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。
DB类
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; private ResultSet rs; private static DB test; static { try { Class.forName("com.mysql.jdbc.Driver"); } catch (ClassNotFoundException e) { e.printStackTrace(); } } private DB() { try { con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root",""); } catch (SQLException e) { e.printStackTrace(); } } public static DB getInstance() { 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(); } } }
Testmain类
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"); try { con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root",""); } catch (SQLException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } try { st = con.createStatement(); } catch (SQLException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } String sql ="insert into t_login(username,password) values('" +username+ "','" + password + "')"; int count = 0; try { count = st.executeUpdate(sql); } catch (SQLException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } 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 try { 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); } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } 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 e) { e.printStackTrace(); }finally { try { st.close(); con.close(); }catch (SQLException e){ e.printStackTrace(); } } } }
运行截图