Properties props = new Properties();

InputStream in = ConnectionManager.class.getResourceAsStream("/c3p0.properties");

props.load(in);

in.close();

ComboPooledDataSource cpds = new ComboPooledDataSource();
cpds.setDriverClass(props.getProperty("driverClass"));
cpds.setJdbcUrl(props.getProperty("jdbcUrl"));
cpds.setUser(props.getProperty("user"));
cpds.setPassword(props.getProperty("password"));

c3p0.driverClass=com.mysql.jdbc.Driver
c3p0.jdbcUrl=jdbc:mysql://localhost:3306/jdbc
c3p0.user=root
c3p0.password=java

private static ComboPooledDataSource ds = new ComboPooledDataSource();

public static Connection getConnection() {

 try {
 return ds.getConnection();
 } catch (SQLException e) {
 throw new RuntimeException(e);
 }

}

<c3p0-config>
 <default-config> 

 <property name="user">root</property>
 <property name="password">java</property>
 <property name="driverClass">com.mysql.jdbc.Driver</property>
 <property name="jdbcUrl">jdbc:mysql://localhost:3306/jdbc</property>
 <property name="initialPoolSize">10</property>
 <property name="maxIdleTime">30</property>
 <property name="maxPoolSize">100</property>
 <property name="minPoolSize">10</property>
 </default-config>

 <named-config name="myApp">
 <property name="user">root</property>
 <property name="password">java</property>
 <property name="driverClass">com.mysql.jdbc.Driver</property>
 <property name="jdbcUrl">jdbc:mysql://localhost:3306/jdbc</property>
 <property name="initialPoolSize">10</property>
 <property name="maxIdleTime">30</property>
 <property name="maxPoolSize">100</property>
 <property name="minPoolSize">10</property>

 </named-config>

</c3p0-config>

import java.sql.Connection;
import com.mchange.v2.c3p0.AbstractConnectionCustomizer;

public class ConnectionCustomizer extends AbstractConnectionCustomizer{

 @Override
 public void onAcquire(Connection c, String parentDataSourceIdentityToken)
   throws Exception {
  System.out.println("acquire : " + c);
 }
 @Override
 public void onCheckIn(Connection c, String parentDataSourceIdentityToken)
   throws Exception {
  System.out.println("checkin : " + c);
 }
 @Override
 public void onCheckOut(Connection c, String parentDataSourceIdentityToken)
   throws Exception {
  System.out.println("checkout : " + c);
 }
 @Override

 public void onDestroy(Connection c, String parentDataSourceIdentityToken)

   throws Exception {

  System.out.println("destroy : " + c);

 }

}

<property name="connectionCustomizerClassName">liuyun.zhuge.db.ConnectionCustomizer</property>

#驱动 
c3p0.driverClass=com.mysql.jdbc.Driver 
#地址 
c3p0.jdbcUrl=jdbc:mysql://localhost:3306/jdbc 
#用户名 
c3p0.user=root 
#密码 
c3p0.password=lovejava 
#------------------------------- 
#连接池初始化时创建的连接数 
c3p0.initialPoolSize=3 
#连接池保持的最小连接数 
c3p0.minPoolSize=3 
#连接池在无空闲连接可用时一次性创建的新数据库连接数,default:3 
c3p0.acquireIncrement=3 
#连接池中拥有的最大连接数，如果获得新连接时会使连接总数超过这个值则不会再获取新连接，而是等待其他连接释放，所以这个值有可能会设计地很大,default : 15 
c3p0.maxPoolSize=15 
#连接的最大空闲时间，如果超过这个时间，某个数据库连接还没有被使用，则会断开掉这个连接,单位秒 
c3p0.maxIdleTime=100 
#连接池在获得新连接失败时重试的次数，如果小于等于0则无限重试直至连接获得成功 
c3p0.acquireRetryAttempts=30 
#连接池在获得新连接时的间隔时间 
c3p0.acquireRetryDelay=1000

package com.study.pool; 
 
import java.sql.Connection; 
import java.sql.SQLException; 
 
import javax.sql.DataSource; 
 
import com.mchange.v2.c3p0.ComboPooledDataSource; 
 
public class ConnectionPool { 
 private DataSource ds; 
 private static ConnectionPool pool; 
 private ConnectionPool(){ 
  ds = new ComboPooledDataSource(); 
 } 
 public static final ConnectionPool getInstance(){ 
  if(pool==null){ 
   try{ 
    pool = new ConnectionPool(); 
   }catch (Exception e) { 
    e.printStackTrace(); 
   } 
  } 
  return pool; 
 } 
 public synchronized final Connection getConnection() { 
  try { 
   return ds.getConnection(); 
  } catch (SQLException e) {  
   e.printStackTrace(); 
  } 
  return null; 
 } 
  
}

package com.study.pool; 
 
import java.sql.Connection; 
import java.sql.PreparedStatement; 
import java.sql.ResultSet; 
import java.sql.SQLException; 
 
public class PoolThread extends Thread { 
 @Override 
 public void run(){ 
  ConnectionPool pool = ConnectionPool.getInstance(); 
  Connection con = null; 
  PreparedStatement stmt= null; 
  ResultSet rs = null; 
  try{ 
   con = pool.getConnection(); 
   stmt = con.prepareStatement("select sysdate as nowtime from dual"); 
   rs = stmt.executeQuery(); 
   while(rs.next()){ 
    System.out.println(Thread.currentThread().getId()+"---------------开始"+rs.getString("nowtime")); 
   } 
  } catch (Exception e) { 
   e.printStackTrace(); 
  }finally{ 
   try { 
    rs.close(); 
    stmt.close(); 
    con.close(); 
   } catch (SQLException e) { 
    e.printStackTrace(); 
   } 
  } 
  System.out.println(Thread.currentThread().getId()+"--------结束"); 
 } 
}

package com.study.pool; 
 
public class PoolMain { 
 
 /** 
  * 数据源缓冲池 实例练习 
  */ 
 public static void main(String[] args) { 
  System.out.println("缓冲池模拟开始"); 
  PoolThread[] threads = new PoolThread[50]; 
  for(int i=0;i<threads.length;i++){ 
   threads[i] = new PoolThread(); 
  } 
  for(int i=0;i<threads.length;i++){ 
   threads[i].start(); 
  } 
 } 
 
}