JDBC

入门程序，执行修改操作

import org.junit.jupiter.api.Test;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;

public class JDBC {
    @Test
    public void testUpdate() throws Exception {
        //1.连接驱动
        Class.forName("com.mysql.cj.jdbc.Driver");
        //2.连接数据库
        String url = "jdbc:mysql://localhost:3306/web01";
        String username = "root";
        String password = "1110";
        Connection connection = DriverManager.getConnection(url,username,password);
        //3.获取SQL语句执行对象
        Statement statement = connection.createStatement();
        //4.执行SQL
        int i = statement.executeUpdate("update user set age=25 where id=1");
        System.out.println(i);//执行语句后受影响的数据条数
        //5.释放资源
        statement.close();
        connection.close();
    }
}

执行DQL语句

//实体类
package org.example.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    private Integer id;
    private String username;
    private String password;
    private String name;
    private Integer age;
}

import org.example.pojo.User;
import org.junit.jupiter.api.Test;

import java.sql.*;

public class JDBC {
    @Test
    public void testSelect() throws Exception {
        ResultSet rs = null;
        //1.连接驱动
        Class.forName("com.mysql.cj.jdbc.Driver");
        //2.连接数据库
        String url = "jdbc:mysql://localhost:3306/web01";
        String username = "root";
        String password = "1110";
        Connection connection = DriverManager.getConnection(url,username,password);
        //3.执行SQL
        String sql = "select id,username,password,name,age from user where username = ? and password = ?";
        PreparedStatement stmt = connection.prepareStatement(sql);

        stmt.setString(1,"daqiao");
        stmt.setString(2,"123456");

        rs = stmt.executeQuery();

        //4.处理结果集
        while (rs.next()){
            User user = new User(
                    rs.getInt("id"),
                    rs.getString("username"),
                    rs.getString("password"),
                    rs.getString("name"),
                    rs.getInt("age")
            );
            System.out.println(user.toString());
        }
        //5.释放资源
        stmt.close();
        connection.close();
    }
}