java servlet 实现验证码
servlet 代码：
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.Random;
import java.awt.*;
import java.awt.image.*;
import javax.imageio.*;
import javax.jms.Session;
public class SafeCode extends HttpServlet {
//产生随即的字体
private Font getFont() {
Random random = new Random();
Font font[] = new Font[5];
font[0] = new Font("Ravie", Font.PLAIN, 24);
font[1] = new Font("Antique Olive Compact", Font.PLAIN, 24);
font[2] = new Font("Forte", Font.PLAIN, 24);
font[3] = new Font("Wide Latin", Font.PLAIN, 24);
font[4] = new Font("Gill Sans Ultra Bold", Font.PLAIN, 24);
return font[random.nextInt(5)];
}
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
// 设置响应头 Content-type类型
resp.setContentType("image/jpeg");
// 以下三句是用于设置页面不缓存
resp.setHeader("Pragma", "No-cache");
resp.setHeader("Cache-Control", "No-cache");
resp.setDateHeader("Expires", 0);
OutputStream os = resp.getOutputStream();
int width = 83, height = 30;
// 建立指定宽、高和BufferedImage对象
BufferedImage image = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics(); // 该画笔画在image上
Color c = g.getColor(); // 保存当前画笔的颜色，用完画笔后要回复现场
g.fillRect(0, 0, width, height);
char[] ch = "abcdefghjkmnpqrstuvwxyz23456789".toCharArray(); // 随即产生的字符串 不包括 i l(小写L) o（小写O） 1（数字1）0(数字0)
int length = ch.length; // 随即字符串的长度
String sRand = ""; // 保存随即产生的字符串
Random random = new Random();
for (int i = 0; i < 4; i++) {
// 设置字体
g.setFont(getFont());
// 随即生成0-9的数字
String rand = new Character(ch[random.nextInt(length)]).toString();
sRand += rand;
// 设置随机颜色
g.setColor(new Color(random.nextInt(255), random.nextInt(255), random.nextInt(255)));
g.drawString(rand, 20 * i + 6, 25);
}
//产生随即干扰点
for (int i = 0; i < 20; i++) {
int x1 = random.nextInt(width);
int y1 = random.nextInt(height);
g.drawOval(x1, y1, 2, 2);
}
g.setColor(c); // 将画笔的颜色再设置回去
g.dispose();
//将验证码记录到session
req.getSession().setAttribute("safecode", sRand);
// 输出图像到页面
ImageIO.write(image, "JPEG", os);
}
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
doGet(req, resp);
}
}
xml 代码：
<servlet> <servlet-name>code</servlet-name> <servlet-class>SafeCode</servlet-class> </servlet> <servlet-mapping> <servlet-name>code</servlet-name> <url-pattern>/servlet/safecode</url-pattern> </servlet-mapping>
jsp代码：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8" %>
<%
String action = request.getParameter("action");
String safecodeText = request.getParameter("safecodeTest");
if("action".equals(action)){
String safecode = (String)session.getAttribute("safecode");
if(safecode.equals(safecodeText)){
out.print("验证码正确！");
}else{
out.print("验证码错误！请重新输入！");
}
}
%>
<html>
<head>
<title>验证码测试</title>
</head>
<body>
<form action="index.jsp" method="post">
<input type="hidden" name="action" value="action"/>
<img alt="验证码" src="servlet/safecode">
<input type="text" name="safecodeTest">
<input type="submit" value="go">
</form>
</body>
</html>