标签：JDBC java String System day17 out public conn name

一、JDBC

JDBC编写六步走：
    1、注册驱动，告诉java程序我们要链接什么数据库
        【mysql为案例】
            5.1.x驱动包中的驱动类路径：【com.mysql.jdbc.Driver】
            8.x.x驱动包中的驱动类路径：【com.mysql.cj.jdbc.Driver】
    2、创建与数据库的链接对象
    3、创建操作数据库对象
    4、操作数据库对象调用方法执行sql语句，操作数据库
    5、如果第4步是查询操作的话，需要进一步分析查询结果
    6、释放资源，关闭与数据库的链接

代码案例：

public class JDBCDemo1 {
    public static void main(String[] args) throws Exception {
        // 注册驱动，告诉java程序我们要链接什么数据库
        Class.forName("com.mysql.jdbc.Driver");

        // 创建与数据库的链接对象
        // public static Connection getConnection(String url,String user, String password)
        /**
         * url: 超链接
         *  jdbc:mysql://192.168.6.101:3306/bigdata?characterEncoding=UTF-8&useUnicode=True&useSSL=false
         * username: root
         * password: 123456
         */
        String url = "jdbc:mysql://192.168.233.101:3306/bigdata?characterEncoding=UTF-8&useUnicode=True&useSSL=false";
        String username = "root";
        String password = "123456";
        Connection conn = DriverManager.getConnection(url, username, password);
        System.out.println("成功获取与mysql数据库的链接对象：" + conn);

        // 创建操作数据库对象
        Statement state = conn.createStatement();

        // 操作数据库对象调用方法执行sql语句，操作数据库
        // SQL - 结构化查询语言 只要是结构化数据库，基本都可以使用sql语句【mysql是其中一种】
        // 增删改，其它的操作
        // 增加
//        int i = state.executeUpdate("insert into students values(1007,'李刚2',18,'男','文科一班')");
//        if(i==1){
//            System.out.println("插入数据成功！");
//        }else {
//            System.out.println("插入数据失败！");
//        }
        // 删除
//        state.executeUpdate("delete from students where id=1007");
        // 修改
//        state.executeUpdate("update students set name='江川' where id=1006");

        // DQL 查询
        ResultSet resultSet = state.executeQuery("select t1.location as location,count(1) as counts from (select location from jd_comment where productColor='墨玉青') t1 group by t1.location order by counts desc limit 10");

//        resultSet.next();
//        String location = resultSet.getString(1);
//        String counts = resultSet.getString(2);
//        System.out.println(location+": "+counts);

        while (resultSet.next()){
            //根据列索引获取元素，从左向右从1开始
//            String location = resultSet.getString(1);
//            String counts = resultSet.getString(2);

            // 根据列名获取
            String location = resultSet.getString("location");
            String counts = resultSet.getString("counts");

            System.out.println(location+": "+counts);
        }

        // 释放资源，关闭与数据库的链接
        state.close();
        conn.close();

    }
}

二、登录注册修改案例

用户类存储用户的用户名和密码

public class User {
    private String name;
    private String pwd;

    public User() {
    }

    public User(String name, String pwd) {
        this.name = name;
        this.pwd = pwd;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

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

MySQL配置文件

url=jdbc:mysql://192.168.6.101:3306/bigdata?characterEncoding=UTF-8&useUnicode=True&useSSL=false
username=root
password=123456

MySQL连接工具类【获取MySQL连接对象】

import java.io.BufferedReader;
import java.io.FileReader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.util.Properties;

public class MySQLTool {
    private static Properties prop;
    private static Connection conn;
    private MySQLTool(){}

    public static Connection getConnection(){
        try {
            //创建Properties对象
            prop = new Properties();
            prop.load(new BufferedReader(new FileReader("D:\\projects\\ideaprojects\\bigdata\\src\\com\\wll\\day17\\mysql.properties")));
            String url = prop.getProperty("url");
            String username = prop.getProperty("username");
            String password = prop.getProperty("password");

            // 注册驱动，告诉java程序我们要链接什么数据库
            Class.forName("com.mysql.jdbc.Driver");

            conn = DriverManager.getConnection(url, username, password);
        }catch (Exception e){
            e.printStackTrace();
        }

        return conn;
    }
}

测试类

import com.wll.day17.entity.User;
import com.wll.day17.utils.MySQLTool;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Scanner;

public class IODemo1 {
    public static void init() {
        Scanner sc = new Scanner(System.in);
        System.out.println("========欢迎光临^_^========");
        System.out.println("----------------------------------");
        System.out.print("选择您要做的操作：1：登录，2：注册，3：修改密码：");
        int i = sc.nextInt();
        switch (i) {
            case 1:
                login();
                break;
            case 2:
                register();
                break;
            case 3:
                update();

