p=new Student1();
		
		p.eat();
	}
	
}

class Person1{
	
	public void eat(){
		System.out.println("吃两个馒头");
	}
}

class Student1 extends Person1{
	
	@Override
	public void eat(){
		super.eat();
		System.out.println("加两个鸡腿");
	}
}

package cn.itcast.zq;

//使用装饰进行增强
public class Demo2 {
	public static void main(String[] args) {

		Car car=new Bmw();
		
		//给车增强
		CarDerector cd=new CarDerector(car);
		
		cd.run();
		
	}
}

interface Car {
	void run();
}

class Bmw implements Car {
	public void run() {
		System.out.println("bmw run....");
	}
}

class Benz implements Car {
	public void run() {
		System.out.println("benz run....");
	}
}

// 使用装饰来完成
class CarDerector implements Car {

	private Car car;

	public CarDerector(Car car) {
		this.car = car;
	}

	public void run() {
		System.out.println("添加导航");
		car.run();
		
	}
}

package cn.itcast.zq;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

import cn.itcast.utils.JdbcUtils;

public class Demo3 {

	public static void main(String[] args) throws SQLException, ClassNotFoundException {
		
		Class.forName("com.mysql.jdbc.Driver"); //注册驱动
				
		final Connection con = DriverManager.getConnection("jdbc:mysql:///mydb1","root","root");
		
		Connection proxy = (Connection) Proxy.newProxyInstance(con.getClass()
				.getClassLoader(), con.getClass().getInterfaces(),
				new InvocationHandler() {

					public Object invoke(Object proxy, Method method,
							Object[] args) throws Throwable {

						return method.invoke(con, args);
					}
				});

		System.out.println(proxy);

	}
}

package cn.itcast.zq;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

import cn.itcast.utils.JdbcUtils;

public class Demo3 {

	public static void main(String[] args) throws SQLException, ClassNotFoundException {
		
		Class.forName("com.mysql.jdbc.Driver"); //注册驱动
				
		final Connection con = DriverManager.getConnection("jdbc:mysql:///mydb1","root","root");
		
		Connection proxy = (Connection) Proxy.newProxyInstance(con.getClass()
				.getClassLoader(), new Class[]{Connection.class},
				new InvocationHandler() {

					public Object invoke(Object proxy, Method method,
							Object[] args) throws Throwable {

						return method.invoke(con, args);
					}
				});

		System.out.println(proxy);

	}
}

package cn.itcast.datasource;

import java.io.PrintWriter;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.util.LinkedList;
import java.util.logging.Logger;

import javax.sql.DataSource;

import cn.itcast.utils.JdbcUtils;

public class MyDataSource implements DataSource {

	private LinkedList<Connection> ll; // 用于装Connection对象的容器。

	public MyDataSource() throws SQLException {

		ll = new LinkedList<Connection>();
		// 当创建MyDateSource对象时，会向ll中装入5个Connection对象。

		for (int i = 0; i < 5; i++) {

			Connection con = JdbcUtils.getConnection();

			ll.add(con);

		}

	}

	// 获取连接方法
	public Connection getConnection() throws SQLException {

		if (ll.isEmpty()) {
			for (int i = 0; i < 3; i++) {

				Connection con = JdbcUtils.getConnection();

				ll.add(con);

			}
		}

		final Connection con = ll.removeFirst();

		Connection proxyCon = (Connection) Proxy.newProxyInstance(con
				.getClass().getClassLoader(), new Class[]{ Connection.class},
				new InvocationHandler() {

					public Object invoke(Object proxy, Method method,
							Object[] args) throws Throwable {
						if ("close".equals(method.getName())) {

							// 这代表是close方法，它要做的事情是将con对象重新装入到集合中.

							ll.add(con);
							System.out.println("重新将连接对象装入到集合中");

							return null;

						} else {
							return method.invoke(con, args);// 其它方法执行原来操作
						}
					}
				});

		return proxyCon;
	}

	// 将Connection对象重新装入.
	// public void readd(Connection con) {
	//
	// ll.addLast(con);
	//
	// }

	// public int getSize() {
	// return ll.size();
	// }

	public Connection getConnection(String username, String password)
			throws SQLException {
		return null;
	}

	public PrintWriter getLogWriter() throws SQLException {
		return null;
	}

	public void setLogWriter(PrintWriter out) throws SQLException {

	}

	public void setLoginTimeout(int seconds) throws SQLException {

	}

	public int getLoginTimeout() throws SQLException {
		return 0;
	}

	public <T> T unwrap(Class<T> iface) throws SQLException {
		return null;
	}

	public boolean isWrapperFor(Class<?> iface) throws SQLException {
		return false;
	}

	public Logger getParentLogger() throws SQLFeatureNotSupportedException {
		// TODO Auto-generated method stub
		return null;
	}

}

package cn.itcast.datasource;

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

import javax.sql.DataSource;

//测试自己定义的连接池
public class MyDataSourceTest {

	public static void main(String[] args) throws SQLException {
		DataSource mds = new MyDataSource(); // 创建一个连接池

