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。

源代码：

1.DB.java

package demo;
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/test","root","123");
            } 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.test.java

package demo;
 
import java.sql.*;

import java.util.Scanner;

public class test {
 
    public static void main(String[] args) {
      
        Scanner scanner=new Scanner(System.in);//创建一个输入对象
        String username=scanner.next();//控制台输入一个String类型的username
        String password=scanner.next();//控制台输入一个String类型的password
        Connection con=null;//定义数据库连接对象con
        Statement st=null;//定义SQL语句执行对象st
        ResultSet rs=null;//定义SQL语句执行对象rs
        ResultSet rs1=null;//定义SQL语句执行对象rs1
        try {
            DriverManager.registerDriver(new com.mysql.jdbc.Driver());
           
            con=DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","123");
            //建立数据库的连接
            st=con.createStatement(); //创建SQL语句执行对象st
 
             String sql = "select * from t_login where username='" + username+ "' and password = '" + password + "'";
           
             rs=st.executeQuery(sql); //查询sql语句中的username和password
             boolean bl=rs.next();
             if(bl) {
                 System.out.println("登陆成功");
                rs1= DB.getInstance().executeSelect("select * from t_user", args);//预处理
                while(rs1.next()) {
                    int id = rs1.getInt(1);
                    String name = rs1.getString(2);
                    String sex = rs1.getString(3);
                    String birthday = rs1.getString(4);
                    System.out.println("id       name        sex      birthday");
                    System.out.println(id + "       " + name + "       " + sex + "      " + birthday);
                }
                System.out.println("添加信息");
                int id=scanner.nextInt();
                String name=scanner.next();
                String sex=scanner.next();
                String birthday=scanner.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("数据添加成功");
                else
                    System.out.println("数据添加失败");
             }
             else {
                 System.out.println("登陆失败");
             }
        } catch (SQLException e) {           
            e.printStackTrace();
        }finally {
            try {
                st.close();
            } catch (SQLException e) {               
                e.printStackTrace();
            }
            try {
                con.close();
            } catch (SQLException e) {              
                e.printStackTrace();
            }
        }
    }
 
}

运行结果：