用户登录小程序

在数据库建一个表格存入诺干用户跟用户密码，id自增

程序不长就写在一个class里面啦
里面涉及到的JDBC相关的类跟方法详见上一篇，有详细解释

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

import com.mysql.jdbc.PreparedStatement;

public class TestStatement {
    static Scanner sc=new Scanner(System.in);
    public static void main(String[] args) {
        System.out.println("请输入用户名：");
        String name=sc.nextLine();
        System.out.println("请输入密码：");
        String password =sc.nextLine();
        User user=isExist(name, password);
        if(user!=null){
            System.out.println("登录成功");
        }
        else{
            System.out.println("登录失败");
        }
    }
    //获取连接
  public static Connection getConnection(){
      String driver="com.mysql.jdbc.Driver";//mysql的Driver
      String url="jdbc:mysql://localhost:3306/test";//数据库的位置
      String user="root";
      String password="123456";
      Connection conn=null;
    try {
        Class.forName(driver);//加载注册驱动
    conn = DriverManager.getConnection(url,user,password);
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (SQLException e) {
        e.printStackTrace();
    }
      return conn;
  }
  //判断输入的用户名跟密码是否存在
  public static User isExist(String name,String password){
      String sql="select *from user where name=? and password=?";
      Connection conn=null;
    PreparedStatement ps=null;
    ResultSet rs=null;
     User user=null;
    try {
        conn = getConnection();
          ps = (PreparedStatement) conn.prepareStatement(sql);//PreparedStatement对象用于执行sql语句
          ps.setString(1, name);//给占位符？赋值
          ps.setString(2, password);//给占位符？赋值
          rs = ps.executeQuery();//结果集对象     
          while(rs.next()){
              user=new User();
              user.setId(rs.getInt(1));
              user.setName(rs.getString(2));
              user.setPassword(rs.getString(3));      
          }
    } catch (SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    finally{
        if(rs!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
       if(ps!=null){
           try {
            ps.close();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        }
       if(conn!=null){
              try {
                conn.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

}
    }

     return user;  
  }
}
//用户类
class User{
    private int id;
    private String name;
    private String password;
    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 int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    @Override
    public String toString() {
        return "User [id=" + id + ", name=" + name + ", password=" + password + "]";
    }
    public User(int id, String name, String password) {
        super();
        this.id = id;
        this.name = name;
        this.password = password;
    }
    public User() {

    }

}

结果如下
输入正确与不正确时：