JAVA验证码

Servlet验证码：

画出验证码并发送到前台页面

package com.lxs.servlet;import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.IOException;import java.io.OutputStream;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 CodeServlet extends HttpServlet {    private static final long serialVersionUID = 1L;    protected void service(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        String codes="abcdefghijklmnopqrstuvwxyzABCDEFJHIJKLMNOPQRSTUVWXYZ0123456789";          BufferedImage img=new BufferedImage(80,30,BufferedImage.TYPE_3BYTE_BGR);        Graphics g=img.getGraphics();        //填充图片        g.setColor(new Color(255,255,255));        g.fillRect(0, 0, 80, 30);        //画入五个随机数        Random rm=new Random();        StringBuffer sb=new StringBuffer();        for(int i=0;i<5;i++){            int index=rm.nextInt(codes.length());            char code=codes.charAt(index);            g.setColor(new Color(rm.nextInt(256),rm.nextInt(256),rm.nextInt(256)));            g.setFont(new Font("宋体", Font.BOLD, 25));            g.drawString(code+"", 2+15*i, 22);            sb.append(code);        }        //画干扰线        for(int i=0;i<10;i++){            g.setColor(new Color(rm.nextInt(256),rm.nextInt(256),rm.nextInt(256)));            g.drawLine(rm.nextInt(100), rm.nextInt(50), rm.nextInt(100), rm.nextInt(50));        }        //将验证码图片回写给浏览器        response.setContentType("image/jpeg;charset=utf-8");        OutputStream out=response.getOutputStream();        ImageIO.write(img, "jpeg", out);        //将随机字符串保存在session中        request.getSession().setAttribute("code", sb.toString());    }}

配置web.xml

<servlet-name>CodeServlet</servlet-name>    <servlet-class>com.yinhe.web.servlet.CodeServlet</servlet-class>  </servlet>  <servlet-mapping>    <servlet-name>CodeServlet</servlet-name>    <url-pattern>/checkCode</url-pattern>  </servlet-mapping>

前台显示验证码

<img src="checkCode" alt="" id="codeImg"style="width: 80px; height: 30px; border: 1px solid black;" /> <a href="javascript:;" onclick="document.getElementById('codeImg').src = 'checkCode?'+(new Date()).getTime()">换一张</a><span id="codemsg" style="color: red; font-size: 20px;"></span>

JSP验证码

画出验证码 写如session域中

<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" pageEncoding="utf-8"%><%!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();                           /*这句针对resin服务器，如果是tomacat可以不要这句*/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);}// 将认证码存入SESSIONsession.setAttribute("sRand",sRand);g.dispose();ImageIO.write(image, "JPEG", response.getOutputStream());%>

前台调用时使用的代码

<script type="text/javascript">         function loadImage(){         document.getElementById("randImage").src = "${pageContext.request.contextPath}/image.jsp?"+Math.random(); //Math.random()方法非常重要，它使每次的请求都不同以便重新发送。如果每次的请求都一样，那么不会重新生成页面         }      </script><img onClick="javascript:loadImage();"  title="换一张试试" id="randImage"                           src="${pageContext.request.contextPath}/image.jsp"  border="1" >