一、Druid连接池在程序初始化时，预先创建指定数量的数据库连接对象存储在池中。

当需要连接数据库时，从连接池中取出现有连接；

使用完毕后, 也不会进行关闭，而是放回池中，实现复用，节省资源。

1.1 Druid连接池使用步骤创建 database.properties 配置文件。

引入druid-1.1.5.jar文件。

1.1.1database.properties 配置文件#连接设置

driverClassName=com.mysql.jdbc.Driver

url=jdbc:mysql://localhost:3306/companydb?useUnicode=true&characterEncoding=utf

username=root

password=root

#

initialSize=10

#最大连接数量

maxActive=50

#

minldle=5

# 放回池中

connection.close();//调用的是DruidPooledConnection实现类里的close()方法

}

}

}

二、Apache的DbUtils使用Commons DbUtils是Apache组织提供的一个对JDBC逬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，不会影响程序的性能。

2.1 DbUtils 简介DbUtils是Java编程中数据库操作实用小工具，小巧、简单、实用对于数据表的查询操作，可以把结果转换为List、Array、Set等集合。便于操作。

对于数据表的DML操作，也变得很简单(只需要写SQL语句)。

2.1.1DbUtils主要包含ResultSetHandler接口：转换类型接口BeanHandler类：实现类，把一条记录转换成对象 (查询单个)

BeanListHandler类：实现类，把多条记录转换成List集合。 (查询所有)

ScalarHandler类：实现类，适合获取一行一列的数据。

QueryRunner: 执行sql语句的类增、删、改：update();

查询：query();

2.2DbUtils的使用步骤导入jar包mysql连接驱动jar包 mysql-connector-java-5.1.28-bin.jar

druid-1.1.5.jar

database.properties配置文件

commons-dbutils-1.6,jar

2.2.1 DbUtils 工具类package com.ziming.chapter1_JDBC.demo05_jdbcfinal.utils;

import com.alibaba.druid.pool.DruidDataSource;

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;

import java.io.IOException;

import java.io.InputStream;

import java.sql.Connection;

import java.sql.SQLException;

import java.util.Properties;

public class DbUtils {

//声明连接池对象

private static DruidDataSource ds;

static {

Properties properties = new Properties();

InputStream is = DbUtils.class.getResourceAsStream("/database.properties");

try {

properties.load(is);

//创建连接池

ds = (DruidDataSource)DruidDataSourceFactory.createDataSource(properties);

} catch (IOException e) {

e.printStackTrace();

} catch (Exception e) {

e.printStackTrace();

}

}

public static Connection getConnection(){

try {

return ds.getConnection();//通过连接池获得 连接对象

} catch (SQLException e) {

e.printStackTrace();

}

return null;

}

public static DataSource getDataSource(){ //获得 DataSource 连接池对象

return ds;

}

}

2.2.2 UserDaoImpl数据访问对象package com.ziming.chapter1_JDBC.demo05_jdbcfinal.entity;

public class User {

private int id;

private String username;

private String password;

private String phone;

public User() {}

public User(int id, String username, String password, String phone) {

this.id = id;

this.username = username;

this.password = password;

this.phone = phone;

}

@Override

public String toString() {

return "user{" +

"id=" + id +

", username='" + username + '\'' +

", password='" + password + '\'' +

", phone='" + phone + '\'' +

'}';

}

public int getId() { return id; }

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

public String getUsername() { return username; }

public void setUsername(String username) { this.username = username; }

public String getPassword() { return password; }

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

public String getPhone() { return phone; }

public void setPhone(String phone) { this.phone = phone; }

}

package com.ziming.chapter1_JDBC.demo05_jdbcfinal.dao;

import com.ziming.chapter1_JDBC.demo05_jdbcfinal.entity.User;

import java.util.List;

public interface UserDao {

public int insert(User user);

public int update(User user);

public int delete(int id);

public User select(int id);

public List selectAll();

//查看目前多少条记录(用户数量)

public long selectUserNums();

}

package com.ziming.chapter1_JDBC.demo05_jdbcfinal.dao.impl;

import com.ziming.chapter1_JDBC.demo05_jdbcfinal.dao.UserDao;

import com.ziming.chapter1_JDBC.demo05_jdbcfinal.entity.User;

import com.ziming.chapter1_JDBC.demo05_jdbcfinal.utils.DbUtils;

import org.apache.commons.dbutils.QueryRunner;

import org.apache.commons.dbutils.handlers.BeanHandler;

import org.apache.commons.dbutils.handlers.BeanListHandler;

import org.apache.commons.dbutils.handlers.ScalarHandler;

import javax.swing.*;

import java.sql.SQLException;

import java.util.List;

public class UserDaoImpl implements UserDao {

private QueryRunner queryRunner = new QueryRunner(DbUtils.getDataSource());

@Override

public int insert(User user) {

String sql = "insert into user(username,password,phone) values (?,?,?);";

try {

return queryRunner.update(sql,user.getUsername(),user.getPassword(),user.getPhone());

} catch (SQLException e) {

e.printStackTrace();

}

return 0;

}

@Override

public int update(User user) {

String sql = "update user set username=?,password=?,phone=? where id=?;";

try {

return queryRunner.update(sql,user.getUsername(),user.getPassword(),user.getPhone(),user.getId());

} catch (SQLException e) {

e.printStackTrace();

}

return 0;

}

@Override

public int delete(int id) {

String sql = "delete from user where id=?;";

try {

return queryRunner.update(sql,id);

} catch (SQLException e) {

e.printStackTrace();

}

return 0;

}

@Override

public User select(int id) {

String sql = "select * from user where id=?;";

try {

User user = queryRunner.query(sql, new BeanHandler(User.class), id);

return user;

} catch (SQLException e) {

e.printStackTrace();

}

return null;

}

@Override

public List selectAll() {

String sql = "select * from user;";

try {

List list = queryRunner.query(sql, new BeanListHandler(User.class));

return list;

} catch (SQLException e) {

e.printStackTrace();

}

return null;

}

@Override

public long selectUserNums() {

String sql = "select count(*) from user";

try {

long count = queryRunner.query(sql, new ScalarHandler<>());

return count;

} catch (SQLException e) {

e.printStackTrace();

}

return 0;

}

}

package com.ziming.chapter1_JDBC.demo05_jdbcfinal.test;

import com.ziming.chapter1_JDBC.demo05_jdbcfinal.dao.UserDao;

import com.ziming.chapter1_JDBC.demo05_jdbcfinal.dao.impl.UserDaoImpl;

import com.ziming.chapter1_JDBC.demo05_jdbcfinal.entity.User;

import java.util.List;

public class TestDbUtils {

public static void main(String[] args) {

UserDao userDao = new UserDaoImpl();

//User user = new User(3,"xiaoli","123456","1234569874");

//int result = userDao.insert(user); //新增

//User user = new User(3,"xiaoli","123","1234569874");

//int result = userDao.update(user); //修改

//int result = userDao.delete(3);//删除

//System.out.println(result);

//查单个

// User user = userDao.select(1);

// System.out.println(user);

//查所有

//List list = userDao.selectAll();

//list.forEach(System.out::println);

long count = userDao.selectUserNums();

System.out.println("一共有："+count);

}

}