package com.xia;

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.servlet.ServletOutputStream;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.sun.image.codec.jpeg.JPEGCodec;

import com.sun.image.codec.jpeg.JPEGImageEncoder;

/**

* @(#)VerifyCodeServlet.java Dec 9, 2007 8:14:14 PM

*

* @author Yuan

* 驗證碼生成器，使用此類需要將表單里的驗證碼輸入框的name屬性設為"verifycode"

*/

public class VerifyCodeGenerator {

    public static final VerifyCodeGenerator generator = new VerifyCodeGenerator();

    private final String ATTRIBUTE_NAME = "verifycode";

    //圖片的寬度

    private final int WIDTH = 15;

    //圖片的高度

    private final int HEIGHT = 22;

    //字符串長度

    private final int CODE_LENGTH = 4;

    //隨機字符串范圍

    private final String RAND_RANGE = "abcdefghijklmnopqrstuvwxyz"

        + "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

        + "1234567890" ;

    private final char[] CHARS = RAND_RANGE.toCharArray();

    private Random random = new Random();

    public VerifyCodeGenerator(){

        //

    }

    public static VerifyCodeGenerator getInstance(){

        return generator;

    }

    /**

     * 生成隨機字符串

     * @return 隨機字符串

     */

    private String getRandString(){

        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < CODE_LENGTH; i++)

            sb.append(CHARS[random.nextInt(CHARS.length)]);

        return sb.toString();

    }

    /**

     * 生成隨機顏色

     * @param ll 產生顏色值下限(lower limit)

     * @param ul 產生顏色值上限(upper limit)

     * @return 生成的隨機顏色對象

     */

    private Color getRandColor(int ll, int ul){

        if (ll > 255) ll = 255;

        if (ll < 1) ll = 1;

        if (ul > 255) ul = 255;

        if (ul < 1) ul = 1;

        if (ul == ll) ul = ll + 1;

        int r = random.nextInt(ul - ll) + ll;

        int g = random.nextInt(ul - ll) + ll;

        int b = random.nextInt(ul - ll) + ll;

        Color color = new Color(r,g,b);

        return color;

    }

    /**

     * 生成指定字符串的圖像數據

     * @param verifyCode 即將被打印的隨機字符串

     * @return 生成的圖像數據

     * */

    private BufferedImage getImage(String verifyCode){

        BufferedImage image = new BufferedImage(WIDTH * CODE_LENGTH, HEIGHT, BufferedImage.TYPE_INT_RGB);

        //獲取圖形上下文

        Graphics graphics = image.getGraphics();

        //設置背景色

        graphics.setColor(getRandColor(1,50));

        //填充背景色

        graphics.fillRect(0, 0, WIDTH * 4, HEIGHT);

        //設置邊框顏色

        graphics.setColor(new Color(0,255,0));

        //畫邊框

    /*    for (int i=0; i<2; i++)

            graphics.drawRect(i, i, WIDTH * CODE_LENGTH - i * 2 - 1, HEIGHT - i * 2 - 1); */

        //設置隨機干擾線條顏色

        graphics.setColor(getRandColor(50,100));

        //產生50條干擾線條

        for (int i=0; i<50; i++){

            int x1 = random.nextInt(WIDTH * CODE_LENGTH - 4) + 2;

            int y1 = random.nextInt(HEIGHT - 4) + 2;

            int x2 = random.nextInt(WIDTH * CODE_LENGTH - 2 - x1) + x1;

            int y2 = y1;

            graphics.drawLine(x1, y1, x2, y2);

        }

        //設置字體

        graphics.setFont(new Font("Times New Roman", Font.PLAIN, 18));

        //畫字符串

        for (int i=0; i<this.CODE_LENGTH; i++){

            String temp = verifyCode.substring(i, i+1);

            graphics.setColor(getRandColor(100,255));

            graphics.drawString(temp, 13 * i + 6, 16);

        }

        //圖像生效

        graphics.dispose();

        return image;

    }

    /**

     * 將驗證碼的圖像輸出

     * @param request 用戶的請求對象

     * @param response 用戶的響應對象

     * */

    public void printImage(HttpServletRequest request,

            HttpServletResponse response){

        //將ContentType設為"image/jpeg"，讓瀏覽器識別圖像格式。

        response.setContentType("image/jpeg");

        //設置頁面不緩存

        response.setHeader("Pragma", "No-cache");

        response.setHeader("Cache-Control", "no-cache");

        response.setDateHeader("Expires", 2000);

        //獲得隨機驗證碼

        String verifyCode = this.getRandString();

        String str = "ssss";

        for(int i=0; i<10; i++)

            str = str + str;

        //獲得驗證碼的圖像數據

        BufferedImage bi = this.getImage(verifyCode);

        //把驗證碼存入session

        request.getSession().setAttribute(ATTRIBUTE_NAME, verifyCode);

        try{

            //獲得Servlet輸出流

            ServletOutputStream outStream = response.getOutputStream();

            //創建可用來將圖像數據編碼為JPEG數據流的編碼器

            JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(outStream);

            //將圖像數據進行編碼

            encoder.encode(bi);

            //強行將緩沖區的內容輸入到頁面

            outStream.flush();

            //關閉輸出流

            outStream.close();

        }catch(IOException ex){

            ex.printStackTrace();

        }

    }

    /**

     * 檢查輸入的驗證碼是否正確，若用戶輸入的驗證碼與生成的驗證碼相符則返回true，否則返回false。

     * @param request 用戶的請求對象

     * @return 驗證結果

     * */

    public boolean check(HttpServletRequest request){

        if (((String)request.getParameter(ATTRIBUTE_NAME))

                .equalsIgnoreCase((String)request.getSession().getAttribute(ATTRIBUTE_NAME))){

            request.getSession().removeAttribute(ATTRIBUTE_NAME);

            return true;

        }

        return false;

    }

}

2.        編寫servlet顯示圖片信息

package com.xia;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.io.IOException;

public class CreateCode extends HttpServlet {

    public void service(HttpServletRequest request, HttpServletResponse response)

       throws ServletException, IOException

       {

          VerifyCodeGenerator ver=new VerifyCodeGenerator();

          ver.printImage(request, response);

       }

}

3.        編寫HTML頁面：

<%@ page language="java" pageEncoding="utf-8"%>

<%String path = request.getContextPath();

  String basePath = request.getScheme() + "://"

         + request.getServerName() + ":" + request.getServerPort()

         + path + "/";

%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

  <head>

     <base href="<%=basePath%>">

     <title>My JSP 'index.jsp' starting page</title>

     <meta http-equiv="pragma" content="no-cache">

     <meta http-equiv="cache-control" content="no-cache">

     <meta http-equiv="expires" content="0">

     <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">

     <meta http-equiv="description" content="This is my page">

     <!--

  <link rel="stylesheet" type="text/css" href="styles.css">

  -->

  </head>

  <script type="text/javascript">

  function show()

  {

  var o=document.getElementById("random");

  var timenow = new Date().getTime();

  o.src="/ValidateCodeDemo/CreateCode";

  }

  </script>

  <body>

     This is my JSP page.

     <input type="text"/>

     <br>

     <input type="image" src="/ValidateCodeDemo/CreateCode" name="random" width="80px" height="30px"/>

<!--   刷新驗證碼  -->

     <a href="javaScript:show()">看不清楚，換一張</a>

  </body>

</html>