imageservlet.java

JBuilder 2006 +SQL Server2000 +JavaBean+JSP开发的宠物医院管理系统

package com.pet.util;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.awt.Color;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.awt.Graphics;
import java.awt.Font;

public class ImageServlet extends HttpServlet {
    private static final String CONTENT_TYPE = "text/html; charset=GBK";
    private static final long serialVersionUID = 8109503217290526554L;
    private static final Font FONT = new Font("Times New Roman", Font.ITALIC,
                                              18);
    //new Font("Times New Roman",Font.ITALIC,18)
    private int defaultWidth; // 图片宽度
    private int defaultHeight; // 图片高度
    private int defaultLength; // 生成随机字母长度
    private String defaultKey = "checkRand"; // 保存在会话中的key值

    public void init() throws ServletException {
        super.init();
        String key = this.getInitParameter("key");
        if (key != null && key.equals("")) {
            defaultKey = key;
        }

        String width = this.getInitParameter("width");
        try {
            defaultWidth = Integer.parseInt(width);
        } catch (NumberFormatException e) {
            defaultWidth = 60;
        }

        String height = this.getInitParameter("height");
        try {
            defaultHeight = Integer.parseInt(height);
        } catch (NumberFormatException e) {
            defaultHeight = 18;
        }

        String length = this.getInitParameter("length");
        try {
            defaultLength = Integer.parseInt(length);
        } catch (NumberFormatException e) {
            defaultLength = 4;
        }
    }

    private int getImageWidth(String widtha) {
        int width = 0;
        try {
            width = Integer.parseInt(widtha);
        } catch (NumberFormatException e) {
            width = defaultWidth;
        }
        return width;
    }

    private int getImageHeight(String heighta) {
        int height = 0;
        try {
            height = Integer.parseInt(heighta);
        } catch (NumberFormatException e) {
            height = defaultHeight;
        }
        return height;
    }

    private int getLength(String lengtha) {
        int length = 0;
        try {
            length = Integer.parseInt(lengtha);
        } catch (NumberFormatException e) {
            length = defaultLength;
        }
        return length;
    }

    private 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);
    }

    //Process the HTTP Get request
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws
            ServletException, IOException {
         response.setHeader("Pragma", "No-cache"); // 设置响应的文件头
         response.setHeader("Cache-Control", "no-cache");
         response.setDateHeader("Expires", 0);
         response.setContentType("image/jpeg"); // 表明生成的响应是图片，而非JSP页面


         String key = request.getParameter("key");
         if (key == null || key.equals("")) {
             key = defaultKey;
         }
         int width = getImageWidth(request.getParameter("width"));
         int height = getImageHeight(request.getParameter("height"));
         int length = getLength(request.getParameter("length"));

         // 在内存中生成图片
         BufferedImage image = new BufferedImage(width, height,
                                                 BufferedImage.TYPE_INT_RGB);

         // 开始制作图像
         Graphics graphics = image.getGraphics();
         Random random = new Random();
         graphics.setColor(getRandColor(200, 250));
         graphics.fillRect(1, 1, width - 1, height - 1);
         graphics.setColor(new Color(102, 102, 102));
         graphics.drawRect(0, 0, width - 1, height - 1);
         graphics.setFont(FONT);
         graphics.setColor(getRandColor(160, 200));

         // 画随机线条
         for (int i = 0; i < 155; i++) {
             int x = random.nextInt(width - 1);
             int y = random.nextInt(height - 1);
             int x1 = random.nextInt(6) + 1;
             int y1 = random.nextInt(12) + 1;
             graphics.drawLine(x, y, x + x1, y + y1);
         }

         // 从另一个方向画随机线条
         for (int i = 0; i < 70; i++) {
             int x = random.nextInt(width - 1);
             int y = random.nextInt(height - 1);
             int x1 = random.nextInt(12) + 1;
             int y1 = random.nextInt(6) + 1;
             graphics.drawLine(x, y, x - x1, y - y1);
         }

         // 生成随机数，并将随机数转换成字母
         String sRand = "";
         for (int i = 0; i < length; i++) {
             int itmp = random.nextInt(26) + 65;
             char ctmp = (char) itmp;
             sRand += String.valueOf(ctmp);
             graphics.setColor(new Color(20 + random.nextInt(110), 20 + random
                                         .nextInt(110), 20 + random.nextInt(110)));
             graphics.drawString(String.valueOf(ctmp), 12 * i + 3, 16);
         }

         //如果布尔值为true且当前没有与请求关联的会话，则使用getSession(boolean value)会创建一个新会话
         HttpSession session = request.getSession(true);
         session.setAttribute("key", sRand); //将验证码放入会话当中
         graphics.dispose();

         ImageIO.write(image, "JPEG", response.getOutputStream()); // 输出图片到Servlet响应
     }

    }