jsp生成验证码

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在Java中，java.awt和java.awt.image包提供了基本的绘制图像的能力，我们可以在内存中绘制好需要的图形，然后编码成jpeg或其他图像格式，最后发送相应给浏览器即可。下面是使用Servlet动态创建图像的详细步骤：

1．创建BufferedImage对象，该对象存在内存中，负责保存绘制的图像；
2．创建Graphics2D对象，该对象负责绘制所需的图像；
3．当绘制完成后，调用com.sun.image.codec.jpeg包的JPEG编码器对其编码；
4．最后将编码后的数据输出至HttpResponse即可。

注意com.sun.image.codec.jpeg包位于JDK目录的rt.jar包中，它不是公开的API，需要将rt.jar复制到web应用程序的WEB-INF/lib下。

我们先创建一个最简单的Servlet：

public class CreateImageServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException
    {
        response.setContentType("image/jpeg");
    }
}

我们首先设置了response的contentType为image/jpeg，这样浏览器就可以正确识别。

然后，创建一个大小为100x100的BufferedImage对象，准备绘图：

编码后的JPEG图像直接输出到了out对象中，我们只要传入response. getOutputStream()就可以直接输出到HttpResponse中。

下面是完整的代码：

package com.crackj2ee.web.util;

import java.io.*;
import java.awt.*;
import java.awt.image.*;

import javax.servlet.*;
import javax.servlet.http.*;

import com.sun.image.codec.jpeg.*;

/**
* @author Liao Xue Feng
*/
public class CreateImageServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException
    {
        response.setContentType("image/jpeg");
        createImage(response.getOutputStream());
    }

    private void createImage(OutputStream out) {
        int width = 100;
        int height = 100;
        BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics2D g = bi.createGraphics();
        // set background:
        g.setBackground(Color.BLUE);
        g.clearRect(0, 0, width, height);
        // set fore color:
        g.setColor(Color.RED);
        // start draw:
        g.drawLine(0, 0, 99, 199);
        // end draw:
        g.dispose();
        bi.flush();
        // encode:
        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
        JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(bi);
        param.setQuality(1.0f, false);
        encoder.setJPEGEncodeParam(param);
        try {
            encoder.encode(bi);
        }
        catch(IOException ioe) {
            ioe.printStackTrace();
        }
    }
}

最后将这个Servlet编译，注册到web.xml中，映射路径为/CreateImage，写一个简单的index.html测试：

<html><head></head>
<body>
<img src="CreateImage">
</body></html>

yeeku.web;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class AuthImg extends HttpServlet {

    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        response.setContentType("image/jpeg");
        response.setHeader("Pragma","No-cache");
        response.setHeader("Cache-Control","no-cache");
        response.setDateHeader("Expires", 0);
        HttpSession session=request.getSession();
        // 在内存中创建图象
        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.CreateGraphics();

//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));

        //画边框
        //g.setColor(new Color());
        //g.drawRect(0,0,width-1,height-1);

        // 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(4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(newColor(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);
        }

        // 将认证码存入SESSION
        session.setAttribute("rand",sRand);
        // 图象生效
        g.dispose();
        ServletOutputStream responseOutputStream =response.getOutputStream();
        // 输出图象到页面
        ImageIO.write(image, "JPEG", responseOutputStream);

        //以下关闭输入流！
        responseOutputStream.flush();
        responseOutputStream.close();
    }
    Color getRandColor(int fc,int bc){//给定范围获得随机颜色
        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);
    }
    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">

    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";
    }
    // </editor-fold>
}

//产生的验证码有字母的Servlet

public class AuthImg extends HttpServlet
{
    private Font mFont = new Font("Arial Black", Font.PLAIN, 16);
    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);
        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));
        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);
        }
        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);
        }

        String sRand="";
        for (int i=0;i<6;i++) {
   String tmp = getRandomChar();
            sRand += tmp;
            g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
         g.drawString(tmp,15*i+10,15);
        }

        HttpSession session = request.getSession(true);
        session.setAttribute("rand",sRand);
        g.dispose();
        ImageIO.write(image, "JPEG", response.getOutputStream());
    }
    private String getRandomChar()
    {
  int rand = (int)Math.round(Math.random() * 2);
  long itmp = 0;
  char ctmp = '/u0000';
  switch (rand)
  {
   case 1:
    itmp = Math.round(Math.random() * 25 + 65);
    ctmp = (char)itmp;
    return String.valueOf(ctmp);
   case 2:
    itmp = Math.round(Math.random() * 25 + 97);
    ctmp = (char)itmp;
    return String.valueOf(ctmp);
   default :
    itmp = Math.round(Math.random() * 9);
    return String.valueOf(itmp);
  }
    }

第二步,在工程中的web.xml中配置上面的servlet

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

   <servlet>
        <servlet-name>img</servlet-name>
        <servlet-class>org.yeeku.web.AuthImg</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>img</servlet-name>
     <url-pattern>/authImg</url-pattern>
    </servlet-mapping>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>

第三步,编写验证码显示的jsp页面:

<%@ page contentType="text/html;charset=gb2312"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
  <title>认证码输入页面</title>
  <meta http-equiv="Content-Type" content="text/html; charset=gb2312">
  <META HTTP-EQUIV="Pragma" CONTENT="no-cache">
  <META HTTP-EQUIV="Cache-Control" CONTENT="no-cache">
  <META HTTP-EQUIV="Expires" CONTENT="0">

</script>

</head>
<body>
  <form method=post action="check.jsp">
   <table>
    <tr>
     <td align=left>
      系统产生的认证码：
     </td>
     <td>
      <img border=0 src="authImg">  <input type="button" value="看不清，在换一张" onclick="myrefresh()">
     </td>
    </tr>
    <tr>
     <td align=left>
      输入上面的认证码：
     </td>
     <td>
      <input type=text name=rand maxlength=4 value="">
     </td>
    </tr>
    <tr>
     <td colspan=2 align=center>
      <input type=submit value="提交检测">
     </td>
    </tr>
    </table>
   </form>
</body>

第四步,编写jsp测试验证码

<%@ page contentType="text/html; charset=gb2312" language="java" import="java.sql.*" errorPage="" %>
<html>
<head>
<title>认证码验证页面</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
<META HTTP-EQUIV="Cache-Control" CONTENT="no-cache">
<META HTTP-EQUIV="Expires" CONTENT="0">
</head>

<body>
<%
String rand = (String)session.getAttribute("rand");
String input = request.getParameter("rand");
%>
系统产生的认证码为： <%= rand %><br>
您输入的认证码为： <%= input %><br>
<br>
<%
  if (rand.equals(input)) {
%>
<font color=green>输入相同，认证成功！</font>
<%
  } else {
%>
<font color=red>输入不同，认证失败！</font>
<%
  }
%>
</body>
</html>

[另服一例，类似上面]