javaweb開發(fā)之servlet圖形驗(yàn)證碼功能的實(shí)現(xiàn)

一驗(yàn)證碼的由來

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在web項(xiàng)目開發(fā)中，為了防止部分人使用自動(dòng)工具（如：自動(dòng)注冊(cè)機(jī)）等進(jìn)行批量的數(shù)據(jù)處理，在不同的功能節(jié)點(diǎn)部分，添加了驗(yàn)證碼進(jìn)行驗(yàn)證，達(dá)到對(duì)自動(dòng)軟件的屏蔽效果

最經(jīng)典的應(yīng)用如：網(wǎng)站注冊(cè)圖形驗(yàn)證碼；接下來，通過java技術(shù)，結(jié)合servlet實(shí)現(xiàn)一個(gè)網(wǎng)站注冊(cè)需要的圖形驗(yàn)證碼程序，提供大家參考。

二實(shí)現(xiàn)注冊(cè)頁面圖形驗(yàn)證碼效果

1. 創(chuàng)建web項(xiàng)目：java_servlet_verifyimg

2. 創(chuàng)建自動(dòng)生成圖形驗(yàn)證碼的控制器——VerifyImgServlet

package com.phome.util;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class VerifyImgServlet extends HttpServlet {

 /**
  * 
  */
 private static final long serialVersionUID = 1L;

 // 設(shè)置隨機(jī)字符字典。其中不包含0,o,1,I等難以辨認(rèn)的字符
 public static final char[] CHARS = { '2', '3', '4', '5', '6', '7', '8',
   '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M',
   'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a',
   'b', 'c', 'd', 'e', 'f', 'g', 'h', 'j', 'k', 'l', 'm', 'n', 'p',
   'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z' };

 public static Random random = new Random(); // 隨機(jī)數(shù)對(duì)象

 public static String getRandomString() {

  StringBuffer buffer = new StringBuffer(); // 字符串緩存
  for (int i = 0; i < 6; i++) // 六次循環(huán)獲取字符
  {
   buffer.append(CHARS[random.nextInt(CHARS.length)]); // 每次隨機(jī)取一個(gè)字符
  }
  return buffer.toString();
 }

 public static Color getRandomColor() {

  return new Color(random.nextInt(255), random.nextInt(255),
    random.nextInt(255));
 }

 public static Color getReverseColor(Color c) {

  return new Color(255 - c.getRed(), 255 - c.getGreen(),
    255 - c.getBlue());
 }

 public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {

  response.setContentType("image/jpeg"); // 設(shè)置輸出類型 不可省略

  String randomString = getRandomString(); // 調(diào)用生成隨機(jī)字符串方法獲取并接受隨機(jī)字符串
  request.getSession(true).setAttribute("randomString", randomString); // 將字符串存儲(chǔ)到Session中

  int width = 100; // 圖片寬度
  int height = 30; // 圖片高度

  Color color = getRandomColor(); // 獲取隨機(jī)顏色 用于背景色
  Color reverse = getReverseColor(color); // 反色 用于前景色

  BufferedImage bi = new BufferedImage(width, height,
    BufferedImage.TYPE_INT_RGB); // 創(chuàng)建一個(gè)彩色圖片
  Graphics2D g = bi.createGraphics(); // 獲取繪圖對(duì)象
  g.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 16)); // 設(shè)置字體
  g.setColor(color); // 設(shè)置顏色
  g.fillRect(0, 0, width, height); // 繪制背景
  g.setColor(reverse); // 設(shè)置顏色
  g.drawString(randomString, 18, 20); // 繪制隨機(jī)字符
  for (int i = 0, n = random.nextInt(100); i < n; i++) // 畫最多一百個(gè)噪音點(diǎn)
  {
   g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1); // 隨機(jī)噪音點(diǎn)
  }

  ServletOutputStream out = response.getOutputStream(); // 好像是獲取輸出流

  JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out); // 編碼器
  encoder.encode(bi); // 對(duì)圖片進(jìn)行編碼
  out.flush(); // 輸出到客戶端

 }

 public void doPost(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {

  this.doGet(request, response);
 }

}

3. 創(chuàng)建注冊(cè)控制器——RegistServlet

package com.phome.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 * 注冊(cè)控制器
 * @author ZuoYi
 *
 */
public class RegistServlet extends HttpServlet{

 /**
  * 
  */
 private static final long serialVersionUID = 1L;

