java web开发之servlet图形验证码功能的实现

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

b.输入注册账号、密码和验证码后点击regist提交

c.测试结果，跳转会注册页面，提示注册成功

（2）打开注册页面

输入错误注册码

测试结果页面

over!

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持我们。