黑马day11 c3p0数据库连接池

c3p0数据库连接池：我们以后开发就使用这个数据库连接池，非常的方便。只需要一个配置文件即可，c3p0默认是在类字节码文件中找到c3p0-config.xml文件。

使用步骤：

1.导入相应的jar包即可

2.然后再类中使用

案例1：

package com.itheima.c3p0;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import com.mchange.v2.c3p0.ComboPooledDataSource;public class C3P0Demo1 {public static void main(String[] args) {Connection con = null;PreparedStatement ps = null;ResultSet rs = null;try{//方式1:ComboPooledDataSource dataSource=new ComboPooledDataSource();dataSource.setDriverClass("com.mysql.jdbc.Driver");dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/day11");dataSource.setUser("root");dataSource.setPassword("169500");con=dataSource.getConnection();ps = con.prepareStatement("select * from account");rs = ps.executeQuery();while (rs.next()) {String name = rs.getString("name");System.out.println(name);}} catch (Exception e) {e.printStackTrace();throw new RuntimeException();} finally {if (rs != null) {try {rs.close();} catch (SQLException e) {e.printStackTrace();} finally {rs = null;}}if (ps != null) {try {ps.close();} catch (SQLException e) {e.printStackTrace();} finally {ps = null;}}if (con != null) {try {con.close();} catch (SQLException e) {e.printStackTrace();} finally {con = null;}}}}}方式二：在src目录下建立一个配置文件名为c3p0-config.xml文件，使用c3p0数据库连接池的类会自动找到在类字节码文件的这个配置文件：

配置如下：

<?xml version="1.0" encoding="UTF-8"?><c3p0-config> <default-config><property name="driverClass">com.mysql.jdbc.Driver</property><property name="jdbcUrl">jdbc:mysql://localhost:3306/day11</property><property name="user">root</property><property name="password">169500</property> </default-config></c3p0-config>在类中使用：

package com.itheima.c3p0;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import com.mchange.v2.c3p0.ComboPooledDataSource;public class C3P0Demo2 {public static void main(String[] args) {Connection con = null;PreparedStatement ps = null;ResultSet rs = null;try{//方式1:ComboPooledDataSource dataSource=new ComboPooledDataSource();//会默认寻找配置文件con=dataSource.getConnection();ps = con.prepareStatement("select * from account");rs = ps.executeQuery();while (rs.next()) {String name = rs.getString("name");System.out.println(name);}} catch (Exception e) {e.printStackTrace();throw new RuntimeException();} finally {if (rs != null) {try {rs.close();} catch (SQLException e) {e.printStackTrace();} finally {rs = null;}}if (ps != null) {try {ps.close();} catch (SQLException e) {e.printStackTrace();} finally {ps = null;}}if (con != null) {try {con.close();} catch (SQLException e) {e.printStackTrace();} finally {con = null;}}}}}运行结果：

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