转载自 java生成验证码
源码：
package seed.lee.image;import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
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 ImageServlet extends HttpServlet {private int imgWidth = 0;private int imgHeight = 0;private int codeCount = 0;private int x = 0;private int fontHeight;private int codeY;private String fontStyle;private static final long serialVersionUID = 128554012633034503L;/*** 初始化配置参数*/public void init() throws ServletException {// 从web.xml中获取初始信息// 宽度String strWidth = this.getInitParameter("imgWidth");// 高度String strHeight = this.getInitParameter("imgHeight");// 字符个数String strCodeCount = this.getInitParameter("codeCount");fontStyle = this.getInitParameter("fontStyle");// 将配置的信息转换成数值try {if (strWidth != null && strWidth.length() != 0) {imgWidth = Integer.parseInt(strWidth);}if (strHeight != null && strHeight.length() != 0) {imgHeight = Integer.parseInt(strHeight);}if (strCodeCount != null && strCodeCount.length() != 0) {codeCount = Integer.parseInt(strCodeCount);}} catch (NumberFormatException e) {e.printStackTrace();}x = imgWidth / (codeCount + 1);fontHeight = imgHeight - 2;codeY = imgHeight - 12;}/*** * @param request* @param response* @throws ServletException* @throws IOException*/protected void processRequest(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {response.setContentType("image/jpeg");response.setHeader("Pragma", "No-cache");response.setHeader("Cache-Control", "no-cache");response.setDateHeader("Expires", 0);HttpSession session = request.getSession();// 在内存中创建图象BufferedImage image = new BufferedImage(imgWidth, imgHeight,BufferedImage.TYPE_INT_RGB);// 获取图形上下文Graphics2D g = image.createGraphics();// 生成随机类Random random = new Random();// 设定背景色g.setColor(Color.WHITE);g.fillRect(0, 0, imgWidth, imgHeight);// 设定字体g.setFont(new Font(fontStyle, Font.PLAIN + Font.ITALIC, fontHeight));// 画边框g.setColor(new Color(55, 55, 12));g.drawRect(0, 0, imgWidth - 1, imgHeight - 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g.setColor(getRandColor(160, 200));for (int i = 0; i < 160; i++) {int x = random.nextInt(imgWidth);int y = random.nextInt(imgHeight);int xl = random.nextInt(12);int yl = random.nextInt(12);g.drawLine(x, y, x + xl, y + yl);}// 取随机产生的认证码(4位数字)String sRand = "";int red = 0, green = 0, blue = 0;for (int i = 0; i < codeCount; i++) {red = random.nextInt(255);green = random.nextInt(255);blue = random.nextInt(255);int wordType = random.nextInt(3);char retWord = 0;switch (wordType) {case 0:retWord = this.getSingleNumberChar();break;case 1:retWord = this.getLowerOrUpperChar(0);break;case 2:retWord = this.getLowerOrUpperChar(1);break;}sRand += String.valueOf(retWord);g.setColor(new Color(red, green, blue));g.drawString(String.valueOf(retWord), (i) * x, codeY);}// 将认证码存入SESSIONsession.setAttribute("rand", sRand);// 图象生效g.dispose();ServletOutputStream responseOutputStream = response.getOutputStream();// 输出图象到页面ImageIO.write(image, "JPEG", responseOutputStream);// 以下关闭输入流！responseOutputStream.flush();responseOutputStream.close();}Color getRandColor(int fc, int bc) {// 给定范围获得随机颜色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);}protected void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {processRequest(request, response);}protected void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {processRequest(request, response);}private char getSingleNumberChar() {Random random = new Random();int numberResult = random.nextInt(10);int ret = numberResult + 48;return (char) ret;}private char getLowerOrUpperChar(int upper) {Random random = new Random();int numberResult = random.nextInt(26);int ret = 0;if (upper == 0) {// 小写ret = numberResult + 97;} else if (upper == 1) {// 大写ret = numberResult + 65;}return (char) ret;}}配置（web.xml）：
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"><servlet><servlet-name>imageServlet</servlet-name><servlet-class>seed.lee.image.ImageServlet</servlet-class><init-param><!-- 图宽 --><param-name>imgWidth</param-name><param-value>200</param-value></init-param><init-param><!-- 图高 --><param-name>imgHeight</param-name><param-value>80</param-value></init-param><init-param><!-- 显示的字符数 --><param-name>codeCount</param-name><param-value>5</param-value></init-param><init-param><!-- 字体类型 --><param-name>fontStyle</param-name><param-value>Times New Roman</param-value></init-param></servlet><servlet-mapping><servlet-name>imageServlet</servlet-name><url-pattern>/imageServlet</url-pattern></servlet-mapping><welcome-file-list><welcome-file>index.jsp</welcome-file></welcome-file-list>
</web-app>
下载源码：http://u.115.com/file/dnacj1en
)
