checkcodeservlet.java

一个较简单的论坛——中国精英论坛,是我的一个练习

package com.servlet;

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.awt.*;
import java.awt.image.*;
import javax.imageio.ImageIO;

public class CheckCodeServlet extends HttpServlet {

	private static int 	WIDTH=60;
	private static int HIGHT=20;
	
	/**
	 * Constructor of the object.
	 */
	public CheckCodeServlet() {
		super();
	}

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

	/**
	 * The doGet method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to get.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		HttpSession session=request.getSession();
		response.setContentType("image/jpeg");
		ServletOutputStream sos=response.getOutputStream();
		
		//设置浏览器不要缓存图片
		//response.setHeader("Pragma", "No-cache");
		//response.setHeader("Cache-control","no-cache");
		//response.setDateHeader("Expires",0);
		
		//创建内存图像并获得图形上下文
		
		BufferedImage image=
			new BufferedImage(WIDTH,HIGHT,BufferedImage.TYPE_INT_RGB);
		Graphics g=image.getGraphics();
		
		//产生随机的验证码
		char [] rands=generateCheckCode();
		
		//产生图像
		drawBackground(g);
		drawRands(g,rands);
		
		//结束图像制作，完成图像
		g.dispose();
		
		//将图像绘制到客户端
		ByteArrayOutputStream bos=new ByteArrayOutputStream();
		ImageIO.write(image, "JPEG", bos);
		byte [] buf=bos.toByteArray();
		response.setContentLength(buf.length);
		sos.write(buf);
		bos.close();
		sos.close();
		
		//将当前的验证码输出到session
		session.setAttribute("check_code", new String(rands));
		System.out.println(new String(rands));
	}
	
	//获得随机字符
	private char [] generateCheckCode()
	{
		String chars="0123456789abcdefghigklmnopqrstuvwxyzABCDEFGHIGKLMNOPQRSTUVWXYZ";
		char [] rands=new char[4];
		for(int i=0;i<4;i++)
		{
			int rand=(int)(Math.random()*62);
			rands[i]=chars.charAt(rand);
		}
		return rands;
	}
	
	
	//画字符串
	private void drawRands(Graphics g,char [] rands)
	{
		g.setColor(Color.BLACK);
		g.setFont(new Font(null,Font.ITALIC|Font.BOLD,18));
		g.drawString(""+rands[0],1,17);
		g.drawString(""+rands[1],16,15);
		g.drawString(""+rands[2],31,18);
		g.drawString(""+rands[3],46,16);
		System.out.println(rands);
	}
	
	
	//画背景
	private void drawBackground(Graphics g)
	{
		g.setColor(new Color(0xDCDCDC));
		g.fillRect(0, 0, WIDTH, HIGHT);
		for(int i=0;i<120;i++)
		{
			int x=(int)(Math.random()*WIDTH);
			int y=(int)(Math.random()*HIGHT);	
			int red=(int)(Math.random()*255);
			int blue=(int)(Math.random()*255);
			int green=(int)(Math.random()*255);
			g.setColor(new Color(red,green,blue));
			g.drawOval(x, y,1,0);
		}	
	}

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

		//doGet(request,response);
	}

	public void init() throws ServletException {
		// Put your code here
	}

}