生成校验码

checkcode.jsp

<%@ page contentType="image/jpeg"
	import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"%>
<%!Color getRandColor(int fc, int bc) {
		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();//这句针对resin服务器，如果是tomacat可以不要这句
	response.setHeader("Pragma", "No-cache");
	response.setHeader("Cache-Control", "no-cache");
	response.setDateHeader("Expires", 0);

	int width = 60, height = 20;
	BufferedImage image = new BufferedImage(width, height,
			BufferedImage.TYPE_INT_RGB);

	Graphics g = image.getGraphics();
	Random random = new Random();

	g.setColor(getRandColor(200, 250));
	g.fillRect(0, 0, width, height);

	g.setFont(new Font("Times New Roman", Font.PLAIN, 18));

	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);
	}

	String sRand = "";
	for (int i = 0; i < 4; i++) {
		String rand = String.valueOf(random.nextInt(10));
		sRand += rand;

		g.setColor(new Color(20 + random.nextInt(110), 20 + random
				.nextInt(110), 20 + random.nextInt(110)));
		g.drawString(rand, 13 * i + 6, 16);
	}

	//将认证码存入SESSION
	session.setAttribute("checkcode", sRand);
	g.dispose();

	ImageIO.write(image, "JPEG", response.getOutputStream());
	response.getOutputStream().close();
	out.clear();
	out = pageContext.pushBody();
%>

    login.jsp

    

<div class="code">&nbsp;验证码：<span><input  maxlength="20" size="13" name="checkcode"  class="code_input" id="checkcode"  onKeyUp="this.value=this.value.replace(/\D*(\d*\.?\d{0,2})\d*\D*/g,'$1')"></span>
							   <span><a href="#">
							   <img src="${ctx}/common/checkcode.jsp" width="60" height="20" border="0" class="code_img" id="checkcode_img" onclick="refreshCode();" /></a></span>
						   </div>

    javascript:

   

function refreshCode(){
		$("#checkcode_img").attr("src","${ctx}/common/checkcode.jsp?random="+Math.random());
	}