import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class CheckcodeServlet extends HttpServlet {
private int width = 80;
private int height = 30;
public void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//阶段一：绘图。
// 创建一个内存映像对象 (画布)
BufferedImage image =
new BufferedImage(width,height,
BufferedImage.TYPE_INT_RGB);
// 获得画笔
Graphics g = image.getGraphics();
// 给画笔设置颜色
Random r = new Random();
g.setColor(new Color(r.nextInt(255),
r.nextInt(255),r.nextInt(255)));
// 给画布设置背景颜色
g.fillRect(0, 0, width, height);
// 将一个随机数画在画布上
String number = getNumber(5);
//将随机数绑订到session对象上
HttpSession session = request.getSession();
session.setAttribute("number", number);
g.setColor(new Color(0,0,0));
//设置字体
g.setFont(new Font(null,
Font.ITALIC|Font.BOLD,20));
g.drawString(number, 5, 22);
//加一些干扰线
for(int i=0;i<8;i++){
g.setColor(new Color(r.nextInt(255),
r.nextInt(255),r.nextInt(255)));
g.drawLine(r.nextInt(width),
r.nextInt(height),
r.nextInt(width),
r.nextInt(height));
}
//阶段二: 将图片压缩，输出到浏览器。
response.setContentType("image/jpeg");
OutputStream ops =
response.getOutputStream();
//write方法将原始图片压缩，然后发送给
//response对象。
javax.imageio.ImageIO
.write(image, "jpeg", ops);
}
private String getNumber(int size) {
String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" +
"0123456789";
Random r = new Random();
String number = "";
for(int i=0;i<size;i++){
number += str.charAt(
r.nextInt(str.length()));
}
return number;
}
}
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