Druid 德鲁伊连接池

public  void druidTest() throws Exception {
        //创建一个Properties 对象 读取配置文件
        Properties properties = new Properties();
        properties.load(new FileInputStream("src\\druid.properties"));
        // 创建一个指定参数的数据库连接池, Druid 连接池
        DataSource dataSource = DruidDataSourceFactory.createDataSource(properties);
        //建立连接
        Connection connection = dataSource.getConnection();
        System.out.println("连接成功");
        connection.close();
    }

配置文件

#key=value
driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/jdbcstudy?rewriteBatchedStatements=true&useUnicode=true&characterEncoding=utf8&useSSL=false&serverTimezone=UTC
username=root
password=root
#initial connection Size
initialSize=10
#min idle connecton size
minIdle=5
#max active connection size
maxActive=20
#max wait time (5000 mil seconds)  最大等待时间(等待队列)
maxWait=5000

Druid工具类

package com.JDBC_Utils;

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class JDBCUtilsByDruid {
    /**
     * 基于 druid 数据库连接池的工具类
     */
    private static DataSource ds;

    static {
        try {
            //创建一个Properties 对象 读取配置文件
            Properties properties = new Properties();
            properties.load(new FileInputStream("src\\druid.properties"));
            // 创建一个指定参数的数据库连接池, Druid 连接池
            ds = DruidDataSourceFactory.createDataSource(properties);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

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

    public static void close(ResultSet resultSet, Statement statement, Connection connection) {
        try {
            //关闭连接： 在数据库连接池技术中，close 不是真的断掉连接
            //而是把使用的 Connection 对象放回连接池
            if (resultSet != null) {
                resultSet.close();
            }
            if (statement != null) {
                statement.close();
            }
            if (connection != null) {
                connection.close();
            }
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
    }
}

对Druid工具类测试

package com.JDBC_Utils;

import org.junit.jupiter.api.Test;

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

public class JDBCUtilsByDruidTest {

    @Test
    public void select() {
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        String sql = "select * from news where id=?";
        ResultSet resultSet = null;
        try {
            //建立连接
            connection = JDBCUtilsByDruid.getConnection();
            //创建一个 PreparedStatement对象，用于将参数化的SQL语句发送到数据库。
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setObject(1, 10);
            //执行sql语句，返回一个结果集
            resultSet = preparedStatement.executeQuery();
            while (resultSet.next()) {
                System.out.println(resultSet.getObject("id"));
                System.out.println(resultSet.getObject("content"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JDBCUtilsByDruid.close(resultSet, preparedStatement, connection);
            System.out.println("执行完毕~");
        }
    }

    @Test
    public void Dml() {
        Connection connection = null;
        PreparedStatement preparedStatement = null;

        try {
            //建立连接
            connection = JDBCUtilsByDruid.getConnection();
            //插入语句
            String sql = "insert into news values (?,?)";
            //创建一个 PreparedStatement对象，用于将参数化的SQL语句发送到数据库
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setObject(1, 11);
            preparedStatement.setObject(2, 11);
            //执行sql语句
            int rows = preparedStatement.executeUpdate();
            System.out.println(rows > 0 ? "操作成功" : "操作失败");
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JDBCUtilsByDruid.close(null, preparedStatement, connection);
        }
    }
}

(土方法) ResultSet =封装=> Arraylist

//这里当我们关闭连接时，就无法再次获取 结果集的 内容，要想对关闭连接后的 结果集 进行操作 
//我们可以在获取结果集的时候 创建 一个表 的类(表中的每一列对应类的属性)，表中的每一条记录都是一个对象，
// 将每一次获得的记录封装到ArrayList集合中，就可以对获取的记录进行操作管理
   @Test
    public void selectToArrayList() {
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        //String sql = "select * from news where id=?";
        String sql = "select * from news ";
        ResultSet resultSet = null;
        ArrayList<News> list = new ArrayList<>();
        try {
            //建立连接
            connection = JDBCUtilsByDruid.getConnection();
            //创建一个 PreparedStatement对象，用于将参数化的SQL语句发送到数据库。
            preparedStatement = connection.prepareStatement(sql);
            //preparedStatement.setObject(1, 10);
            //执行sql语句，返回一个结果集
            // resultSet = preparedStatement.executeQuery();
            resultSet = preparedStatement.executeQuery(sql);

            while (resultSet.next()) {
                int id = resultSet.getInt("id");
                String name = resultSet.getString("name");
                String content = resultSet.getString("content");
            //把得到的 resultset 的记录，封装到 News 对象，放入到 list 集合
                list.add(new News(id, name, content));  //将每次获取的记录封装到 集合中
            }
            System.out.println(list);
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JDBCUtilsByDruid.close(resultSet, preparedStatement, connection);
            System.out.println("执行完毕~");
        }
    }

将数据库的 表 当作一个 类进行操作管理 （JavaBean） (此类要 公开 )

package com.JDBC_Utils;

public class News {

    //属性顺序要与数据库列名保持一致
    private Integer id;
    private String name;
    private String content;

    //一定要有无参构造器,反射需要
    public News() {
    }

    public News(Integer id, String name, String content) {
        this.id = id;
        this.name = name;
        this.content = content;
    }

    @Override
    public String toString() {
        return "\nNews\n{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", content=" + content +
                '}';
    }

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }
}