图片验证码

假设有两个jsp和一个java文件。

userLogin.jsp

<tr>
    <td class="STYLE1">
        <span id="check_code">验 证 码：&nbsp;&nbsp;</span>
		<span>
            <img id="imgCheckCode" src="inc/img.jsp" alt="点击刷新验证码" style="cursor:pointer;border:0;height:20px;margin-left:-2px;" onclick="this.src='inc/img.jsp?t='+Math.random()">
        </span>
	</td>
</tr>

img.jsp

<%@page import="com.ufgov.portal.web.util.CheckCode"%>
<%@ page contentType="image/jpeg; charset=UTF-8"
	import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*,java.io.*"%>
<%
	response.setHeader("Pragma", "No-cache");
	response.setHeader("Cache-Control", "no-cache");
	response.setDateHeader("Expires", 0);

	BufferedImage image = CheckCode.creatImage(request, response);

	ImageIO.write(image, "JPEG", response.getOutputStream());
	
	out.clear();
	out = pageContext.pushBody();
%>

CheckCode

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.Random;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class CheckCode
{
  public static BufferedImage creatImage(HttpServletRequest request, HttpServletResponse response)
  {
    int width = 130; int height = 50;

    Random random = new Random();
    BufferedImage image = new BufferedImage(width, height, 
      1);

    Graphics g = image.getGraphics();

    g.fillRect(0, 0, width, height);

    g.setFont(new Font("宋体", 1, 40));

    String str1 = randomStr(4);
    HttpSession session = request.getSession();
    session.setAttribute("rand", str1);
    g.drawString("    ", 0, 0);
    for (int i = 0; i < 4; ++i) {
      String rand = str1.substring(i, i + 1);

      g.setColor(
        new Color(20 + random.nextInt(110), 100 + random.nextInt(110), 
        20 + random.nextInt(110)));

      g.drawString(rand, 25 * i + 20, 40);
    }

    g.dispose();
    return image;
  }

  private static String randomStr(int n)
  {
    String str1 = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
    String str2 = "";
    int len = str1.length() - 1;

    for (int i = 0; i < n; ++i) {
      double r = Math.random() * len;
      str2 = str2 + str1.charAt((int)r);
    }
    return str2;
  }
}

 

转载于:https://my.oschina.net/beborn/blog/834081