java连接数据库实现增删改查功能

package com.atguigu.api.preparedstatement;

import org.junit.Test;

import java.sql.*;
import java.util.Scanner;

public class PreparedStatement_CRUD_Test {

    //TODO java实现数据库添加功能
    @Test
    public void InsertTest() throws ClassNotFoundException, SQLException {
        Class.forName("com.mysql.cj.jdbc.Driver");

        Connection connection = DriverManager.getConnection("jdbc:mysql://127.0.0.1/atguigu", "root", "123456");

        String insertSql = "insert into t_user(account,password,nickname)values(?,?,?)";
        PreparedStatement preparedStatement = connection.prepareStatement(insertSql);

        preparedStatement.setObject(1,"lisi");
        preparedStatement.setObject(2,"lisi");
        preparedStatement.setObject(3,"李四");

        int i = preparedStatement.executeUpdate();
        if (i>0){
            System.out.println("数据插入成功！");
        }else{
            System.out.println("数据插入失败！");
        }
        preparedStatement.close();
        connection.close();
    }

    //TODO java实现数据库修改功能
    @Test
    public void UpdateTest() throws ClassNotFoundException, SQLException {
        Class.forName("com.mysql.cj.jdbc.Driver");
        Connection connection = DriverManager.getConnection("jdbc:mysql:///atguigu", "root", "123456");
        String updateSql = "update t_user set nickname = ? where id = ?";
        PreparedStatement preparedStatement = connection.prepareStatement(updateSql);
        preparedStatement.setObject(1,"王五");
        preparedStatement.setObject(2,3);
        int i = preparedStatement.executeUpdate();
        if (i>=1){
            System.out.println("数据修改成功！");
        }else {
            System.out.println("数据修改失败！");
        }
    }

    //TODO java实现数据库删除功能
    @Test
    public void DeleteTest() throws ClassNotFoundException, SQLException {
        Class.forName("com.mysql.cj.jdbc.Driver");
        Connection connection = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/atguigu", "root", "123456");
        String deleteSql = "delete from t_user where id = ?";
        PreparedStatement preparedStatement = connection.prepareStatement(deleteSql);
        preparedStatement.setObject(1,5);
        int i = preparedStatement.executeUpdate();
        if (i>=1){
            System.out.println("数据删除成功！");
        }else {
            System.out.println("数据删除失败！");
        }
        preparedStatement.close();
        connection.close();
    }

    //TODO java实现数据库查询功能
    @Test
    public void SelectTest() throws ClassNotFoundException, SQLException {
        Class.forName("com.mysql.cj.jdbc.Driver");
        Connection connection = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/atguigu", "root", "123456");
        String selectSql = "select * from t_user";
        String selectSql_id = "select * from t_user where id = ?";
        PreparedStatement preparedStatement = connection.prepareStatement(selectSql);
        PreparedStatement preparedStatement_id = connection.prepareStatement(selectSql_id);
        preparedStatement_id.setObject(1,1);

        ResultSet resultSet = preparedStatement.executeQuery();
        ResultSet resultSet_id = preparedStatement_id.executeQuery();

        while (resultSet.next()){
            System.out.print(resultSet.getString("account")+"----");
            System.out.print(resultSet.getString("password")+"----");
            System.out.println(resultSet.getString("nickname"));
        }

        System.out.println();
        while (resultSet_id.next()){
            System.out.print(resultSet_id.getString("account")+"----");
            System.out.print(resultSet_id.getString("password")+"----");
            System.out.println(resultSet_id.getString("nickname"));
        }
        preparedStatement.close();
        preparedStatement_id.close();
        connection.close();
    }
}