基于MVC模式的验证码

package com.jb.logon; import java.sql.*; public class UserLogOn { private String username; private String userpassword; private String checknum=""; //生成的验证码 private String getchecknum; //用户输入的验证码 private ResultSet rs; private DB db=new DB(); public UserLogOn(){} public void setUsername(String username){ this.username=username; } public String getUsername(){ return this.username; } public void setUserpassword(String userpassword){ this.userpassword=userpassword; } public String getUserpassword(){ return this.userpassword; } public void makeChecknum(){ String sourcenum="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"; String siglenum=""; String checknum=""; int index=0; int i=0; while(i<4){ index=(int)(Math.random()*100)%35; siglenum=sourcenum.substring(index,index+1); checknum+=siglenum; i++; } this.checknum=checknum; } public String getChecknum(){ return this.checknum; } public void setGetchecknum(String getchecknum){ this.getchecknum=getchecknum; } public String getGetchecknum(){ return this.getchecknum; } public String checkuser(){ String backstr=""; boolean mark=true; if(this.username==null||this.username.equals("")){ backstr+="<li>请输入<b>用户名！</b></li><br>"; mark=false; } if(this.userpassword==null||this.userpassword.equals("")){ backstr+="<li>请输入<b>密&nbsp;&nbsp;码！</b></li><br>"; mark=false; } if(this.getchecknum==null||this.getchecknum.equals("")){ backstr+="<li>请输入<b>验证码！</b></li><br>"; mark=false; } else if(!((this.getchecknum).equals(this.checknum))){ backstr+="<li>输入的<b>验证码</b>不正确！</li><br>随机生成："+this.checknum+"<br>用户输入："+this.getchecknum; mark=false; } if(mark){ String sql="select * from tb_logon where user_name='"+this.username+"' and user_password='"+this.userpassword+"'"; try{ rs=db.getRs(sql); if(!rs.next()) backstr="登录失败！<br>输入的<b>用户名</b>或<b>密码</b>不存在！"; else backstr="登录成功！<br><table><tr><td>用户名：</td><td>"+this.username+"</td></tr><tr><td>密&nbsp;&nbsp;码：</td><td>"+this.userpassword+"</td></tr></table>"; }catch(Exception e){e.printStackTrace();} } db.closed(); return backstr; } }