		// 获取一个连接对象
		Connection con = mds.getConnection();

		// 操作
		ResultSet rs = con.createStatement().executeQuery(
				"select * from account");

		while (rs.next()) {

			System.out.println(rs.getInt("id") + "  " + rs.getString("name"));
		}

		rs.close();

		// 将连接对象重新装入到连接池
		// mds.readd(con);

		con.close(); // 原来作用是将Connection对象销毁，我们在使用连接池，获取Connection对象后，在调用close方法，就不在是销毁，而是将其重新放回到连接池。
		// System.out.println(mds.getSize());
	}
}

DBCP连接池

package cn.itcast.datasource;

import java.io.FileInputStream;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;

import javax.sql.DataSource;

import org.apache.commons.dbcp.BasicDataSource;
import org.apache.commons.dbcp.BasicDataSourceFactory;
import org.junit.Test;

public class DbcpTest {

	// 1.手动配置
	@Test
	public void test1() throws SQLException {

		BasicDataSource bds = new BasicDataSource();

		// 需要设置连接数据库最基本四个条件
		bds.setDriverClassName("com.mysql.jdbc.Driver");
		bds.setUrl("jdbc:mysql:///mydb1");
		bds.setUsername("root");
		bds.setPassword("root");

		// 得到一个Connection
		Connection con = bds.getConnection();

		ResultSet rs = con.createStatement().executeQuery(
				"select * from account");

		while (rs.next()) {

			System.out.println(rs.getInt("id") + "  " + rs.getString("name"));
		}

		rs.close();
		con.close(); // 将Connection对象重新装入到连接池.

	}

	// 2.自动配置
	@Test
	public void test2() throws Exception {

		Properties props = new Properties();

		// props.setProperty("driverClassName", "com.mysql.jdbc.Driver");
		// props.setProperty("url", "jdbc:mysql:///day18");
		// props.setProperty("username", "root");
		// props.setProperty("password", "abc");
		
		InputStream fis = this.getClass().getResourceAsStream("/dbcp.properties");
		props.load(fis);

		DataSource ds = BasicDataSourceFactory.createDataSource(props);

		// 得到一个Connection
		Connection con = ds.getConnection();

		ResultSet rs = con.createStatement().executeQuery(
				"select * from account");

		while (rs.next()) {

			System.out.println(rs.getInt("id") + "  " + rs.getString("name"));
		}

		rs.close();
		con.close(); // 将Connection对象重新装入到连接池.
	}
}

C3P0连接池（必会，非常重要）

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
	<default-config>
		<property name="driverClass">com.mysql.jdbc.Driver</property>
		<property name="jdbcUrl">jdbc:mysql:///mydb1</property>
		<property name="user">root</property>
		<property name="password">root</property>
	</default-config>

</c3p0-config>
	

package cn.itcast.datasource;

import java.beans.PropertyVetoException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;

import javax.sql.DataSource;

import org.apache.commons.dbcp.BasicDataSourceFactory;
import org.junit.Test;

import com.mchange.v2.c3p0.ComboPooledDataSource;

//c3p0连接池
public class C3p0Test {

	//
	@Test
	public void test1() throws PropertyVetoException, SQLException {
		ComboPooledDataSource cpds = new ComboPooledDataSource();

		cpds.setDriverClass("com.mysql.jdbc.Driver");
		cpds.setJdbcUrl("jdbc:mysql:///mydb1");
		cpds.setUser("root");
		cpds.setPassword("root");

		// 得到一个Connection
		Connection con = cpds.getConnection();

		ResultSet rs = con.createStatement().executeQuery(
				"select * from account");

		while (rs.next()) {

			System.out.println(rs.getInt("id") + "  " + rs.getString("name"));
		}

		rs.close();
		con.close(); // 将Connection对象重新装入到连接池.

	}

	@Test
	public void test2() throws PropertyVetoException, SQLException {
		ComboPooledDataSource cpds = new ComboPooledDataSource();

		// 得到一个Connection
		Connection con = cpds.getConnection();

		ResultSet rs = con.createStatement().executeQuery(
				"select * from account");

		while (rs.next()) {

			System.out.println(rs.getInt("id") + "  " + rs.getString("name"));
		}

		rs.close();
		con.close(); // 将Connection对象重新装入到连接池.

		// String path = this.getClass().getResource("/").getPath();
		// System.out.println(path);
	}
}

<c3p0-config>
 <default-config>
<!--当连接池中的连接耗尽的时候c3p0一次同时获取的连接数。Default: 3 -->
<property name="acquireIncrement">3</property>

<!--定义在从数据库获取新连接失败后重复尝试的次数。Default: 30 -->
 <property name="acquireRetryAttempts">30</property>

<!--两次连接中间隔时间，单位毫秒。Default: 1000 -->
 <property name="acquireRetryDelay">1000</property>

<!--连接关闭时默认将所有未提交的操作回滚。Default: false -->
 <property name="autoCommitOnClose">false</property>

