第十五次作业

题目1：编写一个应用程序，输入用户名和密码，访问test数据库中t_login表（字段包括id、username、password），验证登录是否成功。

package cn.edu.ccut.po8;
import java.sql.*;

import java.util.Scanner;
public class Tast1 {
    public static void main(String[] args) {
        
        Connection con=null;
        Statement st=null;
        ResultSet rs=null;
        Scanner sc=new Scanner(System.in);
        System.out.println("请输入用户名");
        String username=sc.next();
        System.out.println("请输入密码");
        String password=sc.next();
      
    try {
        Class.forName("com.mysql.jdbc.Driver");
        String url="jdbc:mysql://localhost:3306/db";
            con=DriverManager.getConnection(url ,"root","root");   
            String sql="select * from t_login where username='"+username+"'and password='"+password+"'";
            st=con.createStatement();       
            rs=st.executeQuery(sql);
            if(username.equalsIgnoreCase(username)&&password.equalsIgnoreCase(password)){
                System.out.println("success");
            }else{
                System.out.println("fail");
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
     catch (ClassNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}
}

运行截图

题目2：在上一题基础上，当登录成功后，将t_user表（id、name、sex、birthday）的信息进行显示（要求使用DB.java完成登录和获取t_user表中数据的操作），最后再对t_user表进行一条记录的添加操作。

1.DB类

package cn.edu.ccut.po8;
import java.sql.*;
public class DB {
    private Connection con;
    private PreparedStatement pre;
    private ResultSet rs;
    private static DB db;
    
    static
    {
         try {
           Class.forName("com.mysql.jdbc.Driver");
        } 
         catch (ClassNotFoundException e) {
          e.printStackTrace();
        }
    }
    private DB()
    {
        try {
            con=DriverManager.getConnection("jdbc:mysql://localhost:3306/db?useSSL=false", "root","1234");
        } catch (SQLException e) {
            e.printStackTrace();
        }
        
    }
    public static DB getInstance() {
        if(db==null)
            db=new DB();
         return db;
    }
     public ResultSet executeSelect(String sql,Object[] args){
        try {
            pre=con.prepareStatement(sql);
            if(args.length!=0)
            {
                for(int i=0;i<args.length;i++)
                {
                    pre.setObject(i+1, args[i]);
                }
            }
            rs=pre.executeQuery();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return rs;
    }
     public int executeModify(String sql,Object[] args)
     {
         int n=0;
         try {
             pre=con.prepareStatement(sql);
             if(args.length!=0)
             {
                for(int i=0;i<args.length;i++)
                {
                    pre.setObject(i+1, args[i]);
                }
             }
             n=pre.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return n;
     }
     public void close(){
            try {
                 if(rs!=null)
                    rs.close();
                 pre.close();
                 con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
         
     }
    
}

2、测试类

package cn.edu.ccut.po8;
import java.sql.*;
import java.util.*;
public class Tast {
     public static void main(String[] args) {
            System.out.println("请输入用户名：");
            Scanner reader1=new Scanner(System.in);
            String name=reader1.nextLine();
            System.out.println("请输入密码：");
            Scanner reader2=new Scanner(System.in);
            String word=reader2.nextLine();
            Connection con=null;
            Statement st=null;
            ResultSet rs=null;
            try {
                    Class.forName("com.mysql.jdbc.Driver");  // 加载JDBC驱动程序
                    con=DriverManager.getConnection("jdbc:mysql://localhost:3306/db?useSSL=false",
                                                    "root",""); //建立与数据库的连接
                    st=con.createStatement();  //创建一个执行SQL语句的对象
                    String sql="select * from t_login where username='"+name+"'and password='"+word+"'";  //SQL语句
                    rs=st.executeQuery(sql); //查询语句
                    if(rs.next())
                    {
                        System.out.println("登录成功！");
                        System.out.println("显示列表信息");
                        rs=DB.getInstance().executeSelect("select * from t_user", args);            
                        while(rs.next()){    
                            System.out.println("姓名:"+rs.getString(2)+"  性别:"+rs.getString(3)+"  生日:"+rs.getString(4));    
                        }
                        System.out.println("添加信息");
                        System.out.println("请输入姓名:");
                        Scanner reader=new Scanner(System.in);
                        String name1=reader.nextLine();
                        System.out.println("请输入性别:");
                        String sex=reader.nextLine();  
                        System.out.println("请输入出生日期:");
                        String birthday =reader.nextLine();
                        String newsql="insert into t_user (name,sex,birthday) values ('"+name1+"','"+sex+"','"+birthday+"')";

                        int n=DB.getInstance().executeModify(newsql, args);
                        if(n>0){
                            System.out.println("添加成功");

                        }else{
                            System.out.println("添加失败");

                        }
                    }
                    else
                    {
                       System.out.println("登录失败");

                    }

             } catch (ClassNotFoundException e) {
                e.printStackTrace();
             } catch (SQLException e) {
                e.printStackTrace();
             }
             finally
             {
                try {
                    st.close();   //依次关闭数据库连接
                    con.close(); 
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }

3、运行截图