Servlet代码生成验证码

package com.test;

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

public class TestIMGEServlet extends HttpServlet {

  private static final long serialVersionUID = 1L; public static final String VALIDATE_CODE_SESSION_KEY="VALIDATE_CODE_SESSION_KEY"; public void doGet(HttpServletRequest request, HttpServletResponse response)   throws ServletException, IOException {  doPost(request, response); } public void doPost(HttpServletRequest request, HttpServletResponse response)   throws ServletException, IOException {  response.setContentType("image/png");  String code =  createValidateCode();  request.getSession().setAttribute(VALIDATE_CODE_SESSION_KEY, code);  Color []c = new Color[]{Color.RED,Color.BLUE,Color.green,Color.BLACK};  //生成这么大小的图片  BufferedImage image = new BufferedImage(120, 40, BufferedImage.TYPE_INT_RGB);  //生成画笔  Graphics g = image.getGraphics();  //把生成的图片的背景色设置一下  淡灰色的  g.setColor(Color.GRAY.brighter());  g.fillRect(0, 0, image.getWidth(), image.getHeight());  Random r = new Random();  for (int i = 0; i < 20; i++) {   g.setColor(new Color(r.nextInt(256), r.nextInt(256), r.nextInt(256)));   g.drawOval(r.nextInt(image.getWidth())/2, r.nextInt(image.getHeight())/2, r.nextInt(image.getWidth()), r.nextInt(image.getHeight()));     }  Font f = new Font("IMPACT", Font.BOLD, 30);  g.setFont(f);  for (int i = 0; i < code.length(); i++) {   int y = r.nextInt(20)+20;   //g.setColor(Color.black);   //g.drawString(""+code.charAt(i), image.getWidth()/code.length()*i, 20);   g.setColor(c[i]);   g.drawString(""+code.charAt(i), image.getWidth()/code.length()*i, y);  }  System.out.println(request.getSession().getAttribute(VALIDATE_CODE_SESSION_KEY));  ImageIO.write(image, "png", response.getOutputStream());     } public String createValidateCode(){  String charNumber = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";  Random r = new Random();  return ""+charNumber.charAt(r.nextInt(charNumber.length()))+charNumber.charAt(r.nextInt(charNumber.length()))+charNumber.charAt(r.nextInt(charNumber.length()))+charNumber.charAt(r.nextInt(charNumber.length())); }

}