SafeCode.java
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package com.bjivt.web.servlet;
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.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
@SuppressWarnings("serial")
public class SafeCode extends HttpServlet {
private static final long serialVersionUID = -8584041841501416165L;
static{
System.setProperty("java.awt.headless", "true");
}
private static int WIDTH = 60;
private static int HEIGHT = 20;
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
HttpSession session = request.getSession();
// 设置浏览器不要缓存此图片
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
response.setContentType("image/jpeg");
// 创建内存图象并获得其图形上下文
BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
// 产生随机的认证码并画图
char[] rands = this.generateCheckCode();
this.drawBackground(g);
this.drawRands(g, rands);
// 结束图像的绘制过程，完成图像
g.dispose();
// 将当前验证码存入到Session中
session.setAttribute("rand", new String(rands));
// 将图像输出到客户端
// JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(response.getOutputStream());
// encoder.encode(image);
ServletOutputStream out = null;
out = response.getOutputStream();
ImageIO.write(image, "JPEG", response.getOutputStream());
out.flush();
//ServletActionContext.getPageContext().pushBody();
out.close();
}
/**
* 产生随机数。
* @return
*/
private char[] generateCheckCode()
{
// 定义验证码的字符表
String chars = "0123456789";
char[] rands = new char[4];
for (int i = 0; i < 4; i++)
{
int rand = (int) (Math.random() * 10);
rands[i] = chars.charAt(rand);
}
return rands;
}
/**
* 画随机数。
* @param g
* @param rands
*/
private void drawRands(Graphics g, char[] rands)
{
g.setColor(Color.BLACK);
g.setFont(new Font(null, Font.PLAIN | Font.BOLD |Font.ITALIC|Font.TRUETYPE_FONT, 18));
// 在不同的高度上输出验证码的每个字符
g.drawString("" + rands[0], 1, 17);
g.drawString("" + rands[1], 16, 15);
g.drawString("" + rands[2], 31, 18);
g.drawString("" + rands[3], 46, 16);
}
/**
* 画图片背景。
* @param g
*/
private void drawBackground(Graphics g)
{
g.setColor(new Color(0xDCDCDC));
g.fillRect(0, 0, WIDTH, HEIGHT);
// 随机产生120个干扰点
for (int i = 0; i < 120; i++)
{
int x = (int) (Math.random() * WIDTH);
int y = (int) (Math.random() * HEIGHT);
int red = (int) (Math.random() * 255);
int green = (int) (Math.random() * 255);
int blue = (int) (Math.random() * 255);
g.setColor(new Color(red, green, blue));
g.drawOval(x, y, 1, 0);
}
}
}