jsp页面验证码完整实例

package com.servlet;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class IdentityServlet extends HttpServlet {

  public static final char[] chars={'2','3','4','5','6','7','8','9','A'};//自定义验证码池
  public static Random random=new Random();　　//随机数
  
  public static String getRandomString(){　　//获取6位随机数，放在图片里
    StringBuffer buffer=new StringBuffer();
    for(int i=0;i
   */
  public void destroy() {
    super.destroy(); // Just puts "destroy" string in log
    // Put your code here
  }

  /**
   * The doGet method of the servlet. 

   *
   * 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");　　//设置输出类型
    
    String randomString = getRandomString();　　//随机字符串
    request.getSession(true).setAttribute("randomString", randomString);//放到session里
    
    int width=100;　　//图片宽度
    int height=30;　　//图片高度
    
    Color color=getRandomColor();　　//随机颜色，用于背景色
    Color reverse=getReverseColor(color);//反色，用于前景色
    //创建一个彩色图片
    BufferedImage bi=new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
    Graphics2D g=bi.createGraphics();　　//绘图对象
    g.setFont(new Font(Font.SANS_SERIF,Font.BOLD,16));//设置字体
    g.setColor(color);//设置颜色
    g.fillRect(0, 0, width, height);//绘制背景
    g.setColor(reverse);
    g.drawString(randomString, 18, 20);//绘制随机字符
    for(int i=0,n=random.nextInt(100);i
   *
   * 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. 

   *
   * @throws ServletException if an error occurs
   */
  public void init() throws ServletException {
    // Put your code here
  }

}

IdentityServletcom.servlet.IdentityServletIdentityServlet/servlet/IdentityServletindex.jsp