Java图片验证码

一.准备知识

        随便一本JavaWeb书上都有，就那几步，看看就ok了，不过可能存在一些问题，路过的指教下。。。

二.代码

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

    pageEncoding="UTF-8"%>

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>登陆页面</title>

<script type="text/javascript">

	function refresh() {

		loginForm.image.src = "creatImage.jsp";

	}

</script>

</head>

<body>

<h1>欢迎登陆本系统</h1><br>

<form action="" method = "post" name="loginForm">

	<label>账号:<input name="username" type="text" /></label><br>

	<label>密码:<input name="password" type="password" /></label><br>

	<label>验证码:<input name="code" type="text" /></label>

	<!-- 将验证码当做图片处理 -->

    <img name="image" border="0" src="creatImage.jsp" onclick="refresh()" />

	<input type="submit" value="登陆" />

</form>

</body>

</html>



<%@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();

	

%>

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>图片生成</title>

</head>

<body>

</body>

</html>







            

            
posted @ 
2013-11-27 17:33 
加拿大小哥哥 
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