<!--c3p0将建一张名为Test的空表，并使用其自带的查询语句进行测试。如果定义了这个参数那么
 属性preferredTestQuery将被忽略。你不能在这张Test表上进行任何操作，它将只供c3p0测试
 使用。Default: null-->
<property name="automaticTestTable">Test</property>

<!--获取连接失败将会引起所有等待连接池来获取连接的线程抛出异常。但是数据源仍有效
 保留，并在下次调用getConnection()的时候继续尝试获取连接。如果设为true，那么在尝试
 获取连接失败后该数据源将申明已断开并永久关闭。Default: false-->
<property name="breakAfterAcquireFailure">false</property>

<!--当连接池用完时客户端调用getConnection()后等待获取新连接的时间，超时后将抛出
SQLException,如设为0则无限期等待。单位毫秒。Default: 0 -->
<property name="checkoutTimeout">100</property>

<!--通过实现ConnectionTester或QueryConnectionTester的类来测试连接。类名需制定全路径。
Default: com.mchange.v2.c3p0.impl.DefaultConnectionTester-->
<property name="connectionTesterClassName"></property>

<!--指定c3p0 libraries的路径，如果（通常都是这样）在本地即可获得那么无需设置，默认null即可
Default: null-->
<property name="factoryClassLocation">null</property>

<!--Strongly disrecommended. Setting this to true may lead to subtle and bizarre bugs.
（文档原文）作者强烈建议不使用的一个属性-->
<property name="forceIgnoreUnresolvedTransactions">false</property>

<!--每60秒检查所有连接池中的空闲连接。Default: 0 -->
<property name="idleConnectionTestPeriod">60</property>

<!--初始化时获取三个连接，取值应在minPoolSize与maxPoolSize之间。Default: 3 -->
<property name="initialPoolSize">3</property>

<!--最大空闲时间,60秒内未使用则连接被丢弃。若为0则永不丢弃。Default: 0 -->
<property name="maxIdleTime">60</property>

<!--连接池中保留的最大连接数。Default: 15 -->
<property name="maxPoolSize">15</property>

<!--JDBC的标准参数，用以控制数据源内加载的PreparedStatements数量。但由于预缓存的statements
属于单个connection而不是整个连接池。所以设置这个参数需要考虑到多方面的因素。
 如果maxStatements与maxStatementsPerConnection均为0，则缓存被关闭。Default: 0-->
<property name="maxStatements">100</property>

<!--maxStatementsPerConnection定义了连接池内单个连接所拥有的最大缓存statements数。Default: 0 -->
<property name="maxStatementsPerConnection"></property>

<!--c3p0是异步操作的，缓慢的JDBC操作通过帮助进程完成。扩展这些操作可以有效的提升性能
 通过多线程实现多个操作同时被执行。Default: 3-->
 <property name="numHelperThreads">3</property>

<!--当用户调用getConnection()时使root用户成为去获取连接的用户。主要用于连接池连接非c3p0
的数据源时。Default: null-->
<property name="overrideDefaultUser">root</property>

<!--与overrideDefaultUser参数对应使用的一个参数。Default: null-->
<property name="overrideDefaultPassword">password</property>

<!--密码。Default: null-->
<property name="password"></property>

<!--定义所有连接测试都执行的测试语句。在使用连接测试的情况下这个一显著提高测试速度。注意：
 测试的表必须在初始数据源的时候就存在。Default: null-->
 <property name="preferredTestQuery">select id from test where id=1</property>

<!--用户修改系统配置参数执行前最多等待300秒。Default: 300 -->
<property name="propertyCycle">300</property>

<!--因性能消耗大请只在需要的时候使用它。如果设为true那么在每个connection提交的
 时候都将校验其有效性。建议使用idleConnectionTestPeriod或automaticTestTable
等方法来提升连接测试的性能。Default: false -->
<property name="testConnectionOnCheckout">false</property>

<!--如果设为true那么在取得连接的同时将校验连接的有效性。Default: false -->
<property name="testConnectionOnCheckin">true</property>

<!--用户名。Default: null-->
<property name="user">root</property>

<!--早期的c3p0版本对JDBC接口采用动态反射代理。在早期版本用途广泛的情况下这个参数
 允许用户恢复到动态反射代理以解决不稳定的故障。最新的非反射代理更快并且已经开始
 广泛的被使用，所以这个参数未必有用。现在原先的动态反射与新的非反射代理同时受到
 支持，但今后可能的版本可能不支持动态反射代理。Default: false-->
<property name="usesTraditionalReflectiveProxies">false</property>

 <property name="automaticTestTable">con_test</property>
 <property name="checkoutTimeout">30000</property>
 <property name="idleConnectionTestPeriod">30</property>
 <property name="initialPoolSize">10</property>
 <property name="maxIdleTime">30</property>
 <property name="maxPoolSize">25</property>
 <property name="minPoolSize">10</property>
 <property name="maxStatements">0</property>
 <user-overrides user="swaldman">
 </user-overrides>
 </default-config>
 <named-config name="dumbTestConfig">
 <property name="maxStatements">200</property>
 <user-overrides user="poop">
 <property name="maxStatements">300</property>
 </user-overrides>
 </named-config>
 </c3p0-config>