生成图片验证码
1,定义生成图片验证码的servlet，package com.test.demo;import java.awt.Color;import java.awt.Font;import java.awt.Graphics2D;import java.awt.image.BufferedImage;import java.io.IOException;import java.util.Random;import javax.servlet.ServletException;import javax.servlet.ServletOutputStream;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.sun.image.codec.jpeg.JPEGCodec;import com.sun.image.codec.jpeg.JPEGImageEncoder;public class RandCode extends HttpServlet {protected static Random random=new Random();protected void doGet(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {// TODO Auto-generated method stubdoPost(req,resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {// TODO Auto-generated method stubreq.setCharacterEncoding("utf-8");resp.setCharacterEncoding("utf-8");resp.setContentType("image/jpeg"); //设置输出类型为jpeg图片int width=70;int height=25; //验证图片的宽度，高度Color back=getBack();Color front=getFront(back);String code=getString();req.getSession().setAttribute("rand", code);//保存到session里面 BufferedImage bi=new BufferedImage(width,height,BufferedImage.TYPE_INT_BGR); Graphics2D g=bi.createGraphics(); //得到画布 g.setFont(new Font(Font.SANS_SERIF,Font.BOLD,20));//设置字体 g.setColor(back); g.fillRect(0, 0, width, height); //画背景 g.setColor(front); g.drawString(code,18,20); //画字符 for(int i=0,n=random.nextInt(20);i<n;i++){ g.fillRect(random.nextInt(width),random.nextInt(height),1,1); } //产生至多20个噪点 ServletOutputStream so=resp.getOutputStream();//得到二进制输出流 JPEGImageEncoder je=JPEGCodec.createJPEGEncoder(so); //对图片进行编码成jpeg格式 je.encode(bi); so.flush(); //刷新缓存}/** * @desc 得到图片背景色 * @author aj * @date 2011-3-30 * */protected static Color getBack(){return new Color(random.nextInt(255),random.nextInt(255),random.nextInt(255));}/** * @desc 生成颜色的反色 * @author aj * @date 2011-3-30 * */protected static Color getFront(Color c){return new Color(255-c.getRed(),255-c.getGreen(),255-c.getBlue());}/** * @desc 产生随机字符 * @author aj * @date 2011-3-30 * */protected static String getString(){String old="23456789abcdefghijkmnpqrstuvwxyz"; //验证图片上面的随机字符StringBuffer sb=new StringBuffer();int j=0;for(int i=0;i<4;i++){j=random.nextInt(old.length());sb.append(old.substring(j,j+1));} return sb.toString();} } 2，定义jsp文件，使用验证码并通过按钮切换验证码；
<%@ 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>Insert title here</title> <script type="text/javascript"> function change(){document.getElementById("code").src="Rand?sc="+new Date().getTime(); }; </script></head><body><div> <span><img src="Rand" id="code"/><button id="btn" style="margin-left:12px;" >看不清</button></span></div></body></html>
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