javaweb之驗證碼驗證技術

今天學習了一個驗證碼校驗技術，所以就寫下了一些筆記，方便日后查看。首先創建web工程

1、然后在src目錄下創建一個Servlet類，此類用來顯示登錄頁面和錯誤信息提示

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();
        
        //返回一個界面
        
        out.println("<h1>用戶登錄</h1>");
        out.println("<form action='/CheckCode/LoginCl' method='get'>");
        out.println("用戶名：<input type='text' name='id'><br>");
        out.println("密碼：<input type='password' name='password'><br>");
        out.println("驗證碼:<input type='text' name='checkcode'><img src='/CheckCode/CreateCode'><br>");//加載驗證碼圖片是只要將產生驗證碼的對應類路徑指定到img標簽中即可 42         out.println("<input type='submit' value='登錄'><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、繼續創建一個Servlet,用來顯示校驗成功后的頁面。

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();
        
        //獲取用戶的id/password/輸入驗證碼
        String id = request.getParameter("id");
        String passwd = request.getParameter("password");
        String checkCode = request.getParameter("checkcode");
        //取出session中驗證碼
        String checkcode2 = (String) request.getSession().getAttribute("checkcode");
                
        //1.先驗證碼
        if(checkCode.equals(checkcode2)) {
            //驗證碼ok
            request.getRequestDispatcher("/OK").forward(request, response);
            //到數據庫去驗證
        }else {
            request.setAttribute("err", "驗證碼錯誤");
            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、最后創建驗證碼產生的Servlet，用來產生隨機數校驗碼圖片，並將該驗證碼圖片返回到客戶端。此類比較關鍵。

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 {
        
        //禁止瀏覽器緩沖隨機圖片
        response.setDateHeader("Expires", -1);//防止啟動瀏覽器時取先前緩沖的數據
        response.setHeader("Cache-Control", "no-cache");
        response.setHeader("Pragma", "no-cache");
        
        //通知客戶機以圖片方式打開發送過去的數據
        response.setHeader("Content-Type", "image/jpeg");
        
        //在內存中創建一副圖片
        BufferedImage image = new BufferedImage(80, 30, BufferedImage.TYPE_INT_BGR);
        
        //想圖片上寫數據
        Graphics graphics = image.getGraphics();
        
        //設置背景色
        graphics.setColor(Color.WHITE);
        graphics.fillRect(0, 0, 80, 30);
        
        //設置寫入數據的顏色和字體
        graphics.setColor(Color.BLACK);
        graphics.setFont(new Font(null, Font.BOLD, 20));
        
        //像圖片上寫數據
        String num = makeNum();
        
        //把隨機生成的數值，保存到session中
        request.getSession().setAttribute("checkcode", num);
        graphics.drawString(num, 0, 20);
        
        //把寫好數據的圖片輸出給瀏覽器
        ImageIO.write(image, "jpg", response.getOutputStream());
        
        
    }

    /**
     * 功能：隨機生成7位數字
     * @return
     */
    private String makeNum() {
        Random random = new Random();
        //9999999可以生成7位數
        String num = random.nextInt(9999999)+"";
        StringBuffer stringBuffer = new StringBuffer();
        //如果不夠指定位數則補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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