利用java实现验证码

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利用servlet实现java验证码：

产生一张图片

package com;import java.awt.Color;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.IOException;import java.io.PrintWriter;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 CreateImage extends HttpServlet {/*  生成一张图片 * (non-Javadoc) * @see javax.servlet.http.HttpServlet#doGet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse) */public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {     BufferedImage bi = new BufferedImage(68,22,BufferedImage.TYPE_INT_RGB);   Graphics g= bi.getGraphics();   Color c=new Color(200,150,255);   g.setColor(c);   g.fillRect(0, 0, 68, 22);    char ch[] ="QWERTYUIOPASDFGHJKLZXCVBNM0123456789".toCharArray();    int len=ch.length;    int index;    Random r = new Random();    StringBuffer sb=new StringBuffer();    for(int i=0;i<4;i++){    index=r.nextInt(len);    g.setColor(new Color(r.nextInt(88),r.nextInt(188),r.nextInt(255)));    //把字符串传到图片指定位置    g.drawString(ch[index]+" ", (i*15)+3, 18);    //为加入到session中做准备    sb.append(ch[index]);    }    request.getSession().setAttribute("piccode", sb.toString());    ImageIO.write(bi, "JPG", response.getOutputStream());}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {   doGet(request,response);}}

index.jsp

<script type="text/javascript">//在url末尾加一段数据告诉服务器这不是同一个请求   function flushimage(){   var time=new Date();        document.getElementById("image").src="<%=request.getContextPath()%>/servlet/CreateImage?id="+time;           }</script>  </head>          <body>   <form action="<%=request.getContextPath()%>/servlet/loginServlet" method="get">   验证码：<input  type="text" value="" name="checkcode"/>       <img alt="验证码" id="image" src="<%=request.getContextPath()%>/servlet/CreateImage">       <a href="javascript:flushimage()" >看不清楚</a><br>       <input type="submit" value="提交"/>             </form>   </body>

校验servlet

package com;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class loginServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setContentType("text/html;charset=utf-8");PrintWriter out = response.getWriter(); String checkcode= request.getParameter("checkcode"); checkcode=checkcode.toUpperCase(); String piccode=(String) request.getSession().getAttribute("piccode"); if(checkcode.equals(piccode)){ out.println("验证通过"); } else{ out.println("验证失败"); }out.flush();out.close();}}

web.xml:

<?xml version="1.0" encoding="UTF-8"?><web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">  <display-name></display-name>  <servlet>    <description>This is the description of my J2EE component</description>    <display-name>This is the display name of my J2EE component</display-name>    <servlet-name>CreateImage</servlet-name>    <servlet-class>com.CreateImage</servlet-class>  </servlet>  <servlet>    <description>This is the description of my J2EE component</description>    <display-name>This is the display name of my J2EE component</display-name>    <servlet-name>loginServlet</servlet-name>    <servlet-class>com.loginServlet</servlet-class>  </servlet>  <servlet-mapping>    <servlet-name>CreateImage</servlet-name>    <url-pattern>/servlet/CreateImage</url-pattern>  </servlet-mapping>  <servlet-mapping>    <servlet-name>loginServlet</servlet-name>    <url-pattern>/servlet/loginServlet</url-pattern>  </servlet-mapping>  <welcome-file-list>    <welcome-file>index.jsp</welcome-file>  </welcome-file-list></web-app>

这里面有如何利用开源组件kaptcha实现验证码的实例
http://blog.csdn.net/rocky_03/article/details/52145280

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