JAVA验证码工具实例代码

package com.lhy.web.servlet;
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;
import javax.imageio.ImageIO;
public class VerifyCode {
  private int w = 70;//图片长
  private int h = 35;//图片宽
   private Random r = new Random();//Random类 生成随机数
   // 列举验证图片中验证码的字体类型
   //{"宋体", "华文楷体", "黑体", "华文新魏", "华文隶书", "微软雅黑", "楷体_GB2312"}
  private String[] fontNames = {"宋体", "华文楷体", "黑体", "微软雅黑", "楷体_GB2312"};
  // 验证码可选字符
  private String codes="23456789abcdefghjkmnopqrstuvwxyzABCDEFGHJKMNPQRSTUVWXYZ";
  // 背景色
  private Color bgColor = new Color(255, 255, 255);
  // 验证码上的文本
  private String text ;
  // 生成随机的颜色
  private Color randomColor () {
      int red = r.nextInt(150);
      int green = r.nextInt(150);
      int blue = r.nextInt(150);
      return new Color(red, green, blue);
  }
  // 生成随机的字体
  private Font randomFont () {
        int index = r.nextInt(fontNames.length);
        String fontName = fontNames[index];//生成随机的字体名称
        int style = r.nextInt(4);//生成随机的样式, 0(无样式), 1(粗体), 2(斜体), 3(粗体+斜体)
        int size = r.nextInt(5) + 24; //生成随机字号, 24 ~ 28
        return new Font(fontName, style, size);
  }
  // 画干扰线
  private void drawLine (BufferedImage image) {
      int num = 3;//一共画3条
      Graphics2D g2 = (Graphics2D)image.getGraphics();
      for(int i = 0; i < num; i++) {//生成两个点的坐标，即4个值
        int x1 = r.nextInt(w);
        int y1 = r.nextInt(h);
        int x2 = r.nextInt(w);
        int y2 = r.nextInt(h); 
        g2.setStroke(new BasicStroke(1.5F)); 
        g2.setColor(Color.BLUE); //干扰线是蓝色
        g2.drawLine(x1, y1, x2, y2);//画线
      }
  }
  // 随机生成一个字符
  private char randomChar () {
      int index = r.nextInt(codes.length());
      return codes.charAt(index);
  }
  // 创建BufferedImage
  private BufferedImage createImage () {
      //宽，高，图片的类型
      BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB); 
      Graphics2D g2 = (Graphics2D)image.getGraphics(); 
      g2.setColor(this.bgColor);
      g2.fillRect(0, 0, w, h);
       return image;
  }
  // 返回验证码图片上的文本
  public String getText () {
      return text;
  }
  // 保存图片到指定的输出流
  public static void output (BufferedImage image, OutputStream out) 
          throws IOException {
      ImageIO.write(image, "JPEG", out);
  }
  // 调用这个方法得到验证码
    public BufferedImage getImage () {
        BufferedImage image = createImage();//创建图片缓冲区 
        Graphics2D g2 = (Graphics2D)image.getGraphics();//得到绘制环境
        StringBuilder sb = new StringBuilder();//用来装载生成的验证码文本
        // 向图片中画4个字符
        for(int i = 0; i < 4; i++) {//循环四次，每次生成一个字符
          String s = randomChar() + "";//随机生成一个字母 
          sb.append(s); //把字母添加到sb中
          float x = i * 1.0F * w / 4; //设置当前字符的x轴坐标
          g2.setFont(randomFont()); //设置随机字体
          g2.setColor(randomColor()); //设置随机颜色
          g2.drawString(s, x, h-5); //画图
        }
        this.text = sb.toString(); //把生成的字符串赋给了this.text
        drawLine(image); //添加干扰线
        return image;    
    }
    public static void main(String[] args) throws FileNotFoundException, IOException {
      VerifyCode vc = new VerifyCode();//创建VerifyCode类的对象
      BufferedImage bi = vc.getImage();//调用getImge()方法获得一个BufferedImage对象
      VerifyCode.output(bi, new FileOutputStream("C:/验证码3.jpg"));//调用静态方法output()方法将图片保存在文件输出流中
      System.out.println(vc.getText());//在控制台上打印验证码的文本值
    }
}

package com.lhy.web.servlet;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class VerifyCodeServlet extends HttpServlet {
  public void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    /*
     * 1. 生成图片
     * 2. 保存图片上的文本到session域中
     * 3. 把图片响应给客户端
     */
    VerifyCode vc = new VerifyCode();
    BufferedImage image = vc.getImage();
    request.getSession().setAttribute("session_vcode", vc.getText());//保存图片上的文本到session域
    VerifyCode.output(image, response.getOutputStream());
  }
}

