一、使用纯Servlet实现验证码

(1)在web.xml配置:

<servlet>         <servlet-name>image</servlet-name>         <servlet-class>org.test.web.AuthImage</servlet-class>     </servlet>         <servlet-mapping>         <servlet-name>image</servlet-name>      <url-pattern>/authImage</url-pattern>     </servlet-mapping>  

(2)servlet源码

public class AuthImage extends HttpServlet     {             private static final String CONTENT_TYPE = "text/html; charset=gb2312";         //设置字母的大小,大小         private Font mFont = new Font("Times New Roman", Font.PLAIN, 17);         public void init() throws ServletException         {             super.init();         }         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);         }             public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException         {             response.setHeader("Pragma","No-cache");             response.setHeader("Cache-Control","no-cache");             response.setDateHeader("Expires", 0);             //表明生成的响应是图片             response.setContentType("image/jpeg");                          int width=100, height=18;             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(1, 1, width-1, height-1);             g.setColor(new Color(102,102,102));             g.drawRect(0, 0, width-1, height-1);             g.setFont(mFont);                 g.setColor(getRandColor(160,200));                 //画随机线             for (int i=0;i<155;i++)             {                 int x = random.nextInt(width - 1);                 int y = random.nextInt(height - 1);                 int xl = random.nextInt(6) + 1;                 int yl = random.nextInt(12) + 1;                 g.drawLine(x,y,x + xl,y + yl);             }                 //从另一方向画随机线             for (int i = 0;i < 70;i++)             {                 int x = random.nextInt(width - 1);                 int y = random.nextInt(height - 1);                 int xl = random.nextInt(12) + 1;                 int yl = random.nextInt(6) + 1;                 g.drawLine(x,y,x - xl,y - yl);             }                 //生成随机数,并将随机数字转换为字母             String sRand="";             for (int i=0;i<6;i++)             {                 int itmp = random.nextInt(26) + 65;                 char ctmp = (char)itmp;                 sRand += String.valueOf(ctmp);                 g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));                 g.drawString(String.valueOf(ctmp),15*i+10,16);             }                 HttpSession session = request.getSession(true);             session.setAttribute("rand",sRand);             g.dispose();             ImageIO.write(image, "JPEG", response.getOutputStream());         }         public void destroy()         {         }     }  

(3)页面显示

<img src="authImage"/> 

二、使用纯jsp实现验证码

<%@ page language="java" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"        contentType="image/jpeg" pageEncoding="UTF-8"%>      <%  //设置页面不缓存     response.setHeader("Pragma","No-cache");     response.setHeader("Cahce-Control","no-cache");     response.setDateHeader("Expires",0);     //在内存中创建图片     int width=60,height=20;     BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);     //获取图形上下文     Graphics g= image.getGraphics();     //生成随机类     Random random= new Random();     //设置背景颜色     g.setColor(new Color(160,200,100));     g.fillRect(0,0,width,height);     //设置字体     g.setFont(new Font("Times New Roman",Font.PLAIN,18));     //随机产生50条干扰线，使图形中的验证码不易被其他的程序探测到      g.setColor(new Color(160,200,200));     for(int i=0;i<50;i++)     {       int x=random.nextInt(width);       int y=random.nextInt(height);       int x1=random.nextInt(width);       int y1=random.nextInt(height);       g.drawLine(x,y,x+x1,y+y1);     }     //随机产生验证码（6位数字）     String sRand="";     for(int i=0;i<6;i++)     {       String rand=String.valueOf(random.nextInt(10));       sRand+=rand;       //将验证码显示到图象       g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));       g.drawString(rand,13*i+6,16);     }     session.setAttribute("rand",sRand);  //////将产生的验证码存储到sesson中     g.dispose();     ImageIO.write(image,"JPEG",response.getOutputStream());     out.clear(); //***********     out=pageContext.pushBody();//**********   %>

