checkcodeservlet.java

java的一个验证码登陆系统 随机生成验证码图片 0-9 a-z 可以作为登陆参考

package org.yzm.utils;

import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.awt.Color;
import java.awt.Font;
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;

public class CheckCodeServlet extends HttpServlet {
	private static int WIDTH=60;
    private static int HEIGHT=20;

	public CheckCodeServlet() {
		super();
	}

	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 {
		HttpSession session = request.getSession();    
        response.setContentType("image/jpeg");
        ServletOutputStream sos = response.getOutputStream();
        
        response.setHeader("Pragma", "No-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
        
        BufferedImage image = new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB);
        Graphics g=image.getGraphics();
        
        char[] rands = generateCheckCode();
        drawBackground(g);
        drawRands(g,rands);
        g.dispose();
        
        ByteArrayOutputStream bos= new ByteArrayOutputStream();
        ImageIO.write(image,"JPEG",bos);
        byte[] buf = bos.toByteArray();
        response.setContentLength(buf.length);
        sos.write(buf);
        bos.close();
        sos.close();
        session.setAttribute("check_code", new String(rands));


	}
	
	   private void drawBackground(Graphics g){
	        g.setColor(new Color(0xDCDCDC));
	        g.fillRect(0, 0, WIDTH, HEIGHT);
	        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);
	        }
	    }

	    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);
	    }

	    private char[] generateCheckCode(){
	        String chars = "0123456789abcdefghijklmnopqrstuvwxyz";
	        char[] rands = new char[4];
	        for(int i=0;i<4;i++){
	            int rand = (int)(Math.random()*36);
	            rands[i]=chars.charAt(rand);
	        }
	        return rands;
	    }


	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		 this.doGet(request, response);

	}

	public void init() throws ServletException {

	}

}