Java实现控制台登录(控制台输入的数据与数据库中的数据匹配) 注册

登录

说明:从控制台输入用户名和密码,然后从数据库中查询该用户是否存在,如果存在,
将数据信息保存在User类的对象中,返回该类的对象控制台输出欢迎登录,如果不存在,控制台输出登录失败

前提:已建好一张数据库表,如下图所示:

User类

package com.lanou3g.jdbc;

import java.sql.Date;

public class User {
// 对象中声明的属性名尽量和数据库中的字段相同
private int id;
private String name;
private String password;
private String email;
private Date birthday;
public User() {
super();
// TODO Auto-generated constructor stub
}
public User(int id, String name, String password, String email, Date birthday) {
super();
this.id = id;
this.name = name;
this.password = password;
this.email = email;
this.birthday = birthday;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
@Override
public String toString() {
return "User [id=" + id + ", name=" + name + ", password=" + password + ", email=" + email + ", birthday="
+ birthday + "]";
}
}

登录类

package com.lanou3g.jdbc;

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

public class Demo07 {
static {
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
throw new RuntimeException("驱动加载失败");
}
}
public static User getUser(String name1,String password1) {
User user = null;
try {
String url = "jdbc:mysql://localhost:3306/myjdbc";
Connection connection = DriverManager.getConnection(url,"root","123456");
Statement statement = connection.createStatement();
String sql = "select * from users where name = '"+name1+"' "
+ "and password = '"+password1+"'";
ResultSet resultSet = statement.executeQuery(sql);
if(resultSet.next()) {
user = new User();

4000
user.setId(resultSet.getInt("id"));
user.setName(resultSet.getString("name"));
user.setPassword(resultSet.getString("password"));
user.setEmail(resultSet.getString("email"));
user.setBirthday(resultSet.getDate("birthday"));
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return user;
}
}

测试登录类

package com.lanou3g.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Scanner;

public class Test {
public static void main(String[] args) {
System.out.println("请输入用户名");
Scanner scanner = new Scanner(System.in);
String name = scanner.nextLine();
System.out.println("请输入密码");
Scanner scanner2 = new Scanner(System.in);
String password = scanner.nextLine();
User user = Demo07.getUser(name, password);
if(user == null) {
System.out.println("登录失败");
}else {
System.out.println("欢迎登录");
}
}
}

测试结果截图

存在缺陷

当密码输入为test'or'1'='1时,无论输入什么用户名,都会成功登录进去
原因:打印sql语句 如下图所示
select * from users where name = 'test' and password = 'test'or'1'='1'
and 优先级高于 or ,无论前面是真是假, '1'='1'永远为真
即select语句返回的是真,所有查询返回的是真,虽然密码错误,任然可以登录进去

解决方案

用PreparedStatement类来代替Statement类,同时采用占位符?
可以将缺陷完美解决

加强后的代码 其余代码不变

package com.lanou3g.jdbc;

import java.io.Console;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import com.mysql.jdbc.PreparedStatement;

public class Demo07 {
static {
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
throw new RuntimeException("驱动加载失败");
}
}
static Connection connection = null;
static java.sql.PreparedStatement statement = null;
public static User getUser(String name1,String password1) {
User user = null;
try {
String url = "jdbc:mysql://localhost:3306/myjdbc";
connection = DriverManager.getConnection(url,"root","123456");
String sql = "select * from users where name=? and password=?";
//  对sql语句进行预编译
statement = connection.prepareStatement(sql);
//  给sql语句的占位符 进行赋值
//  参数1 填索引 sql语句中问号索引
statement.setString(1, name1);
statement.setString(2, password1);
System.out.println(sql);
ResultSet resultSet = statement.executeQuery();
//  只返回一条数据
if(resultSet.next()) {
user = new User();
user.setId(resultSet.getInt("id"));
user.setName(resultSet.getString("name"));
user.setPassword(resultSet.getString("password"));
user.setEmail(resultSet.getString("email"));
user.setBirthday(resultSet.getDate("birthday"));
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
if(connection != null) {
try {
connection.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(statement != null) {
try {
statement.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
return user;
}
}

结果截图

注册

表中设置ID为主键,且为自增类型的,实现控制台输入数据,插入到数据库中

代码示例

public class Demo02 {
@Test
public static int test1(String name,String password,String email,String birthday) throws ClassNotFoundException, SQLException {
Class.forName("com.mysql.jdbc.Driver");
String url = "jdbc:mysql://localhost:3306/myjdbc";
Connection connection = DriverManager.getConnection(url,"root","123456");
String sql = "insert into users (name,password,email,birthday) values (?,?,?,?)";
PreparedStatement statement = connection.prepareStatement(sql);
statement.setString(1, "zhangsna");
statement.setString(2,"123");
statement.setString(3, "123@qq.com");
statement.setString(4, "1254-08-01");
int row = statement.executeUpdate();
return row;
}
}

测试类

public class Demo01 {
public static void main(String[] args) throws ClassNotFoundException, SQLException {
Scanner scanner = new Scanner(System.in);
System.out.println("请输入用户名:");
String name = scanner.nextLine();
System.out.println("请输入密码:");
String password = scanner.nextLine();
System.out.println("请输入email:");
String email = scanner.nextLine();
System.out.println("请输入birthday:");
String birthday = scanner.nextLine();
int test1 = Demo02.test1(name, password, email, birthday);
if(test1 > 0) {
System.out.println("注册成功");
}else {
System.out.println("注册失败");
}
}
}