package com.qfedu.c3p0;
import java.beans.PropertyVetoException;
import java.sql.Connection;
import java.sql.SQLException;
import com.mchange.v2.c3p0.ComboPooledDataSource;
public class App {
  public static void main(String[] args) throws Exception {
    // TODO Auto-generated method stub
//    test1();
    test2();
  }
  public static void test1() throws Exception {
    // 创建c3p0的数据库池连接对象
    ComboPooledDataSource dataSource = new ComboPooledDataSource();
    // 配置
    dataSource.setDriverClass("com.mysql.cj.jdbc.Driver");
    dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/db2210?serverTimezone=Asia/Shanghai&useSSL=false");
    dataSource.setUser("root");
    dataSource.setPassword("root");
    // 初始连接数
    dataSource.setInitialPoolSize(3);
    // 最大连接数
    dataSource.setMaxPoolSize(10);
    // 最大空闲时间，单位毫秒
    dataSource.setMaxIdleTime(2000);
    // 通过连接池获取连接对象
    Connection connection = dataSource.getConnection();
    System.out.println(connection);
    // 将连接对象还回连接池
    connection.close();
  }
  /**
   * 读取c3p0的配置文件
   * 正常的url jdbc:mysql://localhost:3306/db2210?serverTimezone=Asia/Shanghai&useSSL=false
   * &在xml中属于特殊符号，所以在xml中需要使用 实体符号 &替换
   * <property name="jdbcUrl">jdbc:mysql://localhost:3306/db2210?serverTimezone=Asia/Shanghai&amp;userSSL=false</property>
   * 
   * @throws Exception
   */
  public static void test2() throws Exception {
    // 自动读取src下的c3p0-config.xml
    // 默认加载<default-config>中的配置
    ComboPooledDataSource dataSource = new ComboPooledDataSource();
    // 获取连接对象
    Connection connection = dataSource.getConnection();
    System.out.println(connection);
    // “关闭”连接对象，将连接对象还回连接池
    connection.close();
  }
}

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
  <default-config>
     <property name="driverClass">com.mysql.cj.jdbc.Driver</property>
     <property name="jdbcUrl">jdbc:mysql://localhost:3306/db2210?serverTimezone=Asia/Shanghai&amp;useSSL=false</property>
     <property name="user">root</property>
     <property name="password">root</property>
     <property name="initialPoolSize">3</property>
     <property name="maxPoolSize">6</property>
     <property name="maxIdleTime">2000</property>
  </default-config>
  <named-config name="myconfig">
     <property name="driverClass">com.mysql.jdbc.Driver</property>
     <property name="jdbcUrl">jdbc:mysql:///supermarket</property>
     <property name="user">root</property>
     <property name="password">root</property>
     <property name="initialPoolSize">3</property>
     <property name="maxPoolSize">6</property>
     <property name="maxIdleTime">2000</property>
  </named-config>
</c3p0-config>

package com.qfedu.utils;
import org.apache.commons.dbutils.QueryRunner;
import com.mchange.v2.c3p0.ComboPooledDataSource;
public class C3P0Utils {
  // ComboPooledDataSource 实现 jdbc中的DataSource接口
  private static ComboPooledDataSource dataSource = null;
  // 创建连接池对象
  static {
    dataSource = new ComboPooledDataSource();
  }
  public static QueryRunner getQueryRunner() {
    // javax.sql.DataSource
    // QueryRunner(DataSource ds)
    // 将DBUtils和数据库连接池产生了关联
    // QueryRunner内部维护连接对象
    return new QueryRunner(dataSource);
  }
}

public static void test2() throws Exception {
    QueryRunner qr = C3P0Utils.getQueryRunner();
    String sql = "select count(*) from t_person";
    // QueryRunner内部维护连接对象，调用query,不需要connection参数
    // 执行完，也不需要手动关闭connection对象
    Long count = qr.query(sql, new ScalarHandler<Long>());
    System.out.println(count);
  }

package com.qfedu.druid;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;
import javax.sql.DataSource;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.ScalarHandler;
import com.alibaba.druid.pool.DruidDataSourceFactory;
import com.qfedu.utils.DruidUtils;
public class App {
  public static void main(String[] args) throws Exception {
    // TODO Auto-generated method stub
//    test1();
    test2();
  }
  public static void test1() throws Exception {
    // 通过Properties加载properties文件中内容
    FileInputStream inputStream = new FileInputStream("src/druid.properties");
    Properties prop = new Properties();
    prop.load(inputStream);
    // 获取连接池对象
    // javax.sql.DataSource
    DataSource dataSource = DruidDataSourceFactory.createDataSource(prop);
    Connection connection = dataSource.getConnection();
    System.out.println(connection);
    connection.close();
  }
  public static void test2() throws Exception {
    QueryRunner queryRunner = DruidUtils.getQueryRunner();
    String sql = "select count(*) from t_person";
    Long count = queryRunner.query(sql, new ScalarHandler<Long>());
    System.out.println(count);
  }
}

# \u6587\u4EF6\u540D druid.properties \u5B58\u50A8\u5728src\u76EE\u5F55\u4E0B
driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/db2210?serverTimezone=Asia/Shanghai&useSSL=true
username=root
password=root
# \u521D\u59CB\u5316\u6570\u636E\u5E93\u8FDE\u63A5\u6C60\u4E2D\u8FDE\u63A5\u4E2A\u6570
initialSize=5
# \u6700\u5927\u4E2A\u6570
maxActive=20
# TimeOut \u7B49\u5F85\u8D85\u65F6\u65F6\u95F4
maxWait=2000

package com.qfedu.utils;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.util.Properties;
import javax.sql.DataSource;
import org.apache.commons.dbutils.QueryRunner;
import com.alibaba.druid.pool.DruidDataSourceFactory;
public class DruidUtils {
  private static DataSource dataSource = null;
  static {
    try {
      FileInputStream inputStream = new FileInputStream("src/druid.properties");
      Properties prop = new Properties();
      prop.load(inputStream);
      // 创建连接池对象
      dataSource = DruidDataSourceFactory.createDataSource(prop);
    } catch (Exception e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
  }
  /**
   * 创建QueryRunner对象，一定要注意，参数使用连接池对象
   * @return
   */
  public static QueryRunner getQueryRunner() {
    return new QueryRunner(dataSource);
  }
}