javaweb之验证码验证技术

今天学习了一个验证码校验技术，所以就写下了一些笔记，方便日后查看。首先创建web工程

1、然后在src目录下创建一个Servlet类，此类用来显示登录页面和错误信息提示

 package com.LHB;

 import java.io.IOException;
 import java.io.PrintWriter;

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

     /**
      * @see HttpServlet#HttpServlet()
      */
     public Login() {
         super();
         // TODO Auto-generated constructor stub
     }

     /**
      * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
      */
     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

         response.setContentType("text/html;charset=utf-8");
         PrintWriter out = response.getWriter();

         //返回一个界面

         out.println("<h1>用户登录</h1>");
         out.println("<form action='/CheckCode/LoginCl' method='get'>");
         out.println("用户名：<input type='text' name='id'><br>");
         out.println("密码：<input type='password' name='password'><br>");
         out.println("验证码:<input type='text' name='checkcode'><img src='/CheckCode/CreateCode'><br>");//加载验证码图片是只要将产生验证码的对应类路径指定到img标签中即可
         out.println("<input type='submit' value='登录'><br>");

         out.println("</form>");
         String err=(String) request.getAttribute("err");
         if(err!=null) {
             out.println(err);
         }
     }

     /**
      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
      */
     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         // TODO Auto-generated method stub
         doGet(request, response);
     }

 }

2、继续创建一个Servlet,用来显示校验成功后的页面。

 package com.LHB;

 import java.io.IOException;
 import java.io.PrintWriter;

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

     /**
      * @see HttpServlet#HttpServlet()
      */
     public LoginCl() {
         super();
         // TODO Auto-generated constructor stub
     }

     /**
      * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
      */
     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

         response.setContentType("text/html;charset=utf-8");
         PrintWriter out = response.getWriter();

         //获取用户的id/password/输入验证码
         String id = request.getParameter("id");
         String passwd = request.getParameter("password");
         String checkCode = request.getParameter("checkcode");
         //取出session中验证码
         String checkcode2 = (String) request.getSession().getAttribute("checkcode");

         //1.先验证码
         if(checkCode.equals(checkcode2)) {
             //验证码ok
             request.getRequestDispatcher("/OK").forward(request, response);
             //到数据库去验证
         }else {
             request.setAttribute("err", "验证码错误");
             request.getRequestDispatcher("/Login").forward(request, response);
         }

     }

     /**
      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
      */
     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         // TODO Auto-generated method stub
         doGet(request, response);
     }

 }

3、最后创建验证码产生的Servlet，用来产生随机数校验码图片，并将该验证码图片返回到客户端。此类比较关键。

 package com.LHB;

 import java.awt.Color;
 import java.awt.Font;
 import java.awt.Graphics;
 import java.awt.image.BufferedImage;
 import java.io.IOException;
 import java.util.Random;

 import javax.imageio.ImageIO;
 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 CreateCode
  */
 @WebServlet("/CreateCode")
 public class CreateCode extends HttpServlet {
     private static final long serialVersionUID = 1L;

     /**
      * @see HttpServlet#HttpServlet()
      */
     public CreateCode() {
         super();
         // TODO Auto-generated constructor stub
     }

     /**
      * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
      */
     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

         //禁止浏览器缓冲随机图片
         response.setDateHeader("Expires", -1);//防止启动浏览器时取先前缓冲的数据
         response.setHeader("Cache-Control", "no-cache");
         response.setHeader("Pragma", "no-cache");

         //通知客户机以图片方式打开发送过去的数据
         response.setHeader("Content-Type", "image/jpeg");

         //在内存中创建一副图片
         BufferedImage image = new BufferedImage(80, 30, BufferedImage.TYPE_INT_BGR);

         //想图片上写数据
         Graphics graphics = image.getGraphics();

         //设置背景色
         graphics.setColor(Color.WHITE);
         graphics.fillRect(0, 0, 80, 30);

         //设置写入数据的颜色和字体
         graphics.setColor(Color.BLACK);
         graphics.setFont(new Font(null, Font.BOLD, 20));

         //像图片上写数据
         String num = makeNum();

         //把随机生成的数值，保存到session中
         request.getSession().setAttribute("checkcode", num);
         graphics.drawString(num, 0, 20);

         //把写好数据的图片输出给浏览器
         ImageIO.write(image, "jpg", response.getOutputStream());

     }

     /**
      * 功能：随机生成7位数字
      * @return
      */
     private String makeNum() {
         Random random = new Random();
         //9999999可以生成7位数
         String num = random.nextInt(9999999)+"";
         StringBuffer stringBuffer = new StringBuffer();
         //如果不够指定位数则补0
         for(int i=0;i<7-num.length();i++) {
             stringBuffer.append("0");
         }
         num = stringBuffer.toString() + num;
         return num;
     }

     /**
      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
      */
     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         // TODO Auto-generated method stub
         doGet(request, response);
     }

 }

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