【学习笔记⑦】登录页面怎样实现验证码登录功能

     用户登录时，有需要填写验证码的需求，而怎样用java代码实现的呢，以下是实现该工能的代码.

1.验证码随机生成方法，方法封装在RandomPic.java文件中，代码如下：

package com.qidian.util;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.Random;

public class RandomPic
{
private final int width=60;
private final int height=20;

private final int interfereLineNum = 88;
private final int interferePointNum = 88;
private final int interfereLineLenMax = 12;
private final int authenticationCodeNumber = 4;

private final int backgroundColorBegin =200;
private final int backgroundColorFinal =250;

private final int interfereColorBegin =160;
private final int interfereColorFinal =200;

private final int radomNumberColorBegin =20;
private final int radomNumberColorFinal =130;

private final String fontName="Times New Roman";
private final int fontStyle = Font.PLAIN;
private final int fontSize = 18;

private final int stringWidth =13;
private final int stringHight =16;
private final int stringClearance =6;

private final int rgbValue = 255;

private Graphics graphics;

public String authenticationCode=new String();
public BufferedImage image;


public RandomPic(){
init();
}

public RandomPic(String rn){
init();
authenticationCode = rn;
}

private void init(){
image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
graphics = image.getGraphics();
}
public void drawServer(){

drawBasic();

drawInterfereLine();

drawRadomNumberServer();

graphics.dispose();
}
public void drawClient(){

drawBasic();

drawInterfereLine();


drawRadomNumberClient();

graphics.dispose();
}

private Color getRandColor(int fc,int bc){
Random random = new Random();
if(fc>rgbValue) fc=rgbValue;
if(bc>rgbValue) bc=rgbValue;
int r=fc+random.nextInt(bc-fc);
int g=fc+random.nextInt(bc-fc);
int b=fc+random.nextInt(bc-fc);
return new Color(r,g,b);
}


private void drawBasic(){

graphics.setColor(getRandColor(backgroundColorBegin,backgroundColorFinal));
graphics.fillRect(0, 0, width, height);

graphics.setFont(new Font(fontName,fontStyle,fontSize));

graphics.setColor(new Color(rgbValue,rgbValue,rgbValue));
graphics.drawRect(0,0,width-1,height-1);
}

private void drawInterfereLine(){
Random random = new Random();
graphics.setColor(getRandColor(interfereColorBegin,interfereColorFinal));
for (int i=0;i<interfereLineNum;i++){
int x = random.nextInt(width);
int y = random.nextInt(height);
int xl = random.nextInt(interfereLineLenMax);
int yl = random.nextInt(interfereLineLenMax);
graphics.drawLine(x,y,x+xl,y+yl);
}
}

@SuppressWarnings("unused")
private void drawInterferePoint(){
Random random = new Random();
graphics.setColor(getRandColor(interfereColorBegin,interfereColorFinal));
for (int i=0;i<interferePointNum;i++){
int x = random.nextInt(width);
int y = random.nextInt(height);
graphics.drawLine(x,y,x,y);
}
}

private void drawRadomNumberServer(){
Random random = new Random();
for (int i=0;i<authenticationCodeNumber;i++){
String rand=String.valueOf(random.nextInt(10));
authenticationCode+=rand;
graphics.setColor(getRandColor(radomNumberColorBegin,radomNumberColorFinal));

graphics.drawString(rand,stringWidth*i+stringClearance,stringHight);
}
}
 private void drawRadomNumberClient(){
authenticationCode = authenticationCode.substring(0,authenticationCode.indexOf("."));
switch(authenticationCode.length()){
   case 1: authenticationCode = "000"+authenticationCode; break;
   case 2: authenticationCode = "00"+authenticationCode; break;
   case 3: authenticationCode = "0"+authenticationCode; break;
   default: authenticationCode = authenticationCode.substring(0,4); break;
}
graphics.setColor(getRandColor(radomNumberColorBegin,radomNumberColorFinal));
graphics.drawString(authenticationCode,stringWidth,stringHight);
 }
}

   2.调用RandomPic对象，实现功能，写在单独的checkPic.jsp页面，代码如下：

<%@ page contentType="image/jpeg"
 import="java.awt.image.*,
         javax.imageio.*,
         com.sias.qidian.education.util.RandomPic,
         java.io.*"%>
<%
 response.setHeader("Pragma", "No-cache");
 response.setHeader("Cache-Control", "no-cache");
 response.setDateHeader("Expires", 0);
 double rand = Math.random() * 10000;
 RandomPic rp = new RandomPic(Double.toString(rand));
 rp.drawClient();
 session.setAttribute("checkPic", rp.authenticationCode);//通过session传递，然后后台接受判断是否正确
 BufferedImage image = rp.image;
 OutputStream output=response.getOutputStream();
 try 
 {
  ImageIO.write(image, "JPEG", output);
 } catch (IOException e) {
  e.printStackTrace();
 }finally{
 	output.flush();
 	output.close();
 	output=null;
 	response.flushBuffer();
 	out.clear();
 	out = pageContext.pushBody();
 }
 
%>

3.在login.jsp页面编写html代码，通过input标签实现，代码如下：

           <td>  验证码：<input name="checkPic" type="text" maxLength=4 size=8>
              <img border='0' src='<%=basePath %>commons/checkPic.jsp'/></td>

4.在servlet中进行登录判断，代码如下：

以上步骤是实现用户验证码验证功能。