        }
    }

    public static void update(){
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入用户名：");
        String name = sc.nextLine();
        if(!isUserExistWithName(name)){
            System.out.println("用户不存在，请注册");
            return;
        }
        System.out.println("请输入旧密码");
        String oldPassword = sc.nextLine();
        User user = getUserWithNameAndPassword(name,oldPassword);
        if (user!=null){
            System.out.println("请输入新密码：");
            String newPassword = sc.nextLine();
            updateUser(name,newPassword);
        }else {
            System.out.println("输入的密码不对！！");
        }

    }

    public static void updateUser(String name,String newPassword){

        Connection conn = null;
        Statement state = null;


        try {
            conn = MySQLTool.getConnection();
            state = conn.createStatement();

            int i = state.executeUpdate("update users set password ='" + newPassword + "' where name='" + name + "'");
            if (i==1) {
                System.out.println("密码修改成功！！");
            }else{
                System.out.println("密码修改失败！！");
            }
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            if (state != null) {
                try {
                    state.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (conn != null) {
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }


    }

    public static void register(){
        Scanner sc = new Scanner(System.in);
        System.out.print("请输入用户名：");
        String name = sc.nextLine();
        if (isUserExistWithName(name)){
            System.out.println("用户已存在");
            return;
        }
        System.out.print("请输入密码：");
        String password = sc.nextLine();

        saveUser(name,password);



    }

    public static void saveUser(String name,String pwd){

        Connection conn = null;
        Statement statement = null;

        try {
            conn = MySQLTool.getConnection();
            statement = conn.createStatement();

            int id = 0;
            ResultSet resultSet = statement.executeQuery("select max(id)  from users");
            while (resultSet.next()) {
                if(resultSet.getString(1)!=null){
                    id = Integer.parseInt(resultSet.getString(1)) + 1;
                }
                else {
                    id=1;
                }
            }
            String sql = "insert into users values(" + id + ",'" + name + "','" + pwd + "')";
            int i = statement.executeUpdate(sql);
            if (i == 1) {
                System.out.println("用户保存成功！！");
            } else {
                System.out.println("用户保存失败！！");
            }

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (statement != null) {
                try {
                    statement.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }

            if (conn != null) {
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }


    }

    public static void login() {
        Scanner sc = new Scanner(System.in);
        System.out.println("------------------>正在进行登录操作");
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.print("请输入用户名：");
        String name = sc.nextLine();
        if (!isUserExistWithName(name)) {
            System.out.println("用户不存在，请注册用户");
            return;
        }

        System.out.print("请输入密码：");
        String password = sc.nextLine();
        User user = getUserWithNameAndPassword(name, password);
        if (user!=null){
            System.out.println("登录成功");
        }else {
            System.out.println("您输入的密码不对");
        }


    }

    public static User getUserWithNameAndPassword(String name, String password) {
        Connection conn = null;
        Statement state = null;
        User user = null;

        try {
            conn = MySQLTool.getConnection();
            state = conn.createStatement();
            ResultSet resultSet = state.executeQuery("select name,password from users where name='" + name + "' and password='" + password + "'");
            while (resultSet.next()) {
                String userName = resultSet.getNString(1);
                String pwd = resultSet.getNString(2);
                user=new User(userName,pwd);
            }
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            if (state != null) {
                try {
                    state.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (conn != null) {
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
        return user;


    }



    public static Boolean isUserExistWithName(String name) {
        Connection conn = null;
        Statement state = null;
        boolean flag = false;

        try {
            conn = MySQLTool.getConnection();
            state = conn.createStatement();
            ResultSet resultSet = state.executeQuery("select name from users where name='" + name + "'");
            while (resultSet.next()) {
                flag = true;
            }
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            if (state != null) {
                try {
                    state.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (conn != null) {
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
        return flag;
    }

    public static void main(String[] args) {
        init();
    }
}

标签：JDBC,java,String,System,day17,out,public,conn,name
From： https://www.cnblogs.com/w-ll/p/18475485

java_day17_JDBC、登录注册修改案例

一、JDBC

二、登录注册修改案例

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