checkcode.java

一个学生选课系统

package com.student.action;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
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;
import javax.servlet.http.HttpSession;

public class CheckCode extends HttpServlet {

	/**
	 * Constructor of the object.
	 */
	public CheckCode() {
		super();
	}

	/**
	 * Destruction of the servlet. <br>
	 */
	public void destroy() {
		super.destroy(); // Just puts "destroy" string in log
		// Put your code here
	}

	
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		// 产生一副图像
		// //设置页面不缓存
		response.setHeader("Pragma", "No-cache");
		response.setHeader("Cache-Control", "no-cache");
		response.setDateHeader("Expires", 0);

		// 生成随机类
		Random random = new Random();
		System.out.println("heiheiheihei");
		// 设置验证码的位数
		int length = 5;
		// 产生验证码
		String checkcode = "";
		char code;
		int number;
		/*String chinese = "网站的内容需要授权才能访问";

		for (int i = 0; i < length; i++) {

			number = random.nextInt(chinese.length());

			code = chinese.charAt(number);

			checkcode += code;

		}
		System.out.println(checkcode);*/

		for(int i=0; i<length; i++)
		 {
		 number = random.nextInt(26);
		 
			        
		 if(number % 2 == 0) //0-9数字
		 code = (char)('0' + (char)(number % 10));
		 else // A-Z
		 code = (char)('A' + (char)(number % 26));
		
		 checkcode += code+"";
		}

		// 在内存中创建图象
		int width = (int) Math.ceil(length * 16), height = 22;
		BufferedImage image = new BufferedImage(width, height,
				BufferedImage.TYPE_INT_RGB);

		// 获取图形上下文
		Graphics g = image.getGraphics();

		// 设定背景色
		g.setColor(Color.WHITE);
		g.fillRect(0, 0, width, height);

		// 画边框
		g.setColor(Color.GRAY);
		g.drawRect(0, 0, width - 1, height - 1);

		// 随机产生25条干扰线，使图象中的认证码不易被其它程序探测到

		for (int i = 0; i < 25; i++) {
			int x1 = random.nextInt(width);
			int y1 = random.nextInt(height);
			int x2 = random.nextInt(width);
			int y2 = random.nextInt(height);
			g.setColor(Color.GRAY);
			g.drawLine(x1, y1, x2, y2);
		}

		// 设定字体,画验证码
		g.setColor(Color.BLUE);
		g.setFont(new Font("Arial", Font.BOLD | Font.ITALIC,18));
		g.drawString(checkcode, 5, 18);

		// 将认证码存入SESSION
		// session
		HttpSession session = request.getSession();
		request.setAttribute("rando",checkcode);
		session.setAttribute("rando", checkcode);
		System.out.println(checkcode);

		// 图象生效
		g.dispose();

		// 输出图象到页面,
		// response.getOutputStream() 响应所对应的输出流
		// 图像显示在页面上
		ImageIO.write(image, "JPEG", response.getOutputStream());

		// 把图像显示在页面上
	}

	
	
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		doGet(request, response);
	}

	/**
	 * Initialization of the servlet. <br>
	 *
	 * @throws ServletException if an error occurs
	 */
	public void init() throws ServletException {
		// Put your code here
	}

}