第15周作业

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 test;

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

/*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。*/
public class test {

    public static void main(String[] args) {
        Scanner reader = new Scanner(System.in);
        System.out.print("请输入用户名和密码:\n");
        String username = reader.nextLine();
        String password = reader.nextLine();
        Connection con = null;
        PreparedStatement ps = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "");
            ps = con.prepareStatement("select * from t_login  where username=? and password=?");
            ps.setString(1, username);
            ps.setString(2, password);
            ResultSet rs = ps.executeQuery();
            if (rs.next()) {
                System.out.print("yes");
            } else {
                System.out.print("no");
            }
            if (rs != null) {
                rs.close();
            }

        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                ps.close();
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

运行结果：

 

 

 

 

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.Java

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
 
public class DB {
    private Connection con;
    private PreparedStatement pre;
    ResultSet rs;
    private static DB db;
    public static DB getInstance() {                //无参构造方法
        if(db ==null) {
            db = new DB();
        }
        return db;
         
    }
 
    DB(){
        try {
            con = DriverManager.getConnection(
                    "jdbc:mysql://localhost:3306/test","root","0000");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }   
    static {
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    public ResultSet executeSelect(String sql,Object[] args) {   //查询数据方法
        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 executeUpdate(String sql,Object[] args) {        //修改数据
        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) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
         
    }
 
}

2.test.Java

import java.sql.SQLException;
import java.util.Scanner;
public class Test {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.println("请输入用户名");
        String username = in.next();
        System.out.println("请输入用户名");
        String password = in.next();
        Object []a = {username, password};
        String sql = "select * from  t_login where username=? and password=?";
        DB db = DB.getInstance();                       //创建DB对象
        db.executeSelect(sql, a);
        try {
            if(db.rs.next()){
                System.out.println("登陆成功!");
                Object []b = new Object[0];
                sql = "select * from t_user ";
                db.executeSelect(sql, b);       
                while(db.rs.next()){                    //显示t_user表内容;
                    String name = db.rs.getString(2);
                    String sex = db.rs.getString(3);
                    String birthday = db.rs.getString(4);
                    System.out.println("姓名:"+name+" 性别:"+sex+" 生日 :"+birthday+"");
                }
                System.out.println("请输入新记录:");
                String newname = in.next();
                String newsex = in.next();
                String newbirthday = in.next();
                Object []c = {newname, newsex , newbirthday};
                sql = "insert into t_user (name,sex,birthday) values(?,?,?)";
                int count = db.executeUpdate(sql, c); //添加记录;
                if(count == 0){
                    System.out.println("失败!");
                }else{
                    System.out.println("成功");
                }
            }else{
                System.out.println("失败");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
 
}

运行结果：