Servlet实现的验证码功能

来源：互联网发布：mac 复制黏贴快捷键编辑：程序博客网时间：2024/05/20 23:35

首先servet中实现产生验证码的功能

package com.filter;import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.ServletOutputStream;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;import com.sun.image.codec.jpeg.JPEGCodec;import com.sun.image.codec.jpeg.JPEGImageEncoder;@WebServlet("/image.do")public class ImageCodeServlet extends HttpServlet {private static final long serialVersionUID = 1L;protected void processRequest(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {       response.setContentType("image/jpeg"); // 通知服务器按图片的方式接受浏览器发送的东西       HttpSession session = request.getSession();       // 验证码图片的高度和宽度       int width = 60;       int height = 20;       StringBuffer randbuffer = new StringBuffer();       //禁止图片缓存       response.setHeader("Pragma", "No-cache");       response.setHeader("Cache-Control", "no-cache");       response.setDateHeader("Expires", 0);       BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);       Graphics g = image.getGraphics(); //获取image画笔       String chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"; // 从中选择随机数       char[] rands = new char[4];       //从chars字符串中随机选择四个字符保存在数组中       for(int i = 0; i < 4; i++) {       int rand = (int) (Math.random() * 36);       rands[i] = chars.charAt(rand);       randbuffer.append(rands[i]);       }       session.setAttribute("randString", randbuffer.toString()); // 把验证码存在session中用以验证       System.out.println(session.getAttribute("randString"));       //设置画笔颜色并用画笔填充矩形，左上角（0，0）       g.setColor(new Color(0xDCDCDC));       g.fillRect(0, 0, width, height);       // 划120个小圆点       for(int i = 0; i < 120; i++) {       int x = (int)(Math.random() * width);       int y = (int)(Math.random() * height);       int red = (int)(Math.random() * 255); //随机产生三色，使得小圆点颜色不一样       int green = (int)(Math.random() * 255);       int blue = (int)(Math.random() * 255);       g.setColor(new Color(red, green, blue));       g.drawOval(x, y, 1, 0);       }       // 设置画笔的颜色和字体       g.setColor(Color.BLACK);       g.setFont(new Font(null, Font.ITALIC|Font.BOLD, 18));       //画四个字符       g.drawString("" + rands[0], 1, 17);       g.drawString("" + rands[1], 16, 15);       g.drawString("" + rands[2], 31, 18);       g.drawString("" + rands[3], 46, 16);       g.dispose();       ServletOutputStream out = response.getOutputStream();       JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);       encoder.encode(image);       out.flush();           }    protected void doGet(HttpServletRequest request, HttpServletResponse response)    throws ServletException, IOException {        processRequest(request, response);    }    protected void doPost(HttpServletRequest request, HttpServletResponse response)    throws ServletException, IOException {        processRequest(request, response);    }    public String getServletInfo() {        return "Short description";    }}

可以在上面的产生随机数中选择验证码字符多个，根据实际需要进行适当修改边框大小

然后是一个简单的login.jsp页面访问

<%@ page language="java" contentType="text/html; charset=utf-8"    pageEncoding="utf-8"%><html><head></head><body><form method="post" action="login.do"><img alt="image" src="image.do"/></form></body></html>