Web 开发实现验证码输入功能

首先建一个类生成一个验证码的图片代码如下

 

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics2D;

import java.awt.image.BufferedImage;

import java.io.IOException;

import java.io.OutputStream;

import java.util.Random;

 

import javax.imageio.ImageIO;

 

public class MakeSecurityPic {

       

       /**

        * 生成验证码的字符数字组合

        */

       private char[] mapTable = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i',

                     'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',

                     'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8',

                     '9' };

 

       /**

        * 获取验证码图片

        * 

        * @param width

        *            图片的宽

        * @param height

        *            图片的高

        * @param os

        *            输出流

        * @return

        */

       public String getSecurityPic(Integer width, Integer height, OutputStream os) {

 

              if (width == 0)

                     width = 60;

              if (height == 0)

                     height = 20;

 

              BufferedImage image = new BufferedImage(width, height,

                            BufferedImage.TYPE_INT_RGB);

 

              //

              Graphics2D g = image.createGraphics();

 

              // 填充背景色

              g.setColor(Color.white);

              g.fillRect(0, 0, width, height);

 

              // 绘制边框

              g.setColor(Color.BLACK);

              g.drawRect(0, 0, width - 1, height - 1);

 

              // 验证码

              String security = "";

 

              // 随机生成验证码

              Random random = new Random();

              for (int i = 0; i < 4; i++) {

                     security += mapTable[random.nextInt(mapTable.length)];

              }

 

              // 绘制验证码

              g.setColor(Color.BLACK);

              g.setFont(new Font("MS Sans Serif", Font.PLAIN, 18));

 

              String temp = security.substring(0, 1);

              g.drawString(temp, 7, 15);

              temp = security.substring(1, 2);

              g.drawString(temp, 18, 17);

              temp = security.substring(2, 3);

              g.drawString(temp, 28, 18);

              temp = security.substring(3, 4);

              g.drawString(temp, 40, 17);

 

              // 绘制干扰点

              g.setColor(Color.BLACK);

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

                     g.drawOval(random.nextInt(width), random.nextInt(height), 0, 0);

              }

              // 释放资源

              g.dispose();

 

              try {

                     // 输出图片到缓冲区

                     ImageIO.write(image, "JPG", os);

              } catch (IOException e) {

                     // TODO Auto-generated catch block

                     e.printStackTrace();

              }

              return security;

       }

}

 

 

 

再建一个servlet 类型为

 

response.setContentType("image/jpg");

是一个图片类型的。

代码如下：

package com.security;

 

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 MakeSecurityServlet extends HttpServlet {

 

 

       public void doGet(HttpServletRequest request, HttpServletResponse response)

                     throws ServletException, IOException {

              doPost(request,response);

       }

 

 

       public void doPost(HttpServletRequest request, HttpServletResponse response)

                     throws ServletException, IOException {

              

              response.setContentType("image/jpg");

              MakeSecurityPic msp = new MakeSecurityPic();

              String security = msp.getSecurityPic(0, 0, response.getOutputStream());

              

              request.getSession().setAttribute("security", security);

       }

 

}

 

 

显示到jsp页面上如下：

       security:<input type="text" name="security"/><img id="securityPic" src="servlet/MakeSecurityServlet"><a href="#" onClick="reloadSecurityPic()">看不清楚，换一个</a><br>