三、使用Struts2来实现验证码

(1)定义一个生成验证码的工具类

package com.cn.hospital.util;    import java.awt.Color;     import java.awt.Font;     import java.awt.Graphics;     import java.awt.image.BufferedImage;     import java.io.ByteArrayInputStream;     import java.io.ByteArrayOutputStream;     import java.util.Random;     import javax.imageio.ImageIO;     import javax.imageio.stream.ImageOutputStream;       public class RandomNumUtil {     private ByteArrayInputStream image;//图像       private String str;//验证码            private RandomNumUtil(){       init();//初始化属性       }       /*      * 取得RandomNumUtil实例      */       public static RandomNumUtil Instance(){       return new RandomNumUtil();       }       /*      * 取得验证码图片      */       public ByteArrayInputStream getImage(){       return this.image;       }       /*      * 取得图片的验证码      */       public String getString(){       return this.str;       }            private void init() {       // 在内存中创建图象       int width=85, height=20;       BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);       // 获取图形上下文       Graphics g = image.getGraphics();       // 生成随机类       Random random = new Random();       // 设定背景色       g.setColor(getRandColor(200,250));       g.fillRect(0, 0, width, height);       // 设定字体       g.setFont(new Font("Times New Roman",Font.PLAIN,18));       // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到       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);       }       // 取随机产生的认证码(6位数字)       String sRand="";       for (int i=0;i<6;i++){       String rand=String.valueOf(random.nextInt(10));       sRand+=rand;       // 将认证码显示到图象中       g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));       // 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成       g.drawString(rand,13*i+6,16);       }      //赋值验证码      this.str=sRand;            //图象生效       g.dispose();       ByteArrayInputStream input=null;       ByteArrayOutputStream output = new ByteArrayOutputStream();       try{       ImageOutputStream imageOut = ImageIO.createImageOutputStream(output);       ImageIO.write(image, "JPEG", imageOut);       imageOut.close();       input = new ByteArrayInputStream(output.toByteArray());       }catch(Exception e){       System.out.println("验证码图片产生出现错误："+e.toString());       }            this.image=input;/* 赋值图像 */       }       /*      * 给定范围获得随机颜色      */       private 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);       }     }

(2)定义一个验证码输出的action

package com.cn.hospital.action;    import java.io.ByteArrayInputStream;  import java.io.ByteArrayOutputStream;    import org.springframework.context.annotation.Scope;  import org.springframework.stereotype.Controller;    import com.cn.hospital.util.RandomCharUtil;  import com.cn.hospital.util.RandomNumUtil;  import com.opensymphony.xwork2.ActionContext;  import com.opensymphony.xwork2.ActionSupport;    @Controller("utilAction")  @Scope("prototype")  public class UtilAction extends ActionSupport{      private static final long serialVersionUID = -7193209177116825032L;   private ByteArrayInputStream inputStream;       private int width;         private int height;         private int fontSize;         private int codeLength;       private int disturbType;      public String validNumGenerate() throws Exception{    RandomNumUtil rdnu=RandomNumUtil.Instance();        this.setInputStream(rdnu.getImage());//取得带有随机字符串的图片        ActionContext.getContext().getSession().put("random", rdnu.getString());//取得随机字符串放入HttpSession        return SUCCESS;       }          public void setInputStream(ByteArrayInputStream inputStream) {        this.inputStream = inputStream;       }         public ByteArrayInputStream getInputStream() {        return inputStream;       }       }

(3)struts.xml配置

<!-- 产生随机验证码 -->    <action name="randNum" class="utilAction" method="validNumGenerate">                <result name="success" type="stream">                     <param name="contentType">image/jpeg</param>                     <param name="inputName">inputStream</param>                </result>          </action> 

四、小结

    对于java的web技术，归根究底还是在服务器端执行的servlet.从上面的三种不同实现中，我们很容易察觉到他们存在一个共同点，那就是返回浏览器端的contentType。

    servlet:使用response.setContentType(" ");方法来实现

    jsp:在<@ page contentType=" ">中来实现

    struts2:通过配置<param name="contentType"> </param>来实现

至于验证码的产生其实比较简单，在这里就不深究了。就此一点小感想，与同行共勉。