JSP頁面生成随機驗證碼

1、 随機生成的數字驗證碼

image.jsp：

<%@ page import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"%>
<%@ page import="java.io.OutputStream"%>

<%!
   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);
   }
%>
<%
   try {
      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);
      OutputStream os = response.getOutputStream();
      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 +4, 16);
      }

     
      //把生成的驗證碼放入session中，以便後面驗證時使用
      session.setAttribute("rand", sRand);
      g.dispose();

      ImageIO.write(image, "JPEG", os);
      os.flush();
      os.close();
      os = null;
      response.flushBuffer();
      out.clear();
      out = pageContext.pushBody();
   } catch (IllegalStateException e) {
      System.out.println(e.getMessage());
      e.printStackTrace();
   }
%>
           

2.   随即生成的字母和數字的驗證碼

enimg.jsp:

<%@ page import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"%>
<%@ page import="java.io.OutputStream"%>
<%!
   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);
   }
%>

<%
   try {
      response.setHeader("Pragma", "No-cache");
      response.setHeader("Cache-Control", "no-cache");
      response.setDateHeader("Expires", 0);

      int width = 110, height = 20;
      BufferedImage image = new BufferedImage(width, height,
           BufferedImage.TYPE_INT_RGB);
      OutputStream os = response.getOutputStream();

      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[] s = { "A", "B", "C", "D", "E", "F", "G", "H", "I",

           "J", "K", "L", "M", "N", "P", "Q", "R", "S", "T", "U",

           "V", "W", "X", "Y", "Z" };
      String sRand = "";

      for (int i = 0; i < 4; i++) {
        String rand = "";
        if (random.nextBoolean()) {
           rand = String.valueOf(random.nextInt(10));
        } else {
           int index = random.nextInt(25);
           rand = s[index];
        }

        sRand += rand;
        g.setColor(new Color(20 + random.nextInt(10), 20 + random
              .nextInt(110), 20 + random.nextInt(110)));
        g.drawString(rand, 17 * i + 6, 16);
      }

      //把生成的驗證碼放入session中，以便後面驗證時使用
      session.setAttribute("rand", sRand);
      g.dispose();

      ImageIO.write(image, "JPEG", os);

      os.flush();
      os.close();
      os = null;
      response.flushBuffer();
      out.clear();
      out = pageContext.pushBody();
   } catch (IllegalStateException e) {
      System.out.println(e.getMessage());
      e.printStackTrace();
   }
%>
           

3.使用

authcode.jsp：

<%@ 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>

   <!-- 點選“看不清點我”，觸發onclick事件，會調用該方法 -->
   <script language="javascript">
      function loadimage(){
        document.getElementByIdx_x("randImage").src = "image.jsp?" + Math.random(); //後跟一個随機數，否則驗證碼不會變
      }
   </script>

<body>

   <h1>登陸</h1>
   <hr>
  

   <form action="AuthcodeServlet" method="post">

      username:<input type="text" name="username" /><br>
      password:<input type="text" name="password" /><br>
      authcode:<input type="text" name="rand" /><br>


      <!-- 顯示驗證碼圖檔，第一次進入頁面，驗證碼有這裡顯示 -->
      <img alt="code..." name="randImage" id="randImage" src="image.jsp"
                 width="60" height="20"  align="absmiddle">&nbsp;&nbsp;
      <!-- 更改驗證碼 -->
      <a href="javascript:loadimage();" target="_blank" rel="external nofollow" ><font class="pt95">看不清點我</font></a><br>

      <input type="submit" value="login" />

   </form>
</body>
</html>