JavaWeb实现登录验证码

在登录界面中使用图片验证码, 对于现在的web应用到处可见.

话不多说, 开始写代码了!
首先, 新建一个JSP, 表示登录界面:
login3.jsp文件:

<%--User: menglanyingfeiDate: 2018/1/12Time: 16:16
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head><title>登录界面</title>
</head>
<body>
<%// 获取浏览器发送过来的cookie, 获取用户信息Cookie[] cookies = request.getCookies();String username = "";if (cookies != null) {for (Cookie cookie : cookies) {if ("username".equals(cookie.getName())) {username = cookie.getValue();}}}
%>
<font color="red">${requestScope.message}</font>
<form action="/day_1_12/LoginServlet3" method="post">用户名:<input type="text" name="username" value="<%= username%>"><font color="red">${requestScope.error}</font><br>密码:<input type="password" name="password"><br>验证码:<input type="text" name="image"><img src="/day_1_12/VerifyCodeServlet"><input type="button" value="看不清? 换一张." id="btn"><font color="red">${requestScope.imageMess}</font><br><input type="submit" value="登录">
</form>
<script type="text/javascript">document.getElementById("btn").onclick = function () {// 获取img元素// 为了让浏览器发送请求到servlet, 所以一定要改变srcdocument.getElementsByTagName("img")[0].src ="/day_1_12/VerifyCodeServlet?time=" + new Date().getTime();};
</script></body>
</html>

界面就是这样, 当然, 你肯定现在出来不了这个效果! 没事, 接着往下看吧!

然后, 新建一个Servlet:
VerifyCodeServlet.java文件, 因为这里配置了@WebServlet注解, 所以无需在web.xml中配置!

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.image.BufferedImage;
import java.io.IOException;/*** 用来生成图片验证码* Created by menglanyingfei on 2018/1/12.*/
@WebServlet(name = "VerifyCodeServlet", value = "/VerifyCodeServlet")
public class VerifyCodeServlet extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//创建对象VerifyCode vc = new VerifyCode();//获取图片对象BufferedImage bi = vc.getImage();//获得图片的文本内容String text = vc.getText();// 将系统生成的文本内容保存到session中request.getSession().setAttribute("text", text);//向浏览器输出图片vc.output(bi, response.getOutputStream());}
}

在同一包下, 新建一个Java文件VerifyCode.java(具体的代码意思, 可以看注释, 已经写得非常清楚了!):

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;import javax.imageio.ImageIO;public class VerifyCode {private int w = 70;private int h = 35;private Random r = new Random();// {"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"};// 可选字符private String codes  = "0123456789abcdefghjkmnopqrstuvwxