java 验证码

 

package com.lk.test;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
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 RequestServlet extends HttpServlet{

 /**
  * 定义序列版本号
  */
 private static final long serialVersionUID = 1L;
 
 public static final char[]chars = {'2','3','4','5','6','7','8','9','A','B',
  'C','D','E','F','G','H','J','K','L','M','N','P','Q','R','S','T','U','V','W',
  'X','Y','Z'};
 
 public static Random random = new Random();
 
 //获取六位随机数
 public static String getRandomString(){
  StringBuffer stringBuffer = new StringBuffer();
  for (int i = 0; i < 6; i++) {
   stringBuffer.append(chars[random.nextInt(chars.length)]);
  }
  return stringBuffer.toString();
 }
 
 //获取随机颜色
 public static Color getRandomColor(){
  return new Color(random.nextInt(255),random.nextInt(255),random.nextInt(255));
 }
 
 //获取莫颜色的反色
 public static Color getReverseColor(Color c){
  return new Color(random.nextInt(255-c.getRed()),random.nextInt(255-c.getGreen()),random.nextInt(255-c.getBlue()));
 }
 
 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp)
   throws ServletException, IOException {
  
  //设置输出类型
  resp.setContentType("image/jpeg");
  //获取随机字符串
  String randomString = getRandomString();
  //随机字符串放入session中
  req.getSession(true).setAttribute("randomString", randomString);
  //图片宽度
  int width=100;
  //图片高度
  int height=30;
  //随机颜色用于字体颜色
  Color color = getRandomColor();
  //反色用于背景颜色
  Color reverseColor = getReverseColor(color);
  
  //创建一个彩色图片
  BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_BGR);
  
  //获取绘图对象
  Graphics2D g = bi.createGraphics();
  //设置字体
  g.setFont(new Font(Font.SANS_SERIF,Font.BOLD,16));
  
  //设置字体颜色
  g.setColor(color);
  //绘制背景
  g.fillRect(0, 0, width, height);
  //设置背景色
  g.setColor(reverseColor);
  //绘制随机字符
  g.drawString(randomString, 18, 20);
  
  //画最多100个噪音点
  for (int i = 0; i < random.nextInt(100); i++) {
    //随机噪音点
    g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1);
  }
  //输出流
  ServletOutputStream out = resp.getOutputStream();
  //编码器对象 把流转化成JPEG格式
  JPEGImageEncoder encode = JPEGCodec.createJPEGEncoder(out);
  
  //对图片进行编码
  encode.encode(bi);
  out.flush();
  out.close();
  
 }
 
}

 

 

前台代码：

<script type="text/javascript">
 function reloadImage(){
  document.getElementById("btn").disabled=true;
  document.getElementById("identity").src="RequestServlet?ts="+new Date().getTime();
 }
 </script>

<img  src="RequestServlet" id="identity" onload="btn.disabled=false;">  
    <input type="button" value="换个图片" id="btn" onclick="reloadImage()"/>

"RequestServlet“为映射路径