java web开发之servlet图形验证码功能的实现

发布时间：2020-10-13 20:22:41 作者：大牧莫邪
来源：脚本之家阅读：178

一验证码的由来

在web项目开发中，为了防止部分人使用自动工具（如：自动注册机）等进行批量的数据处理，在不同的功能节点部分，添加了验证码进行验证，达到对自动软件的屏蔽效果

最经典的应用如：网站注册图形验证码；接下来，通过java技术，结合servlet实现一个网站注册需要的图形验证码程序，提供大家参考。

二实现注册页面图形验证码效果

1. 创建web项目：java_servlet_verifyimg

2. 创建自动生成图形验证码的控制器——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;

 // 设置随机字符字典。其中不包含0,o,1,I等难以辨认的字符
 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(); // 随机数对象

 public static String getRandomString() {

  StringBuffer buffer = new StringBuffer(); // 字符串缓存
  for (int i = 0; i < 6; i++) // 六次循环获取字符
  {
   buffer.append(CHARS[random.nextInt(CHARS.length)]); // 每次随机取一个字符
  }
  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"); // 设置输出类型 不可省略

  String randomString = getRandomString(); // 调用生成随机字符串方法获取并接受随机字符串
  request.getSession(true).setAttribute("randomString", randomString); // 将字符串存储到Session中

  int width = 100; // 图片宽度
  int height = 30; // 图片高度

  Color color = getRandomColor(); // 获取随机颜色 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); // 创建一个彩色图片
  Graphics2D g = bi.createGraphics(); // 获取绘图对象
  g.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 16)); // 设置字体
  g.setColor(color); // 设置颜色
  g.fillRect(0, 0, width, height); // 绘制背景
  g.setColor(reverse); // 设置颜色
  g.drawString(randomString, 18, 20); // 绘制随机字符
  for (int i = 0, n = random.nextInt(100); i < n; i++) // 画最多一百个噪音点
  {
   g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1); // 随机噪音点
  }

  ServletOutputStream out = response.getOutputStream(); // 好像是获取输出流

  JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out); // 编码器
  encoder.encode(bi); // 对图片进行编码
  out.flush(); // 输出到客户端

 }

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

  this.doGet(request, response);
 }

}

3. 创建注册控制器——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;

/**
 * 注册控制器
 * @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 {
  // 从session中获取注册随机验证码
  HttpSession session = req.getSession();
  String randomString = (String)session.getAttribute("randomString");
  
  // 获取用户输入验证码
  String inputRandomString = req.getParameter("randomStr");
  // 判断验证码通过，模拟进行注册
  if (randomString.equals(inputRandomString)) {
   req.setAttribute("resinfo", "恭喜！注册成功！");
  } else {
   req.setAttribute("resinfo", "验证码输入有误，请检查后重新进行注册！");
  }
  // 注册成功或者失败，都跳转到result.jsp页面，查看注册结果。。。
  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>
 
 <!-- 配置用户注册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>
 
 <!-- 配置图形验证码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. 创建注册视图测试页面——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="${pageContext.request.contextPath}/regist.action" method="post">
  用户名：<input type="text" name="username"/>
 <br />
  密码：<input type="text" name="password"/>
 <br />
  请输入验证码进行注册：
 <img src="${pageContext.request.contextPath }/verifyimg.action"/>
 <input type="text" name="randomStr"/>
 <br />
 <input type="submit" value="regist"/>  
 </form>
 </body>
</html>

5.1 创建注册结果页面——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.测试

（1）a.打开浏览器，输入测试地址：http://localhost:8080/java_servlet_verifyimg；出现如下图所示页面

java web开发之servlet图形验证码功能的实现