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<%@ page language="java" pageEncoding="utf-8" %>
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<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %><%@ page session="true" %><%
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// 在内存中创建图象
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int width=60, height=20;
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BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
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// 获取图形上下文
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Graphics g = image.getGraphics();
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// 设定背景色
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g.setColor(Color.white);
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g.fillRect(0, 0, width, height);
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//画边框
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g.setColor(Color.black);
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g.drawRect(0,0,width-1,height-1);
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// 取随机产生的认证码(4位数字)
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String rand = Math.random()*10000+"";
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rand = rand.substring(0,rand.indexOf("."));
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switch(rand.length())
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{
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case 1: rand = "000"+rand; break;
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case 2: rand = "00"+rand; break;
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case 3: rand = "0"+rand; break;
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default: rand = rand.substring(0,4); break;
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}
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// 将认证码显示到图象中
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g.setColor(Color.black);
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g.setFont(new Font("Fixedsys",Font.BOLD,18));
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g.drawString(rand,10,16);
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// 随机产生88个干扰点，使图象中的认证码不易被其它程序探测到
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Random random=new Random();
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for (int i=0;i<88;i++)
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{
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int x = random.nextInt(width);
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int y = random.nextInt(height);
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g.drawLine(x,y,x,y);
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}
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// 图象生效
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g.dispose();
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// 将认证码存入SESSION
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HttpSession sessionLogin=request.getSession(true);
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sessionLogin.setAttribute("randKey",rand);
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// System.out.println("rand:"+rand);
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// 输出图象到页面
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//<IMG src="num.jsp" WIDTH=60 HEIGHT=20 >
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ImageIO.write(image, "JPEG", response.getOutputStream());
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%>
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