本文实例为大家分享了Java随机生成验证码的具体代码，供大家参考，具体内容如下
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 RandImage extends HttpServlet {/*** Constructor of the object.*/ public RandImage() { super(); } private int imgWidth = 0; //图片宽度 private int imgHeight = 0; //图片的高度 private int codeCount = 0; //图片里面字符的个数 private int x = 0; private int fontHeight; //字体的高度 private int codeY; private String fontStyle; //字体样式 //序列化ID 避免重复 private static final long serialVersionUID = 128554012633034503L; /** * 初始化配置参数 */public void init() throws ServletException { // 宽度 String strWidth = "200"; // 高度 String strHeight ="80"; // 字符个数 String strCodeCount ="5"; //字体 fontStyle = "Times New Roman";// 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); //字符间距 fontHeight = imgHeight - 2; //字体的高度 codeY = imgHeight - 12; // 代码高度 } protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //输出流设置 response.setContentType("image/jpeg"); //输出格式 response.setHeader("Pragma", "No-cache");//不缓存 重新生成 response.setHeader("Cache-Control", "no-cache");//不缓存 重新生成 response.setDateHeader("Expires", 0); //0秒失效 也是不缓存 HttpSession session = request.getSession(); //获取session 会话 // 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(); //随机类 // 设定矩形的背景色 g.setColor(Color.WHITE); //填充矩形Rect为白色 g.fillRect(0, 0, imgWidth, imgHeight); // 设定边框字体 g.setFont(new Font(fontStyle, Font.PLAIN + Font.ITALIC, fontHeight)); //设置边框的颜色 g.setColor(new Color(55, 55, 12)); // 画边框 g.drawRect(0, 0, imgWidth - 1, imgHeight - 1); // 随机产生160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++) { //循环生成codeCount个随机字符 //通过rgb三色随机得到新的颜色 red = random.nextInt(255); green = random.nextInt(255); blue = random.nextInt(255); //随机得到一个0 1 2 的数字 int wordType = random.nextInt(3);//随机得到0-2之间的3个数字 char retWord = 0; //0 数字 1 小写字母 2 大写字母 switch (wordType) { case 0: retWord = this.getSingleNumberChar(); //得到0-9的char型数字 break; case 1: retWord = this.getLowerOrUpperChar(0); //得到小写的char型字母 break; case 2: retWord = this.getLowerOrUpperChar(1); //得到大写的char型字母 break; } sRand += String.valueOf(retWord); //将得到的随机字符 连接起来 g.setColor(new Color(red, green, blue)); //设置一个颜色 g.drawString(String.valueOf(retWord), 2+(i) * x, codeY); //将字符写到图片中 对应的位置 } // 将认证码存入SESSION session.setAttribute("rand", sRand); //将得到的随机字符存入到session回话中，验证的时候可以调用 // 图象生效 g.dispose(); //释放g 对象 ServletOutputStream responseOutputStream = response.getOutputStream(); //输出流 // 输出图象到页面 ImageIO.write(image, "JPEG", responseOutputStream); //以JPEG的格式输出 // 以下关闭输入流！ responseOutputStream.flush();//刷新并关闭流 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); } // 将整型随机数字转换成char返回 private char getSingleNumberChar() { Random random = new Random(); int numberResult = random.nextInt(10); int ret = numberResult + 48; //将字符 '0‘ 转换成ascall码的时候 就是48 return (char) ret; } //得到26个字符 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; }}以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持武林网。