JavaWeb6.1【数据库连接池、C3P0数据库连接池技术】

 

 

package com.haifei.datasource.c3p0;

import com.mchange.v2.c3p0.ComboPooledDataSource;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.SQLException;

/*
数据库连接池

    1. 概念：其实就是一个容器(集合)，存放数据库连接的容器。
            当系统初始化好后，容器被创建，容器中会申请一些连接对象，当用户来访问数据库时，从容器中获取连接对象，用户访问完之后，会将连接对象归还给容器。

    2. 好处：
        1. 节约资源
        2. 用户访问高效

    3. 实现：
        1. 标准接口：DataSource   javax.sql包下的
            1. 方法：
                * 获取连接：getConnection()
                * 归还连接：Connection.close()。如果连接对象Connection是从连接池中获取的，那么调用Connection.close()方法，则不会再关闭连接了。而是归还连接

        2. 一般我们不去实现它，有数据库厂商来实现
            1. C3P0：数据库连接池技术
            2. Druid：数据库连接池实现技术，由阿里巴巴提供的

    4. C3P0：数据库连接池技术
        1. 导入jar包 (两个) c3p0-0.9.5.2.jar  和  mchange-commons-java-0.2.12.jar ，
            * 不要忘记导入数据库驱动jar包mysql-connector-java-5.1.37-bin.jar
            * 即一共所需3个jar包
        2. 定义配置文件：
            * 名称： c3p0.properties 或者 c3p0-config.xml
            * 路径：直接将文件放在src目录下即可。

        3. 创建核心对象 数据库连接池对象 ComboPooledDataSource
        4. 获取连接： getConnection
 */
public class C3P0Demo1 {
    public static void main(String[] args) throws SQLException {
        //1 创建数据库连接池对象
        DataSource ds = new ComboPooledDataSource();

        //2 获取连接对象
        Connection conn = ds.getConnection();
        System.out.println(conn); //com.mchange.v2.c3p0.impl.NewProxyConnection@550ee7e5 [wrapping: com.mysql.jdbc.JDBC4Connection@5f9b2141]


    }
}

package com.haifei.datasource.c3p0;

import com.mchange.v2.c3p0.ComboPooledDataSource;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.SQLException;

public class C3P0Demo2 {
    public static void main(String[] args) throws SQLException {
//        testDefaultConfig();
        testNamedConfig();
    }


    public static void testDefaultConfig() throws SQLException{
        //获取数据库连接池对象，使用默认配置<default-config>
        DataSource ds = new ComboPooledDataSource();

//        for (int i=1; i<=10; i++){
        for (int i=1; i<=11; i++){
            Connection conn = ds.getConnection();
            System.out.println(i + ":" + conn);

            /*if(i == 5){
                conn.close(); //#11号之前#5提前主动归还连接对象
            }*/
        }

        /*
        1:com.mchange.v2.c3p0.impl.NewProxyConnection@3514a4c0 [wrapping: com.mysql.jdbc.JDBC4Connection@212b5695]
        2:com.mchange.v2.c3p0.impl.NewProxyConnection@69997e9d [wrapping: com.mysql.jdbc.JDBC4Connection@793be5ca]
        3:com.mchange.v2.c3p0.impl.NewProxyConnection@37654521 [wrapping: com.mysql.jdbc.JDBC4Connection@15aab8c6]
        4:com.mchange.v2.c3p0.impl.NewProxyConnection@4de4b452 [wrapping: com.mysql.jdbc.JDBC4Connection@50b5ac82]
        5:com.mchange.v2.c3p0.impl.NewProxyConnection@6babf3bf [wrapping: com.mysql.jdbc.JDBC4Connection@3059cbc]
        6:com.mchange.v2.c3p0.impl.NewProxyConnection@24fcf36f [wrapping: com.mysql.jdbc.JDBC4Connection@10feca44]
        7:com.mchange.v2.c3p0.impl.NewProxyConnection@ea6147e [wrapping: com.mysql.jdbc.JDBC4Connection@4d02f94e]
        8:com.mchange.v2.c3p0.impl.NewProxyConnection@1e683a3e [wrapping: com.mysql.jdbc.JDBC4Connection@2053d869]
        9:com.mchange.v2.c3p0.impl.NewProxyConnection@14555e0a [wrapping: com.mysql.jdbc.JDBC4Connection@4bb33f74]
        10:com.mchange.v2.c3p0.impl.NewProxyConnection@3c73951 [wrapping: com.mysql.jdbc.JDBC4Connection@3d5c822d]

        //Exception in thread "main" java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.
         */
    }


    public static void testNamedConfig() throws SQLException{
        //获取数据库连接池对象，使用指定配置<named-config name="otherc3p0">
        DataSource ds = new ComboPooledDataSource("otherc3p0");

        for (int i=1; i<=10; i++){
            Connection conn = ds.getConnection();
            System.out.println(i + ":" + conn);
        }

        /*
        1:com.mchange.v2.c3p0.impl.NewProxyConnection@6bedbc4d [wrapping: com.mysql.jdbc.JDBC4Connection@932bc4a]
        2:com.mchange.v2.c3p0.impl.NewProxyConnection@2fd1433e [wrapping: com.mysql.jdbc.JDBC4Connection@29d89d5d]
        3:com.mchange.v2.c3p0.impl.NewProxyConnection@212b5695 [wrapping: com.mysql.jdbc.JDBC4Connection@446293d]
        4:com.mchange.v2.c3p0.impl.NewProxyConnection@793be5ca [wrapping: com.mysql.jdbc.JDBC4Connection@2df9b86]
        5:com.mchange.v2.c3p0.impl.NewProxyConnection@15aab8c6 [wrapping: com.mysql.jdbc.JDBC4Connection@33990a0c]
        6:com.mchange.v2.c3p0.impl.NewProxyConnection@50b5ac82 [wrapping: com.mysql.jdbc.JDBC4Connection@101952da]
        7:com.mchange.v2.c3p0.impl.NewProxyConnection@3059cbc [wrapping: com.mysql.jdbc.JDBC4Connection@7ea9e1e2]
        8:com.mchange.v2.c3p0.impl.NewProxyConnection@10feca44 [wrapping: com.mysql.jdbc.JDBC4Connection@3fb1549b]

        Exception in thread "main" java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.
         */
    }


}

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<c3p0-config>   <!-- 使用默认的配置读取连接池对象 -->   <default-config>     <!--  连接参数 -->     <property name="driverClass">com.mysql.jdbc.Driver</property>     <property name="jdbcUrl">jdbc:mysql://localhost:3306/hm_db2</property>     <property name="user">root</property>     <property name="password">root</property>           <!-- 连接池参数 -->     <property name="initialPoolSize">5</property><!-- 初始化申请的连接数量 -->     <property name="maxPoolSize">10</property><!-- 最大的连接数量 -->     <property name="checkoutTimeout">3000</property><!-- 超时时间 -->   </default-config>     <named-config name="otherc3p0">     <!--  连接参数 -->     <property name="driverClass">com.mysql.jdbc.Driver</property>     <property name="jdbcUrl">jdbc:mysql://localhost:3306/hm_db2</property>     <property name="user">root</property>     <property name="password">root</property>           <!-- 连接池参数 -->     <property name="initialPoolSize">5</property>     <property name="maxPoolSize">8</property>     <property name="checkoutTimeout">1000</property>   </named-config> </c3p0-config>