java生成验证图片，很好用的

来源：互联网发布：python apply async 编辑：程序博客网时间：2024/05/22 16:07

========================jsp==============================
function changeImg(){
var a=document.getElementById("mySpan");

//最好在"/ImageServlet?now='+new Date()+'"/>否则有些浏览器支持的不够好
a.innerHTML='<img align="middle" src="ImageServlet"/> <a href="#" onclick="changeImg();">看不清，换一张！</a>'; //会复盖“mySpan”位置
}

=====================web.xml=================
<servlet>
    <servlet-name>ImageServlet</servlet-name>
    <servlet-class>com.e8online2.comm.util.IdentifyingServlet</servlet-class>
</servlet>
   <servlet-mapping>
    <servlet-name>ImageServlet</servlet-name>
    <url-pattern>/ImageServlet</url-pattern>
</servlet-mapping>

/=======================最后从session中获取原来的验证码与jsp中上传的验证码比较就可以了=================

package com.e8online2.comm.util;

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 IdentifyingServlet extends HttpServlet {

/**
*
*/
private static final long serialVersionUID = 1L;

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

response.setContentType("image/jpeg");

  // 给定范围获得随机颜色
  // 设置页面不缓存
  response.setHeader("Pragma", "No-cache");
  response.setHeader("Cache-Control", "no-cache");
  response.setDateHeader("Expires", 0);

  // 在内存中创建图象
  int width = 60, height = 17;
  BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

// 获取图形上下文
Graphics g = image.getGraphics();

// 生成随机类
Random random = new Random();

  // 设定背景色
  g.setColor(getRandom(254, 255));
  g.fillRect(0, 0, width, height);

// 设定字体
g.setFont(new Font("Cooper Black", Font.PLAIN, 18));

  // 画边框
  // g.setColor(new Color());
  // g.drawRect(0,0,width-1,height-1);

  // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
  g.setColor(getRandom(230, 240));
  for (int i = 0; i < 155; i++) {
   int x = random.nextInt(width);
   int y = random.nextInt(height);
   int xl = random.nextInt(12);
   int yl = random.nextInt(12);
   g.drawLine(x, y, x + xl, y + yl);
  }

  // 取随机产生的认证码(4位数字)
  String sRand = "";
  for (int i = 0; i < 4; i++) {
   String rand = String.valueOf(random.nextInt(10));
   sRand += rand;
   // 将认证码显示到图象中
   g.setColor(new Color(100 + random.nextInt(130), 100 + random.nextInt(130), 100 + random.nextInt(130)));// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
   g.drawString(rand, 13 * i + 6, 14);
  }

// 将认证码存入SESSION
request.getSession().setAttribute("IdentifyingCode", sRand);

// 图象生效
g.dispose();

// 输出图象到页面
ImageIO.write(image, "JPEG", response.getOutputStream());
}

private Color getRandom(int mixValue, int maxValue) {
  Random random = new Random();
  if (mixValue > 255)
   mixValue = 255;
  if (maxValue > 255)
   maxValue = 255;
  // int r=fc+random.nextInt(bc-fc);
  // int g=fc+random.nextInt(bc-fc);
  // int b=fc+random.nextInt(bc-fc);
  // return new Color(r,g,b);
  int rgb = mixValue + random.nextInt(maxValue - mixValue);
  return new Color(rgb, rgb, rgb);
}

}