各连接池需要的jar包

• DBCP
  commons-dbcp-1.4.jar
  commons-pool-1.5.5.jar
• C3P0
  c3p0-0.9.1.2.jar
• Druid
  druid-1.1.10.jar

package csdn1;

import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;
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.ScalarHandler;
import org.junit.Test;

import com.alibaba.druid.pool.DruidDataSourceFactory;
import com.mchange.v2.c3p0.ComboPooledDataSource;

//2.使用现有的数据库连接池

public class jdbc7 {
	// 2.1各个连接池获取连接的方式

	// DBCP--需导入两个commons-dbcp-1.4.jar和commons-pool-1.5.5.jar
	@Test
	public void dbcp() throws Exception {
		/*
		 * BasicDataSource bds = new BasicDataSource();
		 * bds.setDriverClassName("com.mysql.jdbc.Driver");
		 * bds.setUrl("jdbc:mysql:///mydbs2"); bds.setUsername("root");
		 * bds.setPassword("root"); Connection cn = bds.getConnection();
		 */
		// 更多的是使用配置文件的方式来配置参数--包括其它连接池也一样
		Properties p = new Properties();
		FileInputStream inputStream = new FileInputStream(new File("src/csdn1/dbcp.properties"));//配置文件内容和位置在文末
		p.load(inputStream);
		DataSource ds = BasicDataSourceFactory.createDataSource(p);// 需导入源码commons-dbcp-1.4-src.zip
		Connection cn = ds.getConnection();
		System.out.println(cn);
	}

	// Druid--需导入druid-1.1.10.jar---德鲁伊数据库连接池
	@Test
	public void druid() throws Exception {
		Properties p = new Properties();
		FileInputStream inputStream = new FileInputStream(new File("src/csdn1/druid.properties"));//配置文件内容和位置在文末
		p.load(inputStream);
		DataSource ds = DruidDataSourceFactory.createDataSource(p);
		Connection cn = ds.getConnection();
		System.out.println(cn);
	}

	// C3P0--需导入c3p0-0.9.1.2.jar
	// 稍有不同的是配置文件变为位于src下的c3p0-config.xml文件，配置文件内容和位置在文末
	@Test
	public void c3p0() throws SQLException {
		ComboPooledDataSource ds = new ComboPooledDataSource("xmlName");
		Connection cn = ds.getConnection();
		System.out.println(cn);
	}

	// 2.2实操--需导入commons.dbutils(开源jdbc类库)，实现增删改查--下面的连接获取均使用druid数据库连接池
	// 增删改
	// update(Connection conn, String sql, Object... params)
	@Test
	public void update() {
		QueryRunner query = new QueryRunner();
		try (Connection druidConnection = JDBCUtils.getDruidConnection();) {
			String sql = "insert into user (name,password) values(?,?)";
			query.update(druidConnection, sql, "ming", "ming123");
			sql = "update user set password=? where name=?";
			int effect = query.update(druidConnection, sql, "mdzone", "ming");
			System.out.println("返回影响的记录数：" + effect);
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}

	// 查询query()
	/*
	 * 用于封装表中的记录--都是实现ResultHandler接口 
	 * 处理对象：BeanHandler,BeanListHandler
	 * 键值对处理：MapHandler 
	 * 聚集函数查询处理：ScalarHandler
	 * 
	 */
	@Test
	public void query() {
		QueryRunner qr = new QueryRunner();
		try (Connection druidConnection = JDBCUtils.getDruidConnection();) {
			String sql = "select count(*) from user;";
			ScalarHandler handler = new ScalarHandler();
			Long count = (Long) qr.query(druidConnection, sql, handler);
			System.out.println(count);

			sql = "select id,name,password from user;";
			BeanListHandler<User> beanList = new BeanListHandler<>(User.class);
			List<User> query = qr.query(druidConnection, sql, beanList);
			for(User u :query) {
				System.out.println(u);
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
}
//获取连接的类JDBCUtils
class JDBCUtils {
	// druid
	private static DataSource druid = null;
	static {
		try {
			Properties p = new Properties();
			FileInputStream inputStream = new FileInputStream(new File("src/csdn1/druid.properties"));
			p.load(inputStream);
			druid = DruidDataSourceFactory.createDataSource(p);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	public static Connection getDruidConnection() throws SQLException {
		Connection cn = druid.getConnection();
		return cn;
	}

	// dbcp
	private static DataSource dbcp = null;
	static {
		try {
			Properties p = new Properties();
			InputStream inputStream = ClassLoader.getSystemClassLoader().getResourceAsStream("dbcp.properties");
			p.load(inputStream);
			dbcp = BasicDataSourceFactory.createDataSource(p);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	public static Connection getDbcpConnection() throws SQLException {
		Connection cn = dbcp.getConnection();
		return cn;
	}

	// c3p0
	public static ComboPooledDataSource c3p0 = new ComboPooledDataSource("xmlName");

	public static Connection getC3p0Connection() throws SQLException {
		Connection cn = c3p0.getConnection();
		return cn;
	}
}

User对象

package csdn1;

// 一条记录对应一个对象，User必须是公共类
public class User {
	private String id;
	private String name;
	private String password;

	public User() {
	}

	public User(String id, String name, String password) {
		this.id = id;
		this.name = name;
		this.password = password;
	}

	public void setId(String id) {
		this.id = id;
	}

	public void setName(String name) {
		this.name = name;
	}

	public void setPassword(String password) {
		this.password = password;
	}

	@Override
	public String toString() {
		return "User [id=" + id + ", name=" + name + ", password=" + password + "]";
	}

}

dbcp.properties 和druid.properties一样

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql:///mydbs2
username=root
password=root

c3p0-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
	<!-- 自定义name以实现文件配置 -->
	<named-config name="xmlName">
		<!-- 获取连接的四个信息 -->
		<property name="driverClass">com.mysql.jdbc.Driver</property>
		<property name="jdbcUrl">jdbc:mysql://localhost/mydbs2</property>
		<property name="user">root</property>
		<property name="password">root</property>

		<!-- 数据库连接池的基本信息 
			申请连接数 
			初始连接数 
			维护的最小连接数 
			维护的最大连接数 
			维护的最大Statement数 
			每个连接可使用的最大Statement数 
		-->
		<property name="acquireIncrement">5</property>
		<property name="initialPoolSize">10</property>
		<property name="minPoolSize">5</property>
		<property name="maxPoolSize">100</property>
		<property name="maxStatements">50</property>
		<property name="maxStatementsPerConnection">2</property>
		
	</named-config>
</c3p0-config>