JDBC 基础操作

Class.forName(driverClass)

//加载 MySql 驱动
Class.forName("com.mysql.jdbc.Driver")

//加载 Oracle 驱动
Class.forName("oracle.jdbc.driver.OracleDriver")

// url ☞ jdbc:mysql://主机名称:mysql服务端口号/数据库名称?参数=值&参数=值
Connection connection = DriverManager.getConnection(url, username, password);

// 获取 MySQL 连接
// 如果JDBC程序与服务器端的字符集不一致，会导致乱码，那么可以通过参数指定服务器端的字符集
// jdbc:mysql://localhost:3306/mydatabase?useUnicode=true&characterEncoding=utf8
Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydatabase", "root", "root");

// 执行的 sql 语句
String sql = "insert into ···";

// 创建 Statement 对象
Statement statement = connection.createStatement();

// 采用倒序关闭
resultSet.close();
statement.close();
connection.close();

import java.sql.*;

/**
 * Created with IntelliJ IDEA.
 *
 * @author Demo_Null
 * @date 2020/7/9
 * @description JDBC 演示类
 */
public class JDBCTest {

    private static String url = "jdbc:mysql://47.103.4.*:3306/mydatabase";
    private static String username = "root";
    private static String password = "root";
    private static String drive = "com.mysql.jdbc.Driver";
    private static Connection connection = null;

    static {
        try {
            // 加载驱动程序
            Class.forName(drive);
            // 获得数据库连接
            connection = DriverManager.getConnection(url, username, password);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static void sql(String id) {
        try {
            // sql 语句
            String sql = "select * from dept where id = " + id;

            // 获取执行器
            Statement statement = connection.createStatement();

            // 执行 sql
            ResultSet resultSet = statement.executeQuery(sql);

            // 处理结果集
            while (resultSet.next()) {
                String dname = resultSet.getString("dname");
                System.out.println(dname);
            }

            // 释放资源
            resultSet.close();
            statement.close();
            connection.close();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }

    }

    public static void main(String[] args) {
        sql(" 1 ");
    }
}

import java.sql.*;

/**
 * Created with IntelliJ IDEA.
 *
 * @author Demo_Null
 * @date 2020/7/9
 * @description JDBC 演示类
 */
public class JDBCTest {

    private static String url = "jdbc:mysql://47.103.4.*:3306/mydatabase";
    private static String username = "root";
    private static String password = "root";
    private static String drive = "com.mysql.jdbc.Driver";
    private static Connection connection = null;

    static {
        try {
            // 加载驱动程序
            Class.forName(drive);
            // 获得数据库连接
            connection = DriverManager.getConnection(url, username, password);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static void sql(String id) {
        try {
            // sql 语句
            String sql = "select * from dept where id = ?";

            // 获取执行器
            PreparedStatement preparedStatement = connection.prepareStatement(sql);

            // 设置参数
            preparedStatement.setString(1, id);

            // 执行 sql
            ResultSet resultSet = preparedStatement.executeQuery();

            // 打印执行语句
            System.out.println(preparedStatement.toString());

            // 处理结果集
            while (resultSet.next()) {
                String dname = resultSet.getString("dname");
                System.out.println(dname);
            }

            // 释放资源
            resultSet.close();
            preparedStatement.close();
            connection.close();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }

    }

    public static void main(String[] args) {
        sql(" 1 or 1 = 1 ");
    }
}

driver = com.mysql.jdbc.Driver
url = jdbc:mysql://47.103.4.*:3306/mydatabase
user = work
password = mymima

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;
 
public class jdbc_utils {
    static String driver;
    static String url;
    static String user;
    static String password;
 
    static {
       /**  【需要获取配置文件路径是使用这种方式】
        *    // 加载本类字节码文件进内存，获取统一资源定位符(URL)
        *    URL url = jdbc_utils.class.getClassLoader().getResource("jdbc.properties");    
        *    // 获取 URL 路径
        *    String s = url.getParth();
        *    // 使用 File
        *    pro.load(new File(s));
        */
        
        // 加载字节码文件获取配置文件流
        InputStream is = jdbc_utils.class.getClassLoader().getResourceAsStream("jdbc.properties");
        
        try {
            // 创建 properties 集合
            Properties pro = new Properties();
            // 从文件中加载 key-value 对
            pro.load(is);
 
            // 获取属性并复制
            driver = pro.getProperty("driver");
            url = pro.getProperty("url");
            user = pro.getProperty("user");
            password = pro.getProperty("password");
 
            // 加载驱动
            Class.forName(driver);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
 
    // 获取数据库连接
    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(url,user,password);
    }
 
    // 释放资源
    // DML 释放两个资源
    public static void close(PreparedStatement preparedStatement, Connection connection) {
        if (preparedStatement != null) {
            try {
                preparedStatement.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
 
        if (connection != null) {
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
 
    // DQL 释放三个资源
    public static void close(ResultSet resultSet, PreparedStatement preparedStatement, Connection connection) {
        if (resultSet != null) {
            try {
                resultSet.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
 
        if (preparedStatement != null) {
            try {
                preparedStatement.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
 
        if (connection != null) {
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}