工具类：
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 }}VerifyCodeServlet：
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()); }}LoginServlet:
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 } } }login.jsp:
<%@ 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cookieif(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>loginsuccess：
<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;}%>欢迎欢迎，热烈欢迎，欢迎<%=username %>领导指导工作！
</body></html>
配置文件：
<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>
建议：生成验证码的Servlet最好设置成不缓存，这样就不用再页面请求验证码图片的时候加上时间戳了，加上时间戳就是欺骗浏览器防止浏览器读取缓存里的验证码图片，而点击换一张后没反应。 这样的不是很好的一点就是，每次点击换一张，浏览器都会把新获取的图片缓存到本地，而在Servlet里设置不缓存，就不会缓存到本地了。
总结
以上所述是小编给大家介绍的JAVA验证码工具实例代码，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对武林网网站的支持！