java- fifteen weeks work

Topic 1: write an application, a user name and password to access the test database t_login table (field, including id, username, password), to verify whether the login was successful.

Problem 2: On the basis of a title, if the login is successful, the table t_user information (id, name, sex, birthday) for display (DB.java required to complete the sign and data acquisition operations t_user table), and finally t_user table again add a record operation.

Code:

DB class

package ccut;
import java.sql.*;
public class DB {
    private Connection con;
    private PreparedStatement pre;
    private ResultSet rs;
    private static DB test;
    
    static{
        try{
        Class.forName("com.mysql.jdbc.Driver");
        }catch(ClassNotFoundException e){
            e.printStackTrace();
        }
    }
    
    DB(){
        try{
        con = DriverManager.getConnection("jdbc:mysql://localhost:3306/db","root","");
        }catch(SQLException e){
            e.printStackTrace();
        }
    }
    
    public static DB getInstabce(){
        if(test==null){
            test=new DB();
        }
        return test;
    }
    
    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();
        }
    }

}

test category

package ccut;
import java.util.*;
import java.sql.*;
public class test {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        System.out.println("请输入账号和密码：");
        
         Scanner input=new Scanner(System.in);
            String username=input.next();
            String password=input.next();
            ResultSet a;        
            ResultSet b;        
            DB db = new DB();    
            a = db.executeSelect("select * from t_login where username = '"+username+"' and password = '"+password+"'", args);
            try {
                if (a.next()) {
                    System.out.println("登录成功");
                    System.out.println("以下为t_user表中的信息：");
                    b = db.executeSelect("select * from t_user", args);
                    while(b.next()) {
                        int id = b.getInt (1 );
                        String name= b.getString(2);
                        int sex = b.getInt(3);
                        String birthday = b.getString(4);
                        System.out.println("id:"+id+"\tname:"+name+"\tsex:"+sex+"\tbirthday:"+birthday);    
                    }
                    System.out.println("请输入插入信息：");
                    int id1 = input.nextInt();
                    String name1 = input.next();
                    int sex1 = input.nextInt();
                    String date1 = input.next();
                    String sql="insert into t_user(id,name,sex,birthday) values("+id1+",'"+name1+"',"+sex1+",'"+date1+"')";
                    int n = db.executeModify(sql, args);    
                    if(n>0) {
                        System.out.println("插入成功");
                    }else {
                        System.out.println("插入失败");
                    }
                }else {
                    System.out.println("登陆失败");
                }
            } catch(An SQLException e) { 
                e.printStackTrace (); 
            } 

    } 

}

Screenshot