//validationCode类。

package com.validationCode;

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.util.Random;

import javax.imageio.ImageIO;

import javax.servlet.ServletException;

import javax.servlet.ServletOutputStream;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

public class ValidateCodeServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

private static int WIDTH = 65;//设置图片的宽度

private static int HEIGHT = 22;//设置图片的高度

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

HttpSession session = request.getSession();

response.setContentType("image/jpeg");

ServletOutputStream sos = response.getOutputStream();

response.setHeader("Pragma", "No-cache");

response.setHeader("Cache-Control", "no-cache");

response.setDateHeader("Expires", 0);

BufferedImage image = new BufferedImage(WIDTH, HEIGHT,

BufferedImage.TYPE_INT_RGB);

Graphics g = image.getGraphics();

char[] rands = generateCheckCode();

drawBackground(g);

drawRands(g, rands);

g.dispose();

ByteArrayOutputStream bos = new ByteArrayOutputStream();

ImageIO.write(image, "JPEG", bos);

byte[] buf = bos.toByteArray();

response.setContentLength(buf.length);

sos.write(buf);

bos.close();

sos.close();

session.setAttribute("randomCode", new String(rands));

}

private void drawBackground(Graphics g) {

g.setColor(new Color(0xDCDCDC));

g.fillRect(0, 0, WIDTH, HEIGHT);

for (int i = 0; i < 120; i++) {

int x = (int) (Math.random() * WIDTH);

int y = (int) (Math.random() * HEIGHT);

int red = (int) (Math.random() * 255);

int green = (int) (Math.random() * 255);

int blue = (int) (Math.random() * 255);

g.setColor(new Color(red, green, blue));

g.drawOval(x, y, 1, 0);

}

}

private void drawRands(Graphics g, char[] rands) {

// g.setColor(Color.BLUE);

Random random = new Random();

int red = random.nextInt(110);

int green = random.nextInt(50);

int blue = random.nextInt(50);

g.setColor(new Color(red, green, blue));

g.setFont(new Font(null, Font.ITALIC | Font.BOLD, 18));

g.drawString("" + rands[0], 1, 17);

g.drawString("" + rands[1], 16, 15);

g.drawString("" + rands[2], 31, 18);

g.drawString("" + rands[3], 46, 16);

}

private char[] generateCheckCode() {

String chars = "13456789ABCDEFGHIJKLMNPQRSTUVWXY";

char[] rands = new char[4];

for (int i = 0; i < 4; i++) {

int rand = (int) (Math.random() * 32);

rands[i] = chars.charAt(rand);

}

return rands;

}

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

this.doGet(request, response);

}

}

//在servlet中判断输入验证码是否正确

 

validate=request.getParameter("random");

HttpSession session = request.getSession();

String randomCode = (String)session.getAttribute("randomCode");

if(validate.equalsIgnoreCase(randomCode)){

//如果正确就。。。。。

}

else{

request.getSession().setAttribute("errorMessage",

"验证码不匹配，请重新输入验证码!");

}

//jsp页面

<script  language="javascript">

function changeCode()

{

document.getElementById('rc').src="imgcode?t="+new Date().getTime();

}

</script>

<div>

<img src="imgcode" id="rc"/>

<input type="text" name="random" maxlength="4"/>

<a href="javascript:changeCode();">看不清？单击换一张图片</a>

</div>

//web.xml

 

<servlet>

<servlet-name>ValidateCodeServlet</servlet-name>

<servlet-class>com.validationCode.ValidateCodeServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>ValidateCodeServlet</servlet-name>

<url-pattern>/imgcode</url-pattern>

</servlet-mapping>