codemakerservlet.java

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// Fig. 5.6_01:  CodeMakerServlet.java
// 生成验证码的Servlet

package com.fatcat.webchart;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.awt.image.*;
import java.awt.*;
import javax.imageio.*;

public class CodeMakerServlet extends HttpServlet
{
    private Font[] codeFont =
    {
        new Font("Algerian", Font.BOLD, 65), 
		new Font("Vivaldi", Font.BOLD, 85),
        new Font("Broadway", Font.BOLD, 60),
		new Font("Forte", Font.BOLD, 75)
    };

    private Color[] color =
    {
       Color.BLACK, Color.RED, Color.DARK_GRAY, Color.BLUE
    };

    String codeNumbers = "";

    int width = 250, height = 70;

    // 处理 HTTP get 请求
    public void doGet(HttpServletRequest request, HttpServletResponse response)
                      throws ServletException, IOException
    {
        // 清空缓冲区
        response.reset();

        // 注意这里的MIME类型
        response.setContentType("image/png");

        // 设置页面不缓存
        response.setHeader("Pragma", "No-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);

        // 创建一个 250X70 的图像
        BufferedImage image = new BufferedImage(width, height,
                                                BufferedImage.TYPE_INT_RGB);

        // 得到图形环境对象 g
        Graphics g = image.getGraphics();

        // 填充背景
        g.setColor(Color.YELLOW);
        g.fillRect(0, 0, width, height);

        for (int i = 0; i < 4; i++)
        {
            drawCode(g, i);
        }

        drawNoise(g, 30);

        // 绘制边框
        g.setColor(Color.black);
        g.drawRect(0, 0, width - 1, height - 1);

        // 将验证码内容保存进session中
        HttpSession session = request.getSession(true);
        session.setAttribute("codeNumbers", codeNumbers);
        
		// 重设字符串
        codeNumbers = "";

        // 利用ImageIO类的write方法对图像进行编码
        ServletOutputStream sos = response.getOutputStream();
        ImageIO.write(image, "PNG", sos);
        sos.close();
    }

    // 绘制验证码
    public void drawCode(Graphics graphics, int i)
    {
        int number = (int)(Math.random() * 10);
        graphics.setFont(codeFont[i]);
        graphics.setColor(color[i]);
        graphics.drawString("" + number, 10 + i * 60, 60);

        codeNumbers += number;
    }

    // 绘制干扰线
    public void drawNoise(Graphics graphics, int lineNumber)
    {
        graphics.setColor(Color.YELLOW);
        for (int i = 0; i < lineNumber; i++)
        {
            int pointX1 = 1 + (int)(Math.random() * width);
            int pointY1 = 1 + (int)(Math.random() * height);
            int pointX2 = 1 + (int)(Math.random() * width);
            int pointY2 = 1 + (int)(Math.random() * height);
            graphics.drawLine(pointX1, pointY1, pointX2, pointY2);
        }
    }
    // 处理 HTTP post 请求, 和doGet一样
    public void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException
    {
        doGet(request, response);
    }
}


/**************************************************************************
 * (C) Copyright 2004-2005 by Jingkui Zhong(钟京馗) and Huan Tang(唐桓).  *
 * All Rights Reserved.                                                   *
 *                                                                        *
 * DISCLAIMER: The authors of this code have used their                   *
 * best efforts in preparing the code. These efforts include the          *
 * development, research, and testing of the theories and programs        *
 * to determine their effectiveness. The authors and publisher make       *
 * no warranty of any kind, expressed or implied, with regard to these    *
 * programs or to the documentation contained in these codes. The authors *
 * shall not be liable in any event for incidental or consequential       *
 * damages in connection with, or arising out of, the furnishing,         *
 * performance, or use of these programs.                                 *
  **************************************************************************/