JavaEE 验证码的使用

package org.xawl.jsj;

 

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.io.IOException;

import java.util.Iterator;

 

import javax.imageio.IIOImage;

import javax.imageio.ImageIO;

import javax.imageio.ImageTypeSpecifier;

import javax.imageio.ImageWriteParam;

import javax.imageio.ImageWriter;

import javax.imageio.stream.ImageOutputStream;

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 ValidateCodeServlet extends HttpServlet {

       //将来存放验证码值的session的key值

       public static final String VALIDATE_CODE_KEY = "ValidateCode";

 

       //请求servlet的时的被调方法

       public void doGet(HttpServletRequest request, HttpServletResponse response)

                     throws ServletException, IOException {

 

//设置文档的内容类型为jpeg类型，

//从而在浏览的时候告知浏览器这是一个图片类型

response.setContentType("image/jpeg");

              //生成验证码，保存在session中

              HttpSession session = request.getSession();

             

//调用下面的generateString方法，

//生成一个4位长的每位为0-9的随机字符串

 

              String code = generateString();

              session.setAttribute(VALIDATE_CODE_KEY, code);

 

              //生出内存图片

              BufferedImage image = generateImage(code);

 

              //输出图片

              outputImage(image, response.getOutputStream());

       }

 

 

       //往页面输出的方法

       private void outputImage(BufferedImage image, ServletOutputStream out)

                     throws IOException {

              ImageWriter writer = null;

              //下面进行对图片格式的一些修改

              ImageTypeSpecifier type =

ImageTypeSpecifier.createFromRenderedImage(image);

              Iterator iter = ImageIO.getImageWriters(type, "jpg");

              if (iter.hasNext()) {

                     writer = (ImageWriter) iter.next();

              }

             

              IIOImage iioImage = new IIOImage(image, null, null);

              ImageWriteParam param = writer.getDefaultWriteParam();

 

              param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);

              //控制图片质量，1.0最高

              param.setCompressionQuality(1.0F);

              //创建输出流

              ImageOutputStream outputStream = ImageIO.createImageOutputStream(out);

              //将构建好的图片输出流写入到页面中

              writer.setOutput(outputStream);

              writer.write(null, iioImage, param);

       }

 

      

       //用来生成随机字符串的方法

private String generateString() {

              int a = (int) (Math.random() * 10);

              int b = (int) (Math.random() * 10);

              int c = (int) (Math.random() * 10);

              int d = (int) (Math.random() * 10);

              return "" + a + b + c + d;

       }

      

       //生成图片的方法

       private BufferedImage generateImage(String code) {

              //设置图片信息，宽，高，具有 8 位 RGB 颜色分量的图像

              BufferedImage image = new BufferedImage(100, 30,

                            BufferedImage.TYPE_INT_RGB);

              //得到画笔

              Graphics g = image.getGraphics();

              //产生背景图片

              g.setColor(Color.white);

              //画一个矩形框

              g.fillRect(1, 1, 98, 28);

              //添加一些干扰的线条

              for (int i = 0; i < 20; i++) {

                     g.setColor(generateColor());

                     int x1 = (int) (Math.random() * 100);

                     int y1 = (int) (Math.random() * 30);

                     int x2 = (int) (Math.random() * 100);

                     int y2 = (int) (Math.random() * 30);

                     g.drawLine(x1, y1, x2, y2);

              }

              //画数字

              //为了得到不同效果的随机字符串，这里采用一个一个字符串的画。

              //这样可以使其颜色或者其他信息有所不同

 

              g.setFont(new Font("IMPACT", Font.PLAIN,

                            20 + (int) (Math.random() * 10)));

              g.setColor(generateColor());

              g.drawString(code.charAt(0) + "", 5, 28);

 

              g.setFont(new Font("IMPACT", Font.PLAIN,

                            20 + (int) (Math.random() * 10)));

              g.setColor(generateColor());

              g.drawString(code.charAt(1) + "", 30, 28);

 

              g.setFont(new Font("IMPACT", Font.PLAIN,

                            20 + (int) (Math.random() * 10)));

              g.setColor(generateColor());

              g.drawString(code.charAt(2) + "", 55, 28);

 

              g.setFont(new Font("IMPACT", Font.PLAIN,

                            20 + (int) (Math.random() * 10)));

              g.setColor(generateColor());

              g.drawString(code.charAt(3) + "", 80, 28);

 

              return image;//返回制作好的图像

       }

      

       //生成随机的颜色

       private Color generateColor() {

              int r = (int) (Math.random() * 180);

              int g = (int) (Math.random() * 180);

              int b = (int) (Math.random() * 180);

              return new Color(r, g, b);

       }

}

 

Servlet在web.xml中的配置：

<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>ValidateCodeServlet</servlet-name>

    <servlet-class>org.xawl.jsj.ValidateCodeServlet</servlet-class>

  </servlet>

 

  <servlet-mapping>

    <servlet-name>ValidateCodeServlet</servlet-name>

    <url-pattern>/servlet/validatecode</url-pattern>

</servlet-mapping>

 

 页面代码

<%@ page language="java"  pageEncoding="gb2312" %>

 

 

<html>

  <head>

    <script type="text/javascript">

       function change(){

           var imgcode = document.getElementById("codeimg");

           imgcode.src="servlet/validatecode?"+new Date();

       }

    </script>

  </head>

  <body>

  <form action="check.jsp" method="post" >

    验证码:<img alt="" src="servlet/validatecode">    <a href="#" onclick="change();">点击更换</a> <br>

    <input type="text" name="code" >    <br>

    <input type="submit"  value="验证" >    <br>

   </form>

  </body>

</html>

 

 

 

接受提交页面：

页面代码：

<%@ page language="java"  pageEncoding="gb2312"%>

<%

String code = request.getParameter("code");

String value = session.getAttribute("ValidateCode").toString();

if(value.equals(code)){

    out.println("验证码正确");

}else{

    out.println("<font color=red>验证码不正确</font>");

}

%>