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。

代码

package cc;
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();
            }
        }
        public DB() {
            try {
                con = DriverManager.getConnection("jdbc:mysql://localhost:3306/st","root","");
            } 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 = (PreparedStatement) 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 = (PreparedStatement) 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();
            }
        }
        }

package cc;
import java.util.*;
import java.sql.*;
import cc.DB;
public class Login {
    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        System.out.println("请输入用户名为:");
        String username = s.next();
        System.out.println("请输入密码为:");
        String password= s.next();
        ResultSet prove;        
        ResultSet r;        
        DB db = new DB();    
        prove = db.executeSelect("select * from t_login where username = '"+username+"' and password = '"+password+"'", args);    
        try {
            if (prove.next()) {
                System.out.println("登录成功");
                System.out.println("显示t_user表中的信息为:");
                r = db.executeSelect("select * from t_user", args);        
                while(r.next()) {
                    int id = r.getInt(1);
                    String name = r.getString(2);
                    int sex = r.getInt(3);
                    String birthday =r.getString(4);
                    System.out.println("id:"+id+"	name:"+name+"	sex:"+sex+"	birthday:"+birthday);    
                }
                System.out.println("请输入需要添加的记录内容为：");
                int new_id = s.nextInt();
                String newname = s.next();
                int newsex = s.nextInt();
                String newdate =s.next();
                String sql="insert into t_user(id,name,sex,birthday) values("+new_id+",'"+newname+"',"+newsex+",'"+newdate+"')";    
                int n =db.executeModify(sql, args);    
                if(n>0) {
                    System.out.println("数据插入成功");
                }else {
                    System.out.println("数据插入失败");
                }
            }else {
                System.out.println("登陆失败");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

运行结果