package com.lhy.web.servlet;
import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class LoginServlet extends HttpServlet {
  public void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    /*
     * 校验验证码
     * 1. 从session中获取正确的验证码
     * 2. 从表单中获取用户填写的验证码
     * 3. 进行比较！
     * 4. 如果相同，向下运行，否则保存错误信息到request域，转发到login.jsp
     */
    String sessionCode = (String) request.getSession().getAttribute("session_vcode");
    String paramCode = request.getParameter("verifyCode");
    if(!paramCode.equalsIgnoreCase(sessionCode)) {
      request.setAttribute("msg", "验证码错误！");
      request.getRequestDispatcher("/login.jsp").forward(request, response);
      return;
    }
    /*
     * 1. 获取表单数据
     */
    // 处理中文问题
    request.setCharacterEncoding("utf-8");
    // 获取
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    /*
     * 2. 校验用户名和密码是否正确
     */
    if("itcast".equalsIgnoreCase(username)) {//登录成功
      /*
       * 附加项：把用户名保存到cookie中，发送给客户端浏览器
       * 当再次打开login.jsp时，login.jsp中会读取request中的cookie，把它显示到用户名文本框中
       */
      Cookie cookie = new Cookie("uname", username);//创建Cookie
      cookie.setMaxAge(60*60*24);//设置cookie命长为1天
      response.addCookie(cookie);//保存cookie
      /*
       * 3. 如果成功
       *  > 保存用户信息到session中
       *  > 重定向到succ1.jsp
       */
      HttpSession session = request.getSession();//获取session
      session.setAttribute("username", username);//向session域中保存用户名
      response.sendRedirect("/Test/succ1.jsp");
    } else {//登录失败
      /*
       * 4. 如果失败
       *  > 保存错误信息到request域中
       *  > 转发到login.jsp
       */
      request.setAttribute("msg", "用户名或密码错误!");
      RequestDispatcher qr = request.getRequestDispatcher("/login.jsp");//得到转发器
      qr.forward(request, response);//转发
    }
  }
  }

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%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" >
  <title>My JSP 'login.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" >
  -->
<script type="text/javascript">
function _change() {
  /*
  1. 得到img元素
  2. 修改其src
  */
  var imgEle = document.getElementById("img");
  imgEle.src = "<%=basePath%>servlet/VerifyCodeServlet?a=" + new Date().getTime();
}
</script>
 </head>
 <body>
<%-- 本页面提供登录表单，还要显示错误信息 --%>
<h1>登录</h1>
<%
/*
读取名为uname的Cookie!
如果为空显示：""
如果不为空显示：Cookie的值
*/
String uname = "";
Cookie[] cs = request.getCookies();//获取请求中所有的cookie
if(cs != null) {// 如果存在cookie
  for(Cookie c : cs) {//循环遍历所有的cookie
    if("uname".equals(c.getName())) {//查找名为uname的cookie
      uname = c.getValue();//获取这个cookie的值，给uname这个变量
    }
  }
}
%>
<%
  String message = "";
  String msg = (String)request.getAttribute("msg");//获取request域中的名为msg的属性
  if(msg != null) {
    message = msg;
  }
%>
<font color="red"><b><%=message %> </b></font>
<form action="servlet/LoginServlet" method="post">
      <%-- 把cookie中的用户名显示到用户名文本框中 --%>
  用户名：<input type="text" name="username" value="<%=uname%>"/><br/>
  密　码：<input type="password" name="password"/><br/>
  验证码：<input type="text" name="verifyCode" size="3"/>
      <img id="img" src="<%=basePath%>servlet/VerifyCodeServlet"/>
      <a href="javascript:_change()" rel="external nofollow" >换一张</a>
      <br/>
  <input type="submit" value="登录"/>
</form>
 </body>
</html>

<body>
<h1>succ1</h1>
<%
String username = (String)session.getAttribute("username");
if(username == null) {
  /*
  1. 向request域中保存错误信息，转发到login.jsp
  */
  request.setAttribute("msg", "您还没有登录!请先登录!");
  request.getRequestDispatcher("/login.jsp").forward(request, response);
  return;
}
%>

 </body>
</html>

<servlet>
  <servlet-name>LoginServlet</servlet-name>
  <servlet-class>com.lhy.web.servlet.LoginServlet</servlet-class>
 </servlet>
  <servlet-mapping>
  <servlet-name>LoginServlet</servlet-name>
  <url-pattern>/servlet/LoginServlet</url-pattern>
 </servlet-mapping>
 <servlet>
  <servlet-name>VerifyCodeServlet</servlet-name>
  <servlet-class>com.lhy.web.servlet.VerifyCodeServlet</servlet-class>
 </servlet>
  <servlet-mapping>
  <servlet-name>VerifyCodeServlet</servlet-name>
  <url-pattern>/servlet/VerifyCodeServlet</url-pattern>
 </servlet-mapping>