JavaWeb_Servlet_应用_验证码

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http://blog.csdn.net/zimo2013/article/details/9082771

/*
 * 验证码
 * http://blog.csdn.net/strawberry2013
 * 2013-6-5
 */
package cn.baidu;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ServletImage extends HttpServlet {
	
	private static final int WIDTH = 150;
	private static final int HEIGHT = 35;
	
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
	
		//告诉浏览器不要缓存
		response.setDateHeader("expries", -1);
		response.setHeader("Cache-Control", "no-cache");
		response.setHeader("Pragma", "no-cache");
		
		//设置类型
		response.setContentType("image/jpeg");
		
		//新建BufferedImage，通过getGraphics方法得到画板
		BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
		Graphics g = image.getGraphics();
		
		//将画板的填充为白色
		g.setColor(Color.WHITE);
		g.fillRect(0, 0, WIDTH, HEIGHT);
		
		//将画板的边框画上
		g.setColor(Color.BLUE);
		g.drawRect(1, 1, WIDTH-2, HEIGHT-2);
		
		//产生随机的线条
		g.setColor(Color.GREEN);
		for(int i=0; i<5; i++){
			int x1 = new Random().nextInt(WIDTH);
			int y1 = new Random().nextInt(HEIGHT);
			int x2 = new Random().nextInt(WIDTH);
			int y2 = new Random().nextInt(HEIGHT);
			g.drawLine(x1, y1, x2, y2);
		}
		
		//写上字并旋转
		g.setColor(Color.RED);
		g.setFont(new Font("宋体", Font.BOLD, 30));
		String str = "请按照网上邪恶的插入法提供必要花奴家米科利";
		int x = 5;
		Graphics2D gg = (Graphics2D) g;
		for(int i=0; i<4; i++){
			int angle = new Random().nextInt(40) -20;	//产生随机的角度
			gg.rotate(angle*Math.PI/180, x, 30);		//旋转画板
			int start = new Random().nextInt(str.length());
			g.drawString(str.substring(start, start+1), x, 25);	//写上字
			gg.rotate(-angle*Math.PI/180, x, 30);		//将画板重新还原
			x += 35;
		}
		
		//将image 写入到流中
		ImageIO.write(image, "jpg", response.getOutputStream());
	}
}