<%@page import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*, sun.misc.BASE64Encoder, java.awt.image.DataBufferByte, java.io.*,javax.swing.ImageIcon"%>//tomcat下 <%@ page contentType="image/jpg"  language="java"%>//resin下<%@ page contentType="text/html"  language="java"%><%!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);}%><%out.clear();//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int width=60, height=30;BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);// 获取图形上下文Graphics g = image.getGraphics();//生成随机类Random random = new Random();// 设定背景色g.setColor(getRandColor(200,250)); g.fillRect(0, 0, width, height);//设定字体g.setFont(new Font("Times New Roman",Font.PLAIN, 32));//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g.setColor(getRandColor(160,200));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);        g.drawLine(x,y,x+xl,y+yl);}// 取随机产生的认证码(4位数字)/*for(int i=0; i < sRand.length(); i++) {    String rand=String.valueOf(sRand.charAt(i));    // 将认证码显示到图象中    g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成    g.drawString(rand, 13*i + 6, 16);}*/String sRand = "";for (int i=0;i<4;i++){    String rand=String.valueOf(random.nextInt(10));    sRand+=rand;    // 将认证码显示到图象中    g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成    g.drawString(rand, 13*i+2, 24);}// 将认证码存入SESSIONsession.setAttribute("validateCode", sRand);// 图象生效g.dispose();// tomcat下使用下方法输出图象到页面//ImageIO.write(image, "JPG", response.getOutputStream());//resin 下base64解决办法ByteArrayOutputStream byteOut = new ByteArrayOutputStream(); try {    ImageIO.write(image, "JPEG", byteOut);        byte[] data =http://www.mamicode.com/ byteOut.toByteArray();         BASE64Encoder encoder = new BASE64Encoder();    out.write(encoder.encode(data));    out.flush();    out.clear();} catch (IOException e) {     e.printStackTrace();}%>