JSP + Servlet实现登录验证码

随机生成四位数验证码，包括汉字，数字，英文大小写。

1.Servlet类

package servlet;

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.AffineTransform;
import java.awt.geom.Line2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class PictureCheckCode extends HttpServlet {

private static final long serialVersionUID = 1L;  

public PictureCheckCode() {  
super();  
        }  

public void destroy() {  
super.destroy();   
        }  

public void init() throws ServletException {  
super.init();  
        }  
/*该方法主要作用是获得随机生成的颜色*/   
public Color getRandColor(int s,int e){  
            Random random=new Random ();  
if(s>255) s=255;  
if(e>255) e=255;  
int r,g,b;  
            r=s+random.nextInt(e-s);    //随机生成RGB颜色中的r值 
            g=s+random.nextInt(e-s);    //随机生成RGB颜色中的g值 
            b=s+random.nextInt(e-s);    //随机生成RGB颜色中的b值 
return new Color(r,g,b);  
        }  

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
        System.out.println("this is doGet method");
this.doPost(request, response);

    }

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

//设置不缓存图片 
        response.setHeader("Pragma", "No-cache");  
        response.setHeader("Cache-Control", "No-cache");  
        response.setDateHeader("Expires", 0);  
//指定生成的响应图片,一定不能缺少这句话,否则错误. 
        response.setContentType("image/jpeg");  
int width=80,height=35;     //指定生成验证码的宽度和高度 
        BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB); //创建BufferedImage对象,其作用相当于一图片 
        Graphics g=image.getGraphics();     //创建Graphics对象,其作用相当于画笔 
        Graphics2D g2d=(Graphics2D)g;       //创建Grapchics2D对象 
        Random random=new Random();  
        Font mfont=new Font("楷体",Font.BOLD,16); //定义字体样式 
        g.setColor(getRandColor(200,250));  
        g.fillRect(0, 0, width, height);    //绘制背景 
        g.setFont(mfont);                   //设置字体 
        g.setColor(getRandColor(180,200));  

//绘制100条颜色和位置全部为随机产生的线条,该线条为2f 
for(int i=0;i<100;i++){  
int x=random.nextInt(width-1);  
int y=random.nextInt(height-1);  
int x1=random.nextInt(6)+1;  
int y1=random.nextInt(12)+1;  
            BasicStroke bs=new BasicStroke(2f,BasicStroke.CAP_BUTT,BasicStroke.JOIN_BEVEL); //定制线条样式 
            Line2D line=new Line2D.Double(x,y,x+x1,y+y1);  
            g2d.setStroke(bs);  
            g2d.draw(line);     //绘制直线 
        }  
//输出由英文，数字，和中文随机组成的验证文字，具体的组合方式根据生成随机数确定。 
        String sRand="";  
        String ctmp="";  
int itmp=0;  
//制定输出的验证码为四位 
for(int i=0;i<4;i++){  
switch(random.nextInt(3)){  
case 1:     //生成A-Z的字母 
                     itmp=random.nextInt(26)+65;  
                     ctmp=String.valueOf((char)itmp);  
break;  
case 2:     //生成汉字 
                     String[] rBase={"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f"};   
//生成第一位区码 
int r1=random.nextInt(3)+11;  
                     String str_r1=rBase[r1];  
//生成第二位区码 
int r2;  
if(r1==13){  
                         r2=random.nextInt(7);     
                     }else{  
                         r2=random.nextInt(16);  
                     }  
                     String str_r2=rBase[r2];  
//生成第一位位码 
int r3=random.nextInt(6)+10;  
                     String str_r3=rBase[r3];  
//生成第二位位码 
int r4;  
if(r3==10){  
                         r4=random.nextInt(15)+1;  
                     }else if(r3==15){  
                         r4=random.nextInt(15);  
                     }else{  
                         r4=random.nextInt(16);  
                     }  
                     String str_r4=rBase[r4];  
//将生成的机内码转换为汉字 
byte[] bytes=new byte[2];  
//将生成的区码保存到字节数组的第一个元素中 
                     String str_12=str_r1+str_r2;  
int tempLow=Integer.parseInt(str_12, 16);  
                     bytes[0]=(byte) tempLow;  
//将生成的位码保存到字节数组的第二个元素中 
                     String str_34=str_r3+str_r4;  
int tempHigh=Integer.parseInt(str_34, 16);  
                     bytes[1]=(byte)tempHigh;  
                     ctmp=new String(bytes);  
break;  
default:  
                     itmp=random.nextInt(10)+48;  
                     ctmp=String.valueOf((char)itmp);  
break;  
            }  
            sRand+=ctmp;  
            Color color=new Color(20+random.nextInt(110),20+random.nextInt(110),random.nextInt(110));  
            g.setColor(color);  
//将生成的随机数进行随机缩放并旋转制定角度 PS.建议不要对文字进行缩放与旋转,因为这样图片可能不正常显示 
/*将文字旋转制定角度*/  
            Graphics2D g2d_word=(Graphics2D)g;  
            AffineTransform trans=new AffineTransform();  
            trans.rotate((45)*3.14/180,15*i+8,7);  
/*缩放文字*/  
float scaleSize=random.nextFloat()+0.8f;  
if(scaleSize>1f) scaleSize=1f;  
            trans.scale(scaleSize, scaleSize);  
            g2d_word.setTransform(trans);  
            g.drawString(ctmp, 15*i+18, 14);  
        }  
        HttpSession session=request.getSession(true);  
        session.setAttribute("randCheckCode", sRand);  
        System.out.println(sRand);
        g.dispose();    //释放g所占用的系统资源 
        ImageIO.write(image,"JPEG",response.getOutputStream()); //输出图片 
    }

}

2.web.xml配置

<servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>PictureCheckCode</servlet-name>
    <servlet-class>servlet.PictureCheckCode</servlet-class>
  </servlet>

<servlet-mapping>
    <servlet-name>PictureCheckCode</servlet-name>
    <url-pattern>/pictureCheckCode</url-pattern>
  </servlet-mapping>

3.jsp页面输出验证码

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>

<title>登录页面</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<script language="javascript">
function myReload() {
 document.getElementById("CreateCheckCode").src = document
 .getElementById("CreateCheckCode").src
 + "?nocache=" + new Date().getTime();
 }
</script>

</head>

<body>
<form action="loginServlet" method="get">
<p class="font tdheight">
                验证码：<input type="text" name="checkCode"
style="width:70px;height:35px;"> <img
 src="pictureCheckCode" id="CreateCheckCode" align="middle"
style="margin-top:-10px;"> <br> <a href=""
onclick="myReload()"
style="font-size:12px;color:red;margin-left:156px;"> 看不清,换一个</a>
</p>
<br><input type="submit" value="提交"
class="font" style="width:240px;height:35px;background:#f19e28">

</form>
</body>
</html>

4.后台Servlet判断验证码是否与输入一致
通过request.getParameter(“checkCode”)获取输入验证码，与session.getAttribute(“randCheckCode”)比较是否一致。

public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

String code = request.getParameter("checkCode");
        HttpSession session = request.getSession();
if (!code.equals(session.getAttribute("randCheckCode"))) {
request.setAttribute("errormsg", "验证码不正确");
        } 
        System.out.println(request.getAttribute("errormsg"));
    }

运行结果：