一次验证

package web1;

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;

public class ValidateColorServlet extends HttpServlet {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	public static final String CHECK_CODE_KEY = "CHECK_CODE_KEY";


	// 设置验证图片的宽度, 高度, 验证码的个数
	private int width = 152;
	private int height = 40;
	private int codeCount = 6;

	// 验证码字体的高度
	private int fontHeight = 4;

	// 验证码中的单个字符基线. 即：验证码中的单个字符位于验证码图形左上角的 (codeX, codeY) 位置处
	private int codeX = 0;
	private int codeY = 0;

	// 验证码由哪些字符组成
	char[] codeSequence = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz23456789".toCharArray();

	// 初始化验证码图形属性
	public void init() {
		fontHeight = height - 2;
		codeX = width / (codeCount + 2);
		codeY = height - 4;
	}

	public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// 定义一个类型为 BufferedImage.TYPE_INT_BGR 类型的图像缓存
		BufferedImage buffImg = null;
		buffImg = new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);

		// 在 buffImg 中创建一个 Graphics2D 图像
		Graphics2D graphics = null;
		graphics = buffImg.createGraphics();

		// 设置一个颜色, 使 Graphics2D 对象的后续图形使用这个颜色
		graphics.setColor(Color.WHITE);

		// 填充一个指定的矩形: x - 要填充矩形的 x 坐标; y - 要填充矩形的 y 坐标; width - 要填充矩形的宽度; height
		// - 要填充矩形的高度
		graphics.fillRect(0, 0, width, height);

		// 创建一个 Font 对象: name - 字体名称; style - Font 的样式常量; size - Font 的点大小
		Font font = null;
		font = new Font("", Font.BOLD, fontHeight);
		// 使 Graphics2D 对象的后续图形使用此字体
		graphics.setFont(font);

		graphics.setColor(Color.BLACK);

		// 绘制指定矩形的边框, 绘制出的矩形将比构件宽一个也高一个像素
		graphics.drawRect(0, 0, width - 1, height - 1);

		// 随机产生 15 条干扰线, 使图像中的认证码不易被其它程序探测到
		Random random = null;
		random = new Random();
		graphics.setColor(Color.GREEN);
		for (int i = 0; i < 55; i++) {
			int x = random.nextInt(width);
			int y = random.nextInt(height);
			int x1 = random.nextInt(20);
			int y1 = random.nextInt(20);
			graphics.drawLine(x, y, x + x1, y + y1);
		}

		// 创建 randomCode 对象, 用于保存随机产生的验证码, 以便用户登录后进行验证
		StringBuffer randomCode;
		randomCode = new StringBuffer();

		for (int i = 0; i < codeCount; i++) {
			// 得到随机产生的验证码数字
			String strRand = null;
			strRand = String.valueOf(codeSequence[random.nextInt(36)]);

			// 把正在产生的随机字符放入到 StringBuffer 中
			randomCode.append(strRand);

			// 用随机产生的颜色将验证码绘制到图像中
			graphics.setColor(Color.BLUE);
			graphics.drawString(strRand, (i + 1) * codeX, codeY);
		}

		// 再把存放有所有随机字符的 StringBuffer 对应的字符串放入到 HttpSession 中
		request.getSession().setAttribute(CHECK_CODE_KEY, randomCode.toString());

		// 禁止图像缓存
		response.setHeader("Pragma", "no-cache");
		response.setHeader("Cache-Control", "no-cache");
		response.setDateHeader("Expires", 0);

		// 将图像输出到输出流中
		ServletOutputStream sos = null;
		sos = response.getOutputStream();
		ImageIO.write(buffImg, "jpeg", sos);
		sos.close();
	}

}

package web1;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class CheckCodeServlet
 */
@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
      //1 获取请求参数  CHECK_CODE_PARAM_NAME
		String  name=request.getParameter("CHECK_CODE_PARAM_NAME");
		//2 获取session中的CHECK_CODE_KEY属性值
		String  sessionCode=(String) request.getSession().getAttribute("CHECK_CODE_KEY");
		System.out.println(name);
		System.out.println(sessionCode);
		//3  对比  看是否一致  若一致说明  验证码正确  若不一致 说明验证码错误
		if(!(name!=null&&name.equals(sessionCode))){
			request.getSession().setAttribute("message", "验证码不一致");
		   response.sendRedirect(request.getContextPath()+"/check/index.jsp");
		return;
		}
		System.out.println("受理请求！");

//		//1.获取请求信参数  CHECK_CODE_PARAM_NAME
//		String   paramname=request.getParameter("CHECK_CODE_PARMA_NAME");
//		//  2.获取session中的CHECK_CODE_KEY值
//		String  key=(String) request.getSession().getAttribute("CHECK_CODE_KEY");
//		System.out.println(paramname);
//		System.out.println(key);
//		//3，对比看看  是否一致   若izhi说明验证码通过  不一致验证吗错误
//		if(!(paramname!=null&&paramname.equals(key))){
//			request.setAttribute("message", "验证码错误！");
//			response.sendRedirect(request.getContextPath()+"/check/check.jsp");
//		return;
//		}
//		System.out.println("受理请求！！");
		
	}

}

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
     <font  color="red">
               <%=session.getAttribute("message")==null ? "":session.getAttribute("message") %>
    
    </font>
      <form action="<%= request.getContextPath()%>/checkCodeServlet"   method="post">
      name:<input type="text" name="name"/>
      checkCode:<input type="text" name="CHECK_CODE_PARAM_NAME"/>
      <img alt="" src="<%=request.getContextPath()%>/validateColorServlet"/>
        <input type="submit" value="Submit"/>
      </form>
      
   <%-- 
   
   <font color="red">
         <%=session.getAttribute("message")==null ? "":session.getAttribute("message") %>
      
      </font>
      <form action="<%=request.getContextPath()%>/checkcodeServlet" method="post">
       name:<input type="text" name="name"/>      
       checkCode=：<input type="text" name="CHECK_CODE_PARAM_NAME"/>
       <img alt="" src="<%=request.getContextPath()%>/validateColorServlet">
       <input type="submit" value="Submit"/>
      </form>
   --%>   
      
      
      
</body>
</html>

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
        <h4>Success  Page</h4>
</body>
</html>

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
   <h4>对不起，已经提交过了</h4>
</body>
</html>

在web.xml中配置Servlet

<servlet>
    <servlet-name>validateColorServlet1</servlet-name>
    <servlet-class>web1.ValidateColorServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
     <servlet-name>validateColorServlet1</servlet-name>
     <url-pattern>/validateColorServlet</url-pattern>
  </servlet-mapping>