java使用servlet实现验证码

利用servlet 实现验证码主要继承httpServlet类

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package com.zyc.demo;

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.io.IOException;

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 DrewImage extends HttpServlet{

/**

*

*/

private static final long serialVersionUID = 1505032428319459075L;

private final Font mFont =

new Font("Arial Black", Font.PLAIN, 16);

private final int IMG_WIDTH = 100;

private final int IMG_HEIGTH = 18;

private Color getRandColor(int fc,int bc)

{

Random random = new Random();

if(fc > 255) fc = 255;

if(bc > 255) bc=255;

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);

}

public void service(HttpServletRequest request,

HttpServletResponse response)

throws ServletException, IOException

{

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

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

response.setDateHeader("Expires", 0);

response.setContentType("image/jpeg");

BufferedImage image = new BufferedImage

(IMG_WIDTH , IMG_HEIGTH , BufferedImage.TYPE_INT_RGB);

Graphics g = image.getGraphics();

Random random = new Random();

g.setColor(getRandColor(200 , 250));

g.fillRect(1, 1, IMG_WIDTH - 1, IMG_HEIGTH - 1);

g.setColor(new Color(102 , 102 , 102));

g.drawRect(0, 0, IMG_WIDTH - 1, IMG_HEIGTH - 1);

g.setColor(getRandColor(160,200));

for (int i = 0 ; i < 30 ; i++)

{

int x = random.nextInt(IMG_WIDTH - 1);

int y = random.nextInt(IMG_HEIGTH - 1);

int xl = random.nextInt(6) + 1;

int yl = random.nextInt(12) + 1;

g.drawLine(x , y , x + xl , y + yl);

}

g.setColor(getRandColor(160,200));

for (int i = 0 ; i < 30 ; i++)

{

int x = random.nextInt(IMG_WIDTH - 1);

int y = random.nextInt(IMG_HEIGTH - 1);

int xl = random.nextInt(12) + 1;

int yl = random.nextInt(6) + 1;

g.drawLine(x , y , x - xl , y - yl);

}

g.setFont(mFont);

String sRand = "";

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

{

String tmp = getRandomChar();

sRand += tmp;

g.setColor(new Color(20 + random.nextInt(110)

,20 + random.nextInt(110)

,20 + random.nextInt(110)));

g.drawString(tmp , 15 * i + 10,15);

}

HttpSession session = request.getSession(true);

session.setAttribute("rand" , sRand);

// System.out.println("写入session"+sRand);

g.dispose();

ImageIO.write(image, "JPEG", response.getOutputStream());

}

private String getRandomChar()

{

int rand = (int)Math.round(Math.random() * 2);

long itmp = 0;

char ctmp = '\\u0000';

switch (rand)

{

case 1:

itmp = Math.round(Math.random() * 25 + 65);

ctmp = (char)itmp;

return String.valueOf(ctmp);

case 2:

itmp = Math.round(Math.random() * 25 + 97);

ctmp = (char)itmp;

return String.valueOf(ctmp);

default :

itmp = Math.round(Math.random() * 9);

return itmp + "";

}

下面是web.xml 配置

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">

<display-name>IndustryDemo</display-name>

<welcome-file-list>

<welcome-file>index.html</welcome-file>

<welcome-file>index.htm</welcome-file>

<welcome-file>index.jsp</welcome-file>

<welcome-file>default.html</welcome-file>

<welcome-file>default.htm</welcome-file>

<welcome-file>default.jsp</welcome-file>

</welcome-file-list>

<servlet>

<servlet-name>img</servlet-name>

<servlet-class>com.zyc.demo.DrewImage</servlet-class>