Java 随机生成验证码(支持大小写字母、数字、随机字体)的实例

代码如下所示：

复制代码代码如下:

package com.hoo.util;

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.util.Random;

import javax.imageio.ImageIO;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

* function: 验证码生成工具类

* @project NetWorkService

* @package com.hoo.util

* @fileName ValidCodeUtils.java

* @createDate 2010-8-3 下午03:05:50

* @author hoojo

@SuppressWarnings("unused")

public class ValidCodeUtils {

/*********************************************************************

* 验证码宽度

public static int WIDTH = 60;

/***

* 验证码高度

public static int HEIGHT = 20;

/**********************************************************************

* 验证码背景颜色COLOR_FC_BG 应当小于COLOR_BC_BG

public static int COLOR_FC_BG = 200;

/***

* 验证码背景颜色COLOR_FC_BG 应当小于COLOR_BC_BG

public static int COLOR_BC_BG = 250;

/**********************************************************************

* 验证码背景干扰线颜色COLOR_FC_LINE 应当小于COLOR_BC_LINE

public static int COLOR_FC_LINE = 160;

/***

* 验证码背景干扰线颜色COLOR_FC_LINE 应当小于COLOR_BC_LINE

public static int COLOR_BC_LINE = 200;

/***************************************************************************

* 验证码颜色COLOR_FC_CODE 应当小于COLOR_BC_CODE

public static int COLOR_FC_CODE = 20;

/***

* 验证码颜色COLOR_FC_CODE 应当小于COLOR_BC_CODE

public static int COLOR_BC_CODE = 170;

/***************************************************************************

* 生成在指定范围内的颜色

* @param fc 范围fc color值小于255

* @param bc 范围bc color值小于255

* @return Color

private static Color getRandColor(int fc, int bc) {

Random random = new Random();

if (fc < 0)

fc = 0;

if (bc < 0)

bc = 1;

if (fc > 255)

fc = 255;

if (bc > 255)

bc = 255;

if (bc == fc)

bc += 10;

int temp = 0;

if (bc < fc) {

temp = bc;

bc = fc;

fc = temp;

}

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);

}

/**

* function: 生成图片方法

* @createDate 2010-8-3 下午03:06:22

* @author hoojo

* @param request HttpServletRequest

* @param response HttpServletResponse

* @return boolean

* @throws Exception

public static boolean getImage(HttpServletRequest request, HttpServletResponse response) throws Exception{

response.reset();

response.setContentType("image/jpeg");

// 设置页面不缓存

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

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

response.setDateHeader("Expires", 0);

// 在内存中创建图象

BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);

// 获取图形上下文

Graphics img = image.getGraphics();

// 生成随机类

Random random = new Random();

// 设定背景色

img.setColor(getRandColor(COLOR_FC_BG, COLOR_BC_BG));

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

// 设定字体

img.setFont(new Font("Times New Roman", Font.PLAIN, 18));

// 画边框

// g.setColor(new Color());

// g.drawRect(0,0,width-1,height-1);

// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到

img.setColor(getRandColor(COLOR_FC_LINE, COLOR_BC_LINE));

for (int i = 0; i < 155; i++) {

int x = random.nextInt(WIDTH);

int y = random.nextInt(HEIGHT);

int xl = random.nextInt(12);

int yl = random.nextInt(12);

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

}

// 取随机产生的认证码(4位数字)

String codeValue = "";

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

//String rand = String.valueOf(random.nextInt(10));

String rand = getRandomChar();

codeValue = codeValue.concat(rand);

img.setFont(getRandomFont());//随机字体

// 将认证码显示到图象中

img.setColor(getRandColor(COLOR_FC_CODE, COLOR_BC_CODE));

img.drawString(rand, 13 * i + 6, 16);

}

request.getSession().setAttribute("codeValue", codeValue);

// 图象生效

img.dispose();

// 输出图象到页面

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

}

/**

* 随机生成字符，含大写、小写、数字

* function: 功能

* @createDate 2010-8-23 上午10:33:55

* @author hoojo

* @return

public static String getRandomChar() {

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

String randChar = "";

switch (index) {

case 0://大写字符

randChar = String.valueOf((char)Math.round(Math.random() * 25 + 65));

break;

case 1://小写字符

randChar = String.valueOf((char)Math.round(Math.random() * 25 + 97));

break;

default://数字

randChar = String.valueOf(Math.round(Math.random() * 9));

break;

}

return randChar;

}

/**

* function: 随机生成字体、文字大小

* @createDate 2010-8-23 上午10:44:22

* @author hoojo

* @return

public static Font getRandomFont() {

String[] fonts = {"Georgia", "Verdana", "Arial", "Tahoma", "Time News Roman", "Courier New", "Arial Black", "Quantzite"};

int fontIndex = (int)Math.round(Math.random() * (fonts.length - 1));

int fontSize = (int) Math.round(Math.random() * 4 + 16);

return new Font(fonts[fontIndex], Font.PLAIN, fontSize);

}

其中验证码的值是保存在session中：request.getSession().setAttribute("codeValue", codeValue);

比较用户输入的值和session中的codeValue是否相等即可；

下面是jsp页面调用servlet：ValidCodeServlet.java

ValidCodeServlet中调用了上面的ValidCodeUtils 验证码生成工具类

package com.hoo.servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.hoo.util.ValidCodeUtils;

@SuppressWarnings("serial")

public class ValidCodeServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

try {

ValidCodeUtils.getImage(request, response);

} catch (Exception e) {

e.printStackTrace();

}

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

doGet(request, response);

}

jsp页面调用servlet方法即可

js：reloadValidCode方法

function reloadValidCode(o) {

o.src = "${pageContext.request.contextPath }/validCodeServlet?timed=" + new Date().getMilliseconds();

}

这里的"timed=" + new Date().getMilliseconds();是需要防止IE缓存用的

html标签：

直接跟Servlet名称配置的url即可，和web.xml配置对应。主要调用路径${pageContext.request.contextPath }/validCodeServlet这样会带上根目录，比较保险。

web.xml中validCodeServlet配置

<servlet-name>validCodeServlet</servlet-name>

<servlet-class>com.hoo.servlet.ValidCodeServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>validCodeServlet</servlet-name>

<url-pattern>/validCodeServlet</url-pattern>

</servlet-mapping>