图形验证码生成servlet

图形验证码生成servlet

import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.PrintWriter;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 checkcode extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setContentType("image/jpeg");HttpSession session=request.getSession();int width=60;int height=20;response.setHeader("Pargma","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();String chars="0123456789ABCDEFGHIJKLMNOBQRSTUVWXYZ";char[] rands=new char[4];for(int i=0;i<4;i++){int rand=(int)(Math.random()*36);rands[i]=chars.charAt(rand);}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);}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);g.dispose();ServletOutputStream sos=response.getOutputStream();ByteArrayOutputStream baos=new ByteArrayOutputStream();ImageIO.write(image,"JPEG", baos);byte[] buffer=baos.toByteArray();response.setContentLength(buffer.length);sos.write(buffer);baos.close();sos.close();session.setAttribute("checkCode", new String(rands));}}