Java自学-MySQL(8)

1、数据库的三大范式

2、数据库驱动和JDBC

3、第一个JDBC程序

package lesson01;

/**
 * Author: Gu Jiakai
 * Date: 2021/8/27 21:18
 * FileName: JdbcDemo01
 * Description:
 */

import java.sql.*;

public class JdbcDemo01 {
    public static void main(String[] args) throws ClassNotFoundException, SQLException {
        //1.加载驱动
        Class.forName("com.mysql.jdbc.Driver"); //固定写法

        //2.用户信息和url
        String url = "jdbc:mysql://localhost:3306/jdbcstudy?useUnicode=true&characterEncoding=utf8&&useSSL=false";
        String name = "root";
        String password = "123456";

        //3.连接成功，返回数据库对象，connection代表数据库
        Connection connection = DriverManager.getConnection(url, name, password);

        //4.执行SQL的对象statement
        Statement statement = connection.createStatement();

        //5.执行SQL的对象，去执行SQL 可能存在结果，查看返回结果
        String sql = "SELECT * FROM users";
        ResultSet resultSet = statement.executeQuery(sql);
        while (resultSet.next()) {
            System.out.println("id=" + resultSet.getObject("id"));
            System.out.println("name=" + resultSet.getObject("NAME"));
            System.out.println("pwd=" + resultSet.getObject("PASSWORD"));
            System.out.println("email=" + resultSet.getObject("email"));
            System.out.println("birthday=" + resultSet.getObject("birthday"));
            System.out.println("--------");
        }

        //6.释放连接
        resultSet.close();
        statement.close();
        connection.close();
    }
}

4、JDBC中对象解释

5、Statement对象详解

JdbcUtils.java

package lesson02.utils;

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

/**
 * Author: Gu Jiakai
 * Date: 2021/8/28 15:51
 * FileName: JdbcUtils
 * Description:
 */
public class JdbcUtils {
    private static String driver = null;
    private static String url = null;
    private static String username = null;
    private static String password = null;

    static {
        try {
            InputStream in = JdbcUtils.class.getClassLoader().getResourceAsStream("db.properties");
            Properties properties = new Properties();
            properties.load(in);

            driver = properties.getProperty("driver");
            url = properties.getProperty("url");
            username = properties.getProperty("username");
            password = properties.getProperty("password");

            //1、驱动只用加载一次
            Class.forName(driver);

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    //获取连接
    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(url, username, password);
    }

    //释放连接资源
    public static void release(Connection conn, Statement st, ResultSet rs){
        if(rs!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(st!=null){
            try {
                st.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(conn!=null){
            try {
                conn.close();
            } catch (SQLException e) {

            }
        }
    }
}

TestInsert.java

package lesson02;

import lesson02.utils.JdbcUtils;

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

/**
 * Author: Gu Jiakai
 * Date: 2021/8/28 16:32
 * FileName: TestInsert
 * Description:
 */
public class TestInsert {
    public static void main(String[] args) {
        Connection conn=null;
        Statement st=null;
        ResultSet rs=null;

        try {
            conn= JdbcUtils.getConnection();//获取数据库连接
            st=conn.createStatement();//获得SQL的执行对象
            String sql="insert \n" +
                    "into users\n" +
                    "values(4,‘caiwei‘,‘123456‘,‘caiwei@qq.com‘,‘2001-01-01‘)";
            int i=st.executeUpdate(sql);
            if(i>0){
                System.out.println("插入成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            JdbcUtils.release(conn,st,rs);
        }
    }
}

TestDelete.java

package lesson02;

import lesson02.utils.JdbcUtils;

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

/**
 * Author: Gu Jiakai
 * Date: 2021/8/28 16:47
 * FileName: TestDelete
 * Description:
 */
public class TestDelete {
    public static void main(String[] args) {
        Connection conn=null;
        Statement st=null;
        ResultSet rs=null;

        try {
            conn= JdbcUtils.getConnection();//获取数据库连接
            st=conn.createStatement();//获得SQL的执行对象
            String sql="delete\n" +
                    "from users\n" +
                    "where id=4";
            int i=st.executeUpdate(sql);
            if(i>0){
                System.out.println("删除成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            JdbcUtils.release(conn,st,rs);
        }
    }
}

TestUpdate.java

package lesson02;

import lesson02.utils.JdbcUtils;

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

/**
 * Author: Gu Jiakai
 * Date: 2021/8/28 16:50
 * FileName: TestUpdate
 * Description:
 */
public class TestUpdate {
    public static void main(String[] args) {
        Connection conn=null;
        Statement st=null;
        ResultSet rs=null;

        try {
            conn= JdbcUtils.getConnection();//获取数据库连接
            st=conn.createStatement();//获得SQL的执行对象
            String sql="update users\n" +
                    "set `NAME`=‘caiwei‘,email=‘caiwei@qq.com‘\n" +
                    "where id=1";
            int i=st.executeUpdate(sql);
            if(i>0){
                System.out.println("更新成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            JdbcUtils.release(conn,st,rs);
        }
    }
}

TestSelect.java

package lesson02;

import lesson02.utils.JdbcUtils;

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

/**
 * Author: Gu Jiakai
 * Date: 2021/8/28 16:56
 * FileName: TestSelect
 * Description:
 */
public class TestSelect {
    public static void main(String[] args) {
        Connection conn=null;
        Statement st=null;
        ResultSet rs=null;

        try {
            conn = JdbcUtils.getConnection();
            st=conn.createStatement();

            String sql="select * from users where id=1";

            rs = st.executeQuery(sql);//查询完毕会返回一个结果集
            while(rs.next()){
                System.out.println(rs.getString("NAME"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
        }
    }
}

Java自学-MySQL(8)