 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp)
   throws ServletException, IOException {
  this.doPost(req, resp);
 }

 @Override
 protected void doPost(HttpServletRequest req, HttpServletResponse resp)
   throws ServletException, IOException {
  // 從session中獲取注冊(cè)隨機(jī)驗(yàn)證碼
  HttpSession session = req.getSession();
  String randomString = (String)session.getAttribute("randomString");
  
  // 獲取用戶輸入驗(yàn)證碼
  String inputRandomString = req.getParameter("randomStr");
  // 判斷驗(yàn)證碼通過，模擬進(jìn)行注冊(cè)
  if (randomString.equals(inputRandomString)) {
   req.setAttribute("resinfo", "恭喜！注冊(cè)成功！");
  } else {
   req.setAttribute("resinfo", "驗(yàn)證碼輸入有誤，請(qǐng)檢查后重新進(jìn)行注冊(cè)！");
  }
  // 注冊(cè)成功或者失敗，都跳轉(zhuǎn)到result.jsp頁面，查看注冊(cè)結(jié)果。。。
  req.getRequestDispatcher("result.jsp").forward(req, resp);
 }
 
 
}

4. 配置servlet

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
 <display-name>simg</display-name>
 
 <!-- 配置用戶注冊(cè)servlet -->
 <servlet>
  <servlet-name>registservlet</servlet-name>
  <servlet-class>com.phome.servlet.RegistServlet</servlet-class>
 </servlet>
 <servlet-mapping>
  <servlet-name>registservlet</servlet-name>
  <url-pattern>/regist.action</url-pattern>
 </servlet-mapping>
 
 <!-- 配置圖形驗(yàn)證碼servlet -->
 <servlet>
  <servlet-name>verifyimg</servlet-name>
  <servlet-class>com.phome.servlet.VerifyImgServlet</servlet-class>
 </servlet>
 <servlet-mapping>
  <servlet-name>verifyimg</servlet-name>
  <url-pattern>/verifyimg.action</url-pattern>
 </servlet-mapping>
 
 <welcome-file-list>
 <welcome-file>index.html</welcome-file>
 <welcome-file>index.htm</welcome-file>
 <welcome-file>index.jsp</welcome-file>
 <welcome-file>default.html</welcome-file>
 <welcome-file>default.htm</welcome-file>
 <welcome-file>default.jsp</welcome-file>
 </welcome-file-list>
</web-app>

5. 創(chuàng)建注冊(cè)視圖測(cè)試頁面——regist.jsp

<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
 <head>
 <base href="<%=basePath%>" rel="external nofollow" rel="external nofollow" >
 
 <title>My JSP 'index.jsp' starting page</title>
 <meta http-equiv="pragma" content="no-cache">
 <meta http-equiv="cache-control" content="no-cache">
 <meta http-equiv="expires" content="0"> 
 <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
 <meta http-equiv="description" content="This is my page">
 <!--
 <link rel="stylesheet" type="text/css" href="styles.css" rel="external nofollow" rel="external nofollow" >
 -->
 </head>
 <body>
 <form action="${pageContext.request.contextPath}/regist.action" method="post">
  用戶名：<input type="text" name="username"/>
 <br />
  密碼：<input type="text" name="password"/>
 <br />
  請(qǐng)輸入驗(yàn)證碼進(jìn)行注冊(cè)：
 <img src="${pageContext.request.contextPath }/verifyimg.action"/>
 <input type="text" name="randomStr"/>
 <br />
 <input type="submit" value="regist"/>  
 </form>
 </body>
</html>

5.1 創(chuàng)建注冊(cè)結(jié)果頁面——result.jsp

<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
 <head>
 <base href="<%=basePath%>" rel="external nofollow" rel="external nofollow" >
 
 <title>My JSP 'index.jsp' starting page</title>
 <meta http-equiv="pragma" content="no-cache">
 <meta http-equiv="cache-control" content="no-cache">
 <meta http-equiv="expires" content="0"> 
 <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
 <meta http-equiv="description" content="This is my page">
 <!--
 <link rel="stylesheet" type="text/css" href="styles.css" rel="external nofollow" rel="external nofollow" >
 -->
 </head>
 <body>
 ${requestScope.resinfo }
 </body>
</html>

6.測(cè)試

（1）a.打開瀏覽器，輸入測(cè)試地址：http://localhost:8080/java_servlet_verifyimg；出現(xiàn)如下圖所示頁面