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。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。

TestMain类

package ccut.ch.fifteen;
import java.sql.*;
import java.util.Scanner;

public class TestMain {
    public static void main(String[] args) {
        Scanner r = new Scanner(System.in);
        System.out.println("请输入用户名和密码:");
        String  username = r.next();
        String password = r.next();
        Connection con = null;
        Statement st = null;
        ResultSet rs=null;

        try {
            Class.forName("com.mysql.jdbc.Driver");
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/db","root","");
            st = con.createStatement();
            String sql ="insert into t_login(username,password) values('" +username+ "','" + password + "')";

            int count =st.executeUpdate(sql); 
            if(count>0) {
                System.out.println("登陆成功");
                rs= DB.getInstance().executeSelect("select * from t_user", args);	//调用方法，查询表中信息

                while(rs.next()) {  //循环输出
                    int id = rs.getInt(1);
                    String name = rs.getString(2);
                    int sex = rs.getInt(3);
                    String birthday = rs.getString(4);
                    System.out.println("id	"+"name	"+"sex	"+"birthday");
                    System.out.println(id + "	" + name + "	" + sex + "	" + birthday);
                }
                
                
                System.out.println("请输入id，name，sex，birthday：");//增加一条记录
                String id=r.next();
                String name=r.next();
                Integer sex = Integer.valueOf(r.next());
                String birthday = r.next();
                String sql1="insert into t_user(id,name,sex,birthday) values('"+id+"','"+name+"','"+sex+"','"+birthday+"')";
                int Count=DB.getInstance().executeModify(sql1, args);
                if(Count>0)
                    System.out.println("添加成功");
                else
                    System.out.println("添加失败,填写有误");
            }
            else
                System.out.println("登陆失败");


        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        }finally {
            try {
                st.close();
                con.close();
            }catch (SQLException e){
                e.printStackTrace();
            }
        }
    }
}

DB类

package ccut.ch.fifteen;
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");  //加载JDBC驱动程序
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    private DB(){   //DB构造方法
        try {
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/db","root",""); //创建数据库的连接
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public static DB getInstance(){
        if(db == null){
            db = new DB();
        }
        return  db;
    }
    public ResultSet executeSelect(String sql,Object[] args){   //查询
        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) {//更新
        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() {   //关闭数据库连接
        try {
            if (rs != null) {
                rs.close();
            }
            pre.close();
            con.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

运行结果