登录时生成验证码和后台验证详解（验证码图片用jsp显示出来的）

登录窗口代码HTML

			    

				

					
员工登录
					

						

							账号
							

								
							
						
						

							密码
							

								
							
						
						

							验证码
							

								
							
							

								
							
						
						

							
							

								　记住用户名
							
							

								忘记密码
							
						
						

							立即登录
							
						
					
				
			
		

validatecode.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page import="java.util.Random"%>
<%@ page import="java.io.OutputStream"%>
<%@ page import="java.awt.Color"%>
<%@ page import="java.awt.Font"%>
<%@ page import="java.awt.Graphics"%>
<%@ page import="java.awt.image.BufferedImage"%>
<%@ page import="javax.imageio.ImageIO"%>
<%
	int width = 100;
	int height = 32;
	//create the image
	BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
	Graphics g = image.getGraphics();
	// set the background color
	g.setColor(new Color(0xDCDCDC));
	g.fillRect(0, 0, width, height);
	// draw the border
	g.setColor(Color.black);
	g.drawRect(0, 0, width - 1, height - 1);
	// create a random instance to generate the codes
	Random rdm = new Random();
	String hash1 = Integer.toHexString(rdm.nextInt());
	// make some confusion
	for (int i = 0; i < 50; i++) {
		int x = rdm.nextInt(width);
		int y = rdm.nextInt(height);
		g.drawOval(x, y, 0, 0);
	}
	// generate a random code
	String capstr = hash1.substring(0, 4);
	session.setAttribute("key", capstr);//将验证码存储到session中
	g.setColor(new Color(0, 100, 0));
	g.setFont(new Font("Candara", Font.BOLD, 24));
	g.drawString(capstr, 8, 24);
	g.dispose();
	response.setContentType("image/jpeg");
	out.clear();
	out = pageContext.pushBody();
	OutputStream strm = response.getOutputStream();
	ImageIO.write(image, "jpeg", strm);
	strm.close();
%>

后台对验证码的验证

// 判断验证码 是否正确
        String key = (String) ServletActionContext.getRequest().getSession().getAttribute("key");// session中验证码
        if (key == null || !key.equals(ServletActionContext.getRequest().getParameter("checkcode"))) {
            // 验证码无效
            ServletActionContext.getRequest().setAttribute("msg", "验证码错误");
            return "input";
        }