验证码

package 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.ServletRequest;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class yanzhengma extends HttpServlet {

	/**
		 * Constructor of the object.
		 */
	public yanzhengma() {
		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 {
         response.setContentType("image/jpeg");
         HttpSession session=request.getSession();
         int width =60;
         int height=20;
         response.setHeader("Paragma", "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="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
         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();
         HttpSession  session1 = request.getSession();
		session1.setAttribute("checkCode",new String(rands));
   }
	/**
		 * The doPost method of the servlet. <br>
		 *
		 * This method is called when a form has its tag value method equals to post.
		 * 
		 * @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 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
	}

}

　　以上便是验证码的生成servlet