MySQL---数据库从入门走向大神系列(十四)-ComboPooledDataSource(C3P0连接池配置)

From:http://blog.csdn.net/qq_26525215/article/details/52212260需要准备的jar包：MySQL的jar包mysql-connector-Java-5.1.39-bin目前是5.1.39版本：http://dev.mysql.com/downloads/connector/j/C3p0的2个包：https://sourceforge.net/projects/c3p0/c3p0-0.9.1.2.jar和c3p0-sources-0.9.1.2.jar配置文件：c3p0-config.xml名字必须为这个！

<c3p0-config>
<!-- 默认配置，如果没有指定则使用这个配置 -->
<default-config>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl">
<![CDATA[jdbc:mysql://127.0.0.1:3306/hncu?useUnicode=true&characterEncoding=UTF-8]]>
</property>
<property name="user">root</property>
<property name="password">1234</property>
<!-- 初始化池大小 -->
<property name="initialPoolSize">2</property>
<!-- 最大空闲时间 -->
<property name="maxIdleTime">30</property>
<!-- 最多有多少个连接 -->
<property name="maxPoolSize">10</property>
<!-- 最少几个连接 -->
<property name="minPoolSize">2</property>
<!-- 每次最多可以执行多少个批处理语句 -->
<property name="maxStatements">50</property>
</default-config>
<!-- 命名的配置 -->
<named-config name="demo">
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl"><![CDATA[jdbc:mysql://127.0.0.1:3306/hncu?useUnicode=true&characterEncoding=UTF-8]]></property>
<property name="user">root</property>
<property name="password">1234</property>
<property name="acquireIncrement">5</property><!-- 如果池中数据连接不够时一次增长多少个 -->
<property name="initialPoolSize">100</property>
<property name="minPoolSize">50</property>
<property name="maxPoolSize">1000</property>
<property name="maxStatements">0</property>
<property name="maxStatementsPerConnection">5</property> <!-- he's important, but there's only one of him -->
</named-config>
</c3p0-config>

演示代码：

package cn.hncu.C3p0;

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

import org.junit.Test;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class C3p0Demo {

@Test
// 纯Java方法使用c3p0
public void C3p0Demo() throws PropertyVetoException, SQLException {
ComboPooledDataSource pool = new ComboPooledDataSource();
pool.setUser("root");// 用户姓名
pool.setPassword("1234");// 用户密码
pool.setJdbcUrl("jdbc:mysql://127.0.0.1:3306/hncu?useUnicode=true&characterEncoding=utf-8");// MySQL数据库连接url
pool.setDriverClass("com.mysql.jdbc.Driver");

// pool可以调用set方法进行Connection池的配置

// 连接关闭之后，内存会被释放，下次取时会重新开(内存地址不共用)
for (int i = 0; i < 20; i++) {
Connection con = pool.getConnection();
System.out.println(i + ":" + con);
if (i % 2 == 0) {
con.close();
}
}
}

@Test
// 演示采用配置文件的方式使用c3p0
public void C3p0PropertyDemo() throws SQLException {
ComboPooledDataSource pool = new ComboPooledDataSource();//空参，自动到classpath目录下面加载“c3p0-config.xml”配置文件---配置文件的存储位置和名称必须是这样，且使用“默认配置”
//ComboPooledDataSource pool = new ComboPooledDataSource("demo");//加载“c3p0-config.xml”文件中定义的“demo”这个配置元素
for(int i=0;i<25;i++){
Connection con = pool.getConnection();
System.out.println(i+":"+ con.hashCode());
}
}

}

包装一下C3P0的Connection池

package cn.hncu.C3p0;

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

import javax.sql.DataSource;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class C3p0Pool {
//我们的这个包装，只是为了把c3p0池做成让每个线程(客户端)获得的是同一个连接，方便做b/s框架下的事务
private static DataSource pool;
private static ThreadLocal<Connection> t = new ThreadLocal<Connection>();
static{
pool = new ComboPooledDataSource("demo");
//这里的参数视你的配置文件而定，也可以不写，用默认的配置
}

public static DataSource getDataSource(){
return pool;
}

public static Connection getConnection() throws SQLException{
Connection con = t.get();
if(con==null){
con=pool.getConnection();
t.set(con);
}
return con;
}
}