db.java

简单的银行管理

import java.sql.*;
//对数据库test的操作类
public class DB{

 Connection con=null;
 PreparedStatement ps = null;
 ResultSet rs = null;
     
    public DB() {
     try{
      Class.forName("com.mysql.jdbc.Driver");
      con = DriverManager.getConnection(
       "jdbc:mysql://localhost:3306/test","root","123");  
     }catch(ClassNotFoundException e){
      
     }catch(SQLException e){
      
     }
    }
    
    public boolean login(String username,String password){
     boolean b = false;
     try{
      String sql = "select * from bank_user where name=? and password=?";
      ps = con.prepareStatement(sql);
      ps.setString(1,username);
      ps.setString(2,password);
      rs = ps.executeQuery();
      if(rs.next()){
       b = true;
      }
      else{
       b = false;
      }
     }catch(SQLException e){
      System.out.println (e.getMessage());
     }
     return b;
    }
    
    public double queryBalance(String username,String password){
     double b =0;
  String sql = "select * from bank_user where name=? and password=?";
  try{
   ps = con.prepareStatement(sql);
   ps.setString(1,username);
   ps.setString(2,password);
   rs = ps.executeQuery();
   if(rs.next()){
    b = rs.getDouble("balance");
   }
  }catch(SQLException e){
  }
  return b;
    }
    
    public void getMoney(String username,String password,double amount){
     try{
      String sql = "update bank_user set balance=balance-? where name=? and password=?";
      ps = con.prepareStatement(sql);
      ps.setDouble(1,amount);
      ps.setString(2,username);
      ps.setString(3,password);
      ps.executeUpdate();
     }catch(SQLException e){
     }
    }
    
    public void addMoney(String username,String password,double amount){
     try{
      String sql = "update bank_user set balance=balance+? where name=? and password=?";
      ps = con.prepareStatement(sql);
      ps.setDouble(1,amount);
      ps.setString(2,username);
      ps.setString(3,password);
      ps.executeUpdate();
     }catch(SQLException e){
     }
    }
    public String rework(String username,String repassword)
    {
     try{
      String sql = "update bank_user set password=? where name=?";
      ps = con.prepareStatement(sql);
      ps.setString(1,repassword);
      ps.setString(2,username);
      ps.executeUpdate();
     }catch(SQLException e){
     }
     return repassword;
    }
}