idea连接数据库进行查找

首先需要打印出来，所以我们先创建一个类，用来对应数据库中的值并且输出。

public class User {
    private Integer id;
    private String name;
    private int age;
    private int teacherId;

    public int getTeacherId() {
        return teacherId;
    }

    public void setTeacherId(int teacherId) {
        this.teacherId = teacherId;
    }
       public User(Integer id, String name, int age,int teacherId) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.teacherId=teacherId;
    }


    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", teacherId=" + teacherId +
                '}';
    }

    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 int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
调用类中需要有七个步骤

1连接数据库

2.编写？sql

3.预编译

4.填充占位符

5.执行

6判断是否有值，然后打印

7.关闭

package cn.kgc.conn.Hello;
import cn.kgc.conn.Hello.User;
import cn.kgc.conn.Hello.jdbcUtil;


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

/**
 * Created by helloworld on 2020/6/24.
 * 根据id查询一个数据
 */
public class select {

    public static void main(String[] args){
        Connection connection=null;
        PreparedStatement pstm=null;
        ResultSet rs=null;

        //1连接数据库
        try {
            connection = jdbcUtil.getConnection();

            //2.编写？sql

            String sql ="SELECT * FROM student where Id =?";

            //3.预编译

            pstm = connection.prepareStatement(sql);


            //4.填充占位符
            pstm.setObject(1,"2");

            //5.执行
            rs = pstm.executeQuery();

            //6判断是否有值，然后打印
            if(rs.next()){
                /*int id = rs.getInt(1);
                String name = rs.getString(2);
                int age = rs.getInt(3);
*/
                int id = rs.getInt("id");
                String name = rs.getString("name");
                int age = rs.getInt("age");
                int teacherId =rs.getInt("teacherId");

               User user = new User(id,name,age,teacherId);
                System.out.println(user.toString());

                //  System.out.println("id:"+id+",name:"+name+",age"+age);


            }




        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            //7.关闭

            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }


            try {
                pstm.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }


            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }


        }
        }

    }