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：

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;
 /**
 * <b>function:</b> 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);
 }

/**
  * <b>function:</b> 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
  * <b>function:</b> 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;
 }

 /**
  * <b>function:</b> 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：
 <img src="${pagecontext.request.contextpath }/validcodeservlet" title="看不清，点击刷新" onclick="reloadvalidcode(this)"/>
 直接跟servlet名称配置的url即可，和web.xml配置对应。主要调用路径${pagecontext.request.contextpath }/validcodeservlet这样会带上根目录，比较保险。

web.xml中validcodeservlet配置
 <servlet>
 <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>