【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。