连接池DBCP、C3P0、Druid(德鲁伊)和dbutils

连接池

负责分配，管理，释放数据库连接，允许应用程序重复实验一个现有的数据库连接。

以下代码中所用到的jar包和配置文件，此处下载

以下连接池都是在以查询表users(username,password)为例

DBCP方式:

先添加jar包
再依赖于项目

• 硬编码方式 （用户名密码等自己写）
  代码：

package com.jingfei.connectionpool;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import org.apache.commons.dbcp.BasicDataSource;

public class DBCPtest {
	public static void main(String[] args) throws Exception {
		// 创建连接池对象
		BasicDataSource dSource = new BasicDataSource();
		// 连接本机的mydb库
		String url = "jdbc:mysql://localhost:3306/mydb";
		String username = "root";
		String password = "123456";
		String driverClassName = "com.mysql.jdbc.Driver";
		dSource.setUrl(url);
		dSource.setUsername(username);
		dSource.setPassword(password);
		dSource.setDriverClassName(driverClassName);
		//获取连接对象
		Connection connection = dSource.getConnection();
		//查询表users(username,password)
		String sql="select * from users";
		PreparedStatement statement=connection.prepareStatement(sql);
		ResultSet resultSet=statement.executeQuery();
		//遍历返回的结果集
		while(resultSet.next()){
			String name=resultSet.getString(1);
			String pwd=resultSet.getString(2);
			System.out.println(name+"=="+pwd);
		}
		statement.close();
		connection.close();
	}
}

• 配置文件方式
  将dbcp.properties文件放在src目录下
  
  代码

package com.jingfei.connectionpool;

import java.io.FileInputStream;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;

import javax.sql.DataSource;

import org.apache.commons.dbcp.BasicDataSource;
import org.apache.commons.dbcp.BasicDataSourceFactory;

public class DBCPtest {
	public static void main(String[] args) throws Exception {
		//将dbcp.properties文件放在src目录下
		// 创建属性集合关联配置文件
		Properties properties=new Properties();
		properties.load(new FileInputStream("src/dbcp.properties"));
		// 创建连接池对象
		DataSource dSource= new BasicDataSourceFactory().createDataSource(properties);
		//获取连接对象
		Connection connection = dSource.getConnection();
		//查询表users(username,password)
		String sql="select * from users";
		PreparedStatement statement=connection.prepareStatement(sql);
		ResultSet resultSet=statement.executeQuery();
		while(resultSet.next()){
			String name=resultSet.getString(1);
			String pwd=resultSet.getString(2);
			System.out.println(name+"=="+pwd);
		}
		statement.close();
		connection.close();
	}
}

---

C3P0方式
和上述dbcp基本一样
先添加jar包
再依赖于项目

• 硬编码方式

代码

package com.jingfei.connectionpool;

import java.beans.PropertyVetoException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class C3P0test {
	public static void main(String[] args) throws Exception {
		ComboPooledDataSource dSource = new ComboPooledDataSource();
		String url = "jdbc:mysql://localhost:3306/mydb";
		String username = "root";
		String password = "123456";
		String driverClassName = "com.mysql.jdbc.Driver";
		dSource.setJdbcUrl(url);
		dSource.setUser(username);
		dSource.setPassword(password);
		dSource.setDriverClass(driverClassName);
		// 获取连接对象
		Connection connection = dSource.getConnection();
		// 查询表users(username,password)
		String sql = "select * from users";
		PreparedStatement statement = connection.prepareStatement(sql);
		ResultSet resultSet = statement.executeQuery();
		// 遍历返回的结果集
		while (resultSet.next()) {
			String name = resultSet.getString(1);
			String pwd = resultSet.getString(2);
			System.out.println(name + "==" + pwd);
		}
		statement.close();
	}
}

• 配置文件方式
  要求配置文件文件名不能改
  要求配置文件必须放在src目录下
  
  代码：

package com.jingfei.connectionpool;

import java.beans.PropertyVetoException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class C3P0test2 {
	public static void main(String[] args) throws Exception {
		//获取连接池对象
		ComboPooledDataSource dSource = new ComboPooledDataSource();
		// 获取连接对象，此时因为有配置文件（文件中存有用户名密码等），所以可以直接获取
		Connection connection = dSource.getConnection();
		// 查询表users(username,password)
		String sql = "select * from users";
		PreparedStatement statement = connection.prepareStatement(sql);
		ResultSet resultSet = statement.executeQuery();
		// 遍历返回的结果集
		while (resultSet.next()) {
			String name = resultSet.getString(1);
			String pwd = resultSet.getString(2);
			System.out.println(name + "==" + pwd);
		}
		statement.close();
	}
}

