Java 验证码，

来源： javaer 分享于 2025-02-27 点击 46988 次点评：269

Java 验证码，

下面的例子是用Servlet生成的一个验证码，例子是模拟登陆。

login.jsp

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>验证码</title>
</head>
<body>
	<form action="${pageContext.request.contextPath }/servlet/LoginServlet">
	<table border="0" cellspacing="0" cellpadding="0" width="50%">
		<tr>
			<td width="20%" align="right">用户名：</td><td colspan="2"><input type="text" name="username" value="" size="34"/></td>
		</tr>
		<tr>
			<td width="20%" align="right">密 码：</td><td colspan="2"><input type="password" name="password" value="" size="35"/></td>
		</tr>
		<tr>
			<td width="20%" align="right">验证码：</td><td width="21%"><input type="text" name="code" value="" size="15"/></td><td align="left"><img src="${pageContext.request.contextPath }/servlet/ImageCodeMakerServlet" width="100px" height="30" /></td>
		</tr>
	</table>
	</form>
</body>
</html>

在web.xml中

<servlet>
  	<servlet-name>login</servlet-name>
  	<servlet-class>com.web.LoginServlet</servlet-class>
  </servlet>
  <servlet>
  	<servlet-name>imageCodeMakerServlet</servlet-name>
  	<servlet-class>com.web.ImageCodeMakerServlet</servlet-class>
  </servlet>
  <servlet-mapping>
  	<servlet-name>login</servlet-name>
  	<url-pattern>/servlet/LoginServlet</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
	<servlet-name>imageCodeMakerServlet</servlet-name>
	<url-pattern>/servlet/ImageCodeMakerServlet</url-pattern>
  </servlet-mapping>

在后台Servlet里

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class LoginServlet extends HttpServlet{

	@Override
	protected void service(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		String username = request.getParameter("username");
		String password = request.getParameter("password");
		String code = request.getParameter("code");// 页面，用户输入的验证码
		
		HttpSession session = request.getSession();
		String randCode = (String)session.getAttribute("randCode");// 得到系统生成的验证码
		
		if(randCode.equals(code)){// 验证码输入正确
			System.out.println("验证码输入正确");
		}else{
			System.out.println("验证码不正确");
		}
	}
}

ImageCodeMakerServlet如下

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ImageCodeMakerServlet extends HttpServlet {

	public ImageCodeMakerServlet() {
		super();
	}

	public void destroy() {
		super.destroy(); 
	}

	public void service(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		// 首先设置页面不缓存
		response.setHeader("Pragma", "No-cache");
		response.setHeader("Cache-Control", "no-cache");
		response.setDateHeader("Expires", 0);

		// 定义图片的宽度和高度
		int width = 90, height = 40;
		// 创建一个图像对象
		BufferedImage image = new BufferedImage(width, height,
				BufferedImage.TYPE_INT_RGB);
		// 得到图像的环境对象
		Graphics g = image.createGraphics();

		Random random = new Random();
		// 用随机颜色填充图像背景
		g.setColor(getRandColor(180, 250));
		g.fillRect(0, 0, width, height);
		for (int i = 0; i < 5; i++) {
			g.setColor(getRandColor(50, 100));
			int x = random.nextInt(width);
			int y = random.nextInt(height);
			g.drawOval(x, y, 4, 4);
		}
		// 设置字体，下面准备画随机数
		g.setFont(new Font("", Font.PLAIN, 40));
		// 随机数字符串
		String sRand = "";
		for (int i = 0; i < 4; i++) {
			// 生成四个数字字符
			String rand = String.valueOf(random.nextInt(10));
			sRand += rand;
			// 生成随机颜色
			g.setColor(new Color(20 + random.nextInt(80), 20 + random
					.nextInt(100), 20 + random.nextInt(90)));
			// 将随机数字画在图像上
			g.drawString(rand, (17 + random.nextInt(3)) * i + 8, 34);

			// 生成干扰线
			for (int k = 0; k < 12; k++) {
				int x = random.nextInt(width);
				int y = random.nextInt(height);
				int xl = random.nextInt(9);
				int yl = random.nextInt(9);
				g.drawLine(x, y, x + xl, y + yl);
			}
		}

		// 将生成的随机数字字符串写入Session
		request.getSession(false).setAttribute("randcode", sRand);
		// 使图像生效
		g.dispose();
		// 输出图像到页面
		ImageIO.write(image, "JPEG", response.getOutputStream());
	}

	/**
	 * Initialization of the servlet. <br>
	 * 
	 * @throws ServletException
	 *             if an error occurs
	 */
	public void init() throws ServletException {
		// Put your code here
	}
	/**
	 * 产生一个随机的颜色
	 * 
	 * @param fc
	 *            颜色分量最小值
	 * @param bc
	 *            颜色分量最大值
	 * @return
	 */
	public 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);
	}

}

Java 验证码，

Java 验证码，

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