JDBC 学习笔记

学习参考视频:
[1] JDBC从入门到精通视频教程-JDBC实战精讲
[2] 尚硅谷JDBC核心技术视频教程(康师傅带你一站式搞定jdbc)

代码总结:
testConnection1()方法介绍了数据库连接的6个步骤:

1.注册JDBC驱动,告诉Java程序将要连接什么数据库;
2.Java程序连接数据库;
3.由连接对象创建操作SQL的对象;
4.执行SQL语句;
5.获取结果集;
6.JVM进程与数据库进程的通信是重量级的,因此需关闭资源。

后续方法都对上述步骤作了不同的优化,在方法上有说明。.

代码如下:

package com.bjpowernode;

import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

/**
 * @author: sjmp1573
 * @date: 2022/6/22 17:19
 * @description:
 */

public class JDBC01 {


    /**
     * 1.注册JDBC驱动,告诉Java程序将要连接什么数据库;
     * 2.Java程序连接数据库;
     * 3.由连接对象创建操作SQL的对象;
     * 4.执行SQL语句;
     * 5.获取结果集;
     * 6.JVM进程与数据库进程的通信是重量级的,因此需关闭资源。
     */
    @Test
    public void jdbcTest01() {
        Connection connection = null;
        Statement statement = null;
        try {
            Driver driver = new com.mysql.jdbc.Driver();
            DriverManager.registerDriver(driver);

            connection = DriverManager.getConnection("jdbc:mysql://ip:port/database", "xxx", "xxx");

            statement = connection.createStatement();
            String sql = "INSERT INTO `t_student`(`name`,`gender`) VALUE('小绿',1),('小黄',0);";
            // 返回值 i 表示:i行受到影响
            int i = statement.executeUpdate(sql);
            System.out.println(i);
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            if (statement != null) {
                try {
                    statement.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }


    /**
     * 优化 JDBC 驱动的注册过程:
     * 由于 com.mysql.jdbc 包中的 Driver 类已经的静态代码块中包含了驱动的注册过程;
     * 所以只需要通过反射加载该 Driver 类,即可完成驱动的注册;
     */
    @Test
    public void jdbcTest02() {
        Connection connection = null;
        Statement statement = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            connection = DriverManager.getConnection("jdbc:mysql://ip:port/database", "xxx", "xxx");

            statement = connection.createStatement();
            String sql = "DELETE FROM `t_student` WHERE `name` = '小黄';";
            int i = statement.executeUpdate(sql);
            System.out.println(i);
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {

            e.printStackTrace();

        } finally {
            if (statement != null) {
                try {
                    statement.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }


    /**
     * 将数据库的访问信息抽取到配置文件
     */
    @Test
    public void jdbcTest03() {

        InputStream inputStream = getClass().getClassLoader().getResourceAsStream("jdbc.properties");
        Properties properties = new Properties();
        try {
            properties.load(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }

        String driverClass = properties.getProperty("driverClass");
        String url = properties.getProperty("url");
        String user = properties.getProperty("user");
        String password = properties.getProperty("password");

        Connection connection = null;
        Statement statement = null;
        try {
            Class.forName(driverClass);
            connection = DriverManager.getConnection(url, user, password);

            statement = connection.createStatement();
            String sql = "INSERT INTO `t_student`(`name`,`gender`) VALUE('小绿',1),('小黄',0);";
            // 返回值 i 表示:i行受到影响
            int i = statement.executeUpdate(sql);
            System.out.println(i);
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } finally {
            if (statement != null) {
                try {
                    statement.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    /**
     * 使用 ResultSet 获取结果集,使用 statement.executeQuery() 执行查询操作。
     */
    @Test
    public void jdbcTest04() {
        InputStream inputStream = getClass().getClassLoader().getResourceAsStream("jdbc.properties");
        Properties properties = new Properties();
        try {
            properties.load(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }

        String driverClass = properties.getProperty("driverClass");
        String url = properties.getProperty("url");
        String user = properties.getProperty("user");
        String password = properties.getProperty("password");

        Connection connection = null;
        Statement statement = null;
        ResultSet resultSet = null;
        try {
            Class.forName(driverClass);
            connection = DriverManager.getConnection(url, user, password);

            statement = connection.createStatement();
            String sql = "SELECT * FROM `t_student`;";
            // 返回值 i 表示:i行受到影响,注意:由于是查询
            resultSet = statement.executeQuery(sql);
            while (resultSet.next()) {
                String name = resultSet.getString("name");
                String gender = resultSet.getInt("gender") == 0 ? "女" : "男";
                System.out.format("姓名:%s,性别:%s", name, gender);
                System.out.println();
            }