---

Druid方式（德鲁伊）
号称史上最强的连接池，阿里开发，开源
详细介绍1
详细介绍2

还上述基本一样
先添加jar包
再依赖于项目

• 硬编码方式
  代码

package com.jingfei.connectionpool;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import com.alibaba.druid.pool.DruidDataSource;

public class Druidtest {
	public static void main(String[] args) throws Exception {
		// 获取连接池对象
		DruidDataSource dSource = new DruidDataSource();
		String url = "jdbc:mysql://localhost:3306/mydb";
		String username = "root";
		String password = "123456";
		String driverClassName = "com.mysql.jdbc.Driver";
		dSource.setUrl(url);
		dSource.setUsername(username);
		dSource.setPassword(password);
		dSource.setDriverClassName(driverClassName);
		// 获取连接对象
		Connection connection = dSource.getConnection();
		// 查询表users(username,password)
		String sql = "select * from users";
		PreparedStatement statement = connection.prepareStatement(sql);
		ResultSet resultSet = statement.executeQuery();
		// 遍历返回的结果集
		while (resultSet.next()) {
			String name = resultSet.getString(1);
			String pwd = resultSet.getString(2);
			System.out.println(name + "==" + pwd);
		}
		statement.close();
		connection.close();
	}
}

• 配置文件方式
  配置文件随便放，为了统一起见放在src目录下，用属性集合Properties关联
  代码

package com.jingfei.connectionpool;

import java.io.FileInputStream;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.Properties;

import com.alibaba.druid.pool.DruidDataSource;

public class Druidtest2 {
	public static void main(String[] args) throws Exception {
		// 获取连接池对象
		DruidDataSource dSource = new DruidDataSource();
		//属性集合并关联配置文件，并读取里面的值
		Properties properties = new Properties();
		properties.load(new FileInputStream("src/db_server.properties"));
		String url = properties.getProperty("url");
		String username = properties.getProperty("username");
		String password = properties.getProperty("password");
		String driverClassName = properties.getProperty("driverClassName");
		dSource.setUrl(url);
		dSource.setUsername(username);
		dSource.setPassword(password);
		dSource.setDriverClassName(driverClassName);
		// 获取连接对象
		Connection connection = dSource.getConnection();
		// 查询表users(username,password)
		String sql = "select * from users";
		PreparedStatement statement = connection.prepareStatement(sql);
		ResultSet resultSet = statement.executeQuery();
		// 遍历返回的结果集
		while (resultSet.next()) {
			String name = resultSet.getString(1);
			String pwd = resultSet.getString(2);
			System.out.println(name + "==" + pwd);
		}
		statement.close();
		connection.close();
	}
}

结果都为原来存在表中的所有数据

张三==123456
赵六==654321
赵七==654321
bob==123456

---

dbutils

Commons DbUtils是Apache组织提供的一个对JDBC进行简单封装的开源工具类库，使用它能够简化JDBC应用程序的开发，同时也不会影响程序的性能。

导入jar包，依赖项目
代码

package com.jingfei.connectionpool;

import java.io.FileInputStream;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import javax.sql.DataSource;
import org.apache.commons.dbcp.BasicDataSourceFactory;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.MapListHandler;

public class DButils {
	public static void main(String[] args) throws Exception {
		// 将dbcp.properties文件放在src目录下
		// 创建属性集合关联配置文件
		Properties properties = new Properties();
		properties.load(new FileInputStream("src/dbcp.properties"));
		// 创建连接池对象
		DataSource dSource = new BasicDataSourceFactory().createDataSource(properties);
		QueryRunner queryRunner = new QueryRunner(dSource);
		String sql = "select * from users";
		//逐行打印new MapListHandler()
		List<Map<String, Object>> list= queryRunner.query(sql, new MapListHandler());
		for(Map<String, Object> map:list){
			String username=(String) map.get("username");
			String password=(String) map.get("password");
			System.out.println(username+"=="+password);
		}
		//如果想封装到Users对象中(两个属性username，password,提供getter|setter方法)，
		//那就用new BeanListHandler<Users>(Users.class)
		List<Users> list1=queryRunner.query(sql, new BeanListHandler<Users>(Users.class));
		System.out.println(list1);
	}

}

若增改查，可以直接传值：

		//插入更新数据,可直接传值。
		String sql = "insert into users values(?,?)";
		queryRunner.update(sql,"马云","123456");

下面是handler参数和返回对象类型的对照表:

• AbstractListHandler – 返回多行List的抽象类

• ArrayHandler – 返回一行的Object[]

• ArrayListHandler – 返回List，每行是Object[]

• BeanHandler – 返回第一个Bean对象

• BeanListHandler – 返回List，每行是Bean对象

• ColumnListHandler – 返回一列的List

• KeyedHandler – 返回Map，具体见代码

• MapHandler – 返回单个Map

• MapListHandler – 返回List，每行是Map

• ScalarHandler – 返回列的头一个值

---

谢谢！