image.jsp-------------------生成隨即驗證碼圖片的jsp頁面
代碼如下：
<%@ page contentType="image/jpeg" import="java.awt.*,
java.awt.image.*,java.util.*,javax.imageio.*" %>
<%!
Color getRandColor(int fc,int bc)
{
?Random random = new Random();
?if(fc>255) fc=255;
?if(bc>255) bc=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);
}
%>
<%
out.clear();//這句針對resin服務器，如果是tomacat可以不要這句
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);
int width=60, height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
Random random = new Random();
g.setColor(getRandColor(200,250));
g.fillRect(0, 0, width, height);
g.setFont(new Font("Times New Roman",Font.PLAIN,18));
?
g.setColor(getRandColor(160,200));
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);
}
String sRand="";
for (int i=0;i<4;i++){
String rand=String.valueOf(random.nextInt(10));
sRand+=rand;
g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
g.drawString(rand,13*i+6,16);
}
// 將認證碼存入SESSION
session.setAttribute("rand",sRand);
g.dispose();
ImageIO.write(image, "JPEG", response.getOutputStream());
%>
login.jsp--------------------登錄頁面，在這里我是提供輸入驗證碼然后提交進行驗證
代碼如下：
<%@ page language="java" import="java.sql.*" errorPage="" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>用戶登錄</title>
<script language="javascript">
? function loadimage(){
??? document.getElementById("randImage").src = "image.jsp?"+Math.random();
? }
? </script>
</head>
<body>
<table width="256" border="0" cellpadding="0" cellspacing="0">
? <!--DWLayoutTable-->
? <form action="validate.jsp" method="post" name="loginForm">
? <tr>
??? <td width="118" height="22" valign="middle" align="center"><input type="text" name="rand" size="15"></td>
??? <td width="138" valign="middle" align="center"><img alt="code..." name="randImage" id="randImage" src="image.jsp" width="60" height="20" border="1" align="absmiddle"></td>
? </tr>
? <tr>
??? <td height="36" colspan="2" align="center" valign="middle"><a href="javascript:loadimage();"><font class=pt95>看不清點我</font></a></td>
? </tr>
? <tr>
??? <td height="36" colspan="2" align="center" valign="middle"><input type="submit" name="login" value="提交"></td>
? </tr>
? </form>
</table>
</body>
</html>
validate.jsp-------------用來驗證輸入的驗證碼是否正確
代碼如下：
<%@ page contentType="text/html; charset=gb2312" language="java" import="java.sql.*" errorPage="" %>
<%
String rand = (String)session.getAttribute("rand");
String input = request.getParameter("rand");
if(rand.equals(input)){
?out.print("<script>alert('驗證通過！');</script>");
} else{
?out.print("<script>alert('請輸入正確的驗證碼！');location.href='login.jsp';</script>");
}
%>
上面生成的是純數字的驗證碼，我們對其進行一下修改就可以生成數字字母混合的驗證碼了。
修改部分的代碼如下：
<%
......
......
......
for (int i=0;i<155;i++)
{
? ......
? ......
}
//-----------------以下是要添加的代碼--------------
char c[] = new char[62];
for (int i = 97, j = 0; i < 123; i++, j++) {
c[j] = (char) i;
}
for (int o = 65, p = 26; o < 91; o++, p++) {
c[p] = (char) o;
}
for (int m = 48, n = 52; m < 58; m++, n++) {
c[n] = (char) m;
}???????
String sRand="";
for (int i=0;i<4;i++){
int x = random.nextInt(62);
String rand=String.valueOf(c[x]);
sRand+=rand;
//---------------------------------------------
%>
據有部分朋友反應，在測試過程中出現java.lang.IllegalStateException: getOutputStream() has already been called for this response的異常，經過測試發現，使用tomcat5一下的版本確實會出現該問題，解決的辦法就是把tomcat換成高點版本就可以了。