userdao.java

我做的第一个java MIS项目

package server.dao;
import java.sql.*;
import server.dao.Connectionmanager;
import server.entity.User;
import java.util.*;

//帐户数据对象
public class Userdao {

    private Connection con = null;
    private Connectionmanager cm=null;
    private PreparedStatement ps = null;
    private ResultSet rs = null;

    //检验帐户的有效性
    public boolean chk(User user)
    {
        //初始化变量
        String testusername=user.getusername();
        String testuserpwd=user.getuserpwd();
        String dbusername=null;
        String dbuserpwd=null;
        //创建一个连接并得到查询结果
        cm =new Connectionmanager();
        con= cm.getconnection();
        try
        {
            ps = con.prepareStatement("select * from [user] where userid='" +user.getusername() + "'");
            rs=ps.executeQuery();
            while(rs.next())
            {
                dbusername=rs.getString(1);
                dbuserpwd=rs.getString(2);
            }
        }
        catch (SQLException ex) {return false;}
        //断开数据连接
        finally
        {
            cm.closeresultset(rs);
            cm.closestatement(ps);
            cm.closeconnection(con);
        }

        //判断并返回判断值
        if (dbusername.equals(user.getusername())&& dbuserpwd.equals(user.getuserpwd()) )
        {return true;}
        else
        {return false;}
    }

    //得到所有用户名
    public Vector getallusername()
    {
        //初始化变量
        Vector allusername=new Vector();
        //创建一个连接并得到查询结果
        cm =new Connectionmanager();
        con= cm.getconnection();
        try
        {
            ps = con.prepareStatement("select userid from [user]");
            rs = ps.executeQuery();
            while (rs.next()) {allusername.addElement(rs.getString(1));}
        }
        catch (SQLException ex) {}
        //断开数据连接
        finally
        {
            cm.closeresultset(rs);
            cm.closestatement(ps);
            cm.closeconnection(con);
        }
        //返回值
        return allusername;
    }


    //得到所有用户密码
    public Vector getalluserpwd()
    {
        //初始化变量
        Vector alluserpwd=new Vector();
        //创建一个连接并得到查询结果
        cm =new Connectionmanager();
        con= cm.getconnection();
        try
        {
            ps = con.prepareStatement("select userpwd from [user]");
            rs = ps.executeQuery();
            while (rs.next()) {alluserpwd.addElement(rs.getString(1));}
        }
        catch (SQLException ex) {}
        //断开数据连接
        finally
        {
            cm.closeresultset(rs);
            cm.closestatement(ps);
            cm.closeconnection(con);
        }
        //返回值
        return alluserpwd;
    }


    //更新用户密码
    public void setuserpwd(String userid,String userpwd)
   {
       //创建一个连接并得到查询结果
       cm =new Connectionmanager();
       con= cm.getconnection();
       try
       {
           ps = con.prepareStatement("update [user]  set userpwd='"+userpwd+"' where userid='"+userid+"'");
           rs = ps.executeQuery();
       }
       catch (SQLException ex) {}
       //断开数据连接
       finally
       {
           cm.closeresultset(rs);
           cm.closestatement(ps);
           cm.closeconnection(con);
       }
   }

}