        } catch (SQLException | ClassNotFoundException e) {
            e.printStackTrace();
        } finally {
            if (statement != null) {
                try {
                    statement.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (resultSet!=null){
                try {
                    resultSet.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    /**
     * SQL 注入是利用某些系统没有对用户输入的数据进行充分的检查,而在用户输入数据中注入
     * 非法的SQL语句段或命令(如:
     * String sql = "select * from t_user where loginName = '" + loginName + "'and loginPwd='" + loginPwd +"'";
     * loginName = fdsa
     * loginPwd = fdsa' or '1'='1;
     * select * from t_user where loginName = 'fdsa' and loginPwd='fdsa' or '1'='1';
     * 由此引起的安全问题称为SQL注入;
     * 解决方案:PreparedStatement 提供的预编译功能,使用 ? 作为占位符,同时提高了语句查询的效率。
     */
    @Test
    public void jdbcTest05() {
        InputStream inputStream = getClass().getClassLoader().getResourceAsStream("jdbc.properties");
        Properties properties = new Properties();
        try {
            properties.load(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }

        String driverClass = properties.getProperty("driverClass");
        String url = properties.getProperty("url");
        String user = properties.getProperty("user");
        String password = properties.getProperty("password");

        Connection connection = null;
        PreparedStatement statement = null;
        ResultSet resultSet = null;
        try {
            Class.forName(driverClass);
            connection = DriverManager.getConnection(url, user, password);

            String sql = "SELECT * FROM `t_user` where loginName = ? and loginPwd = ?;";
            statement = connection.prepareStatement(sql);
            statement.setString(1, "sjmp");
            statement.setString(2, "666666");
            // 返回值 i 表示:i行受到影响,注意:由于是查询
            resultSet = statement.executeQuery(sql);
            while (resultSet.next()) {
                String name = resultSet.getString("name");
                String gender = resultSet.getInt("gender") == 0 ? "女" : "男";
                System.out.format("姓名:%s,性别:%s", name, gender);
                System.out.println();
            }

        } catch (SQLException | ClassNotFoundException e) {
            e.printStackTrace();
        } finally {
            if (statement != null) {
                try {
                    statement.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (resultSet != null){
                try {
                    resultSet.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    /**
     * 设置事务
     * 1.取消事务自动提交功能 connection.setAutoCommit(false);
     * 2.没有出现异常,全部提交 connection.commit();
     * 3.出现异常,开始回滚 connection.rollback();
     */
    @Test
    public void jdbcTest06() {
        InputStream inputStream = getClass().getClassLoader().getResourceAsStream("jdbc.properties");
        Properties properties = new Properties();
        try {
            properties.load(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }

        String driverClass = properties.getProperty("driverClass");
        String url = properties.getProperty("url");
        String user = properties.getProperty("user");
        String password = properties.getProperty("password");

        Connection connection = null;
        PreparedStatement statement = null;
        try {
            Class.forName(driverClass);

            connection = DriverManager.getConnection(url, user, password);

            // 1.取消事务自动提交功能
            connection.setAutoCommit(false);
//           事务逻辑代码,几个sql语句要么都执行,要么都不执行...
            //2.没有出现异常,全部提交
            connection.commit();
        } catch (SQLException | ClassNotFoundException e) {
            //3.出现异常,开始回滚
            try {
                connection.rollback();
            } catch (SQLException ex) {
                ex.printStackTrace();
            }
            e.printStackTrace();
        } finally {
            if (statement != null) {
                try {
                    statement.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    
   /**
     * 使用数据库连接池获取数据库连接 druid
     */
    @Test
    public void jdbcTest07() {

        InputStream inputStream = getClass().getClassLoader().getResourceAsStream("jdbc.properties");
        Properties properties = new Properties();
        DataSource dataSource = null;
        Connection connection = null;
        PreparedStatement statement = null;
        ResultSet resultSet = null;
        try {
            properties.load(inputStream);
            dataSource = DruidDataSourceFactory.createDataSource(properties);
            connection = dataSource.getConnection();
            String sql = "SELECT * FROM `t_student` ;";
            statement = connection.prepareStatement(sql);
            resultSet = statement.executeQuery();
            while (resultSet.next()){
                String name = resultSet.getString("name");
                String gender = resultSet.getInt("gender") == 0 ? "女" : "男";
                System.out.format("姓名:%s,性别:%s", name, gender);
                System.out.println();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            if (statement != null) {
                try {
                    statement.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (resultSet!=null){
                try {
                    resultSet.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

你可能感兴趣的:(学习笔记,Java基础,学习,java,sql)