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

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！

com.mysql.jdbc.Driver <![CDATA[jdbc:mysql://127.0.0.1:3306/hncu?useUnicode=true&characterEncoding=UTF-8]]> root 1234 2 30 10 2 50 com.mysql.jdbc.Driver <![CDATA[jdbc:mysql://127.0.0.1:3306/hncu?useUnicode=true&characterEncoding=UTF-8]]> root 1234 5 100 50 1000 0 5

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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());
}
}

}
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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 t = new ThreadLocal();
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;
}