c3p0连接池的用法

1、导入c3p0jar包

c3p0-0.9.1.2.jar

2、xml配置文件

在src的目录下, 创建一个名称为 c3p0-config.xml的配置文件, 配置信息如下:

1）最基本配置*四个连接数据库必须的参数）

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
    <default-config>
        <property name="driverClass">com.mysql.jdbc.Driver</property>
        <property name="jdbcUrl">jdbc:mysql://106.13.43.205:3306/test</property>
        <property name="user">root</property>
        <property name="password">aaaaa123</property>
    </default-config> 
</c3p0-config> 

2）复杂的配置信息

<?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/test</property>  
        <property name="user">root</property>  
        <property name="password">123456</property>  
             <!--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">5</property>  
             <!--初始化的连接数，取值应在minPoolSize与maxPoolSize之间。Default: 3-->  
        <property name="initialPoolSize">10</property>  
             <!--连接池中保留的最小连接数-->  
        <property name="minPoolSize">5</property>  
             <!--连接池中保留的最大连接数。Default:15 -->  
        <property name="maxPoolSize">20</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>  
    </default-config> 
</c3p0-config>

3、创建数据源DataSourceUtils（工具类）

package com.canghe.utils;

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

import javax.sql.DataSource;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class DataSourceUtils {

    private static DataSource dataSource = new ComboPooledDataSource();

    private static ThreadLocal<Connection> tl = new ThreadLocal<Connection>();

    // 直接可以获取一个连接池
    public static DataSource getDataSource() {
        return dataSource;
    }

    // 获取连接对象
    public static Connection getConnection() throws SQLException {

        Connection con = tl.get();
        if (con == null) {
            con = dataSource.getConnection();
            tl.set(con);
        }
        return con;
    }

    // 开启事务
    public static void startTransaction() throws SQLException {
        Connection con = getConnection();
        if (con != null) {
            con.setAutoCommit(false);
        }
    }

    // 事务回滚
    public static void rollback() throws SQLException {
        Connection con = getConnection();
        if (con != null) {
            con.rollback();
        }
    }

    // 提交并且 关闭资源及从ThreadLocall中释放
    public static void commitAndRelease() throws SQLException {
        Connection con = getConnection();
        if (con != null) {
            con.commit(); // 事务提交
            con.close();// 关闭资源
            tl.remove();// 从线程绑定中移除
        }
    }

    // 关闭资源方法
    public static void closeConnection() throws SQLException {
        Connection con = getConnection();
        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();
        }
    }

}

4、使用DButils进行连接并对数据库进行操作

QueryRunner runner = new QueryRunner(DataSourceUtils.getDataSource());
        String sql = "select * from product";
        List<Product> productList = null;
        try {
            productList = runner.query(sql, new BeanListHandler<Product>(Product.class));
        } catch (SQLException e) {
            e.printStackTrace();
        }