java生成图片验证码示例程序

复制代码 代码如下:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>

欢迎登陆本系统

 账号:

 密码:

 验证码:
 
   
 

复制代码 代码如下:

<%@page import="java.util.Random"%>
<%@page import="java.awt.Graphics"%>
<%@page import="javax.imageio.*"%>
<%@page import="java.awt.*"%>
<%@page import="java.awt.image.BufferedImage"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%
 final char[] str = {'0','1','2','3','4','5','6','7','8','9',
    'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q',
    'r','s','t','u','v','w','x','y','z','A','B','C','D','E','F','G','H',
    'I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
 int width=100,height=60;
 BufferedImage bi = new BufferedImage(width,height,
   BufferedImage.TYPE_INT_RGB);
 Graphics g = bi.getGraphics();
 g.setColor(new Color(200,200,200));
 g.fillRect(0, 0, width, height);
 Random rnd = new Random();
 StringBuffer sb = new StringBuffer("");
 //产生四位数的字母数字验证码，各个数字的颜色也随即
 for(int i=0; i<4; i++) {
  int num = rnd.nextInt(str.length);
  Color c = new Color(rnd.nextInt(256),
    rnd.nextInt(256),rnd.nextInt(256));
  g.setColor(c);
  g.setFont(new Font("", Font.BOLD+Font.ITALIC, 20));
  g.drawString(str[num]+"", 10, 17);
  sb.append(str[num]);
 }
 //划干扰线
 for(int i=0; i<10; i++) {
  Color c = new Color(rnd.nextInt(256),
    rnd.nextInt(256),rnd.nextInt(256));
  g.setColor(c);
  g.drawLine(rnd.nextInt(width), rnd.nextInt(height),
    rnd.nextInt(width), rnd.nextInt(height));
 }
 String s = new String(sb);
 /*
 若是产生四位数字，则nextInt(8999) + 1000;
 然后String.valueOf转换为String
 */
 //验证码存入session里，方便在登陆校检页比对
 session.setAttribute("image",s);
 //输出到页面
 ImageIO.write(bi,"JPEG",response.getOutputStream());
 /*
 加入下面这两句什么作用呢？
 否则报异常: java.lang.IllegalStateException: getOutputStream()
 has already been called for this response
 不管原因了
 */
 out.clear();
 out = pageContext.pushBody();

%>