Java web 开发： 随机生成验证码，支持大小写字母、数字；随机字体

java随机产生验证码，可以随机生成数字、大写字母、小写字母。还可以随机生成文字字体、及大小。在图片上面可能字体都不不同、大小不等。 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>

至此，整个图片验证码就配置完毕。在浏览器中输入你请求的url，在jsp页面中就可以看到效果

怎样，效果还很理想吧。字体、大小、数字、大小写字符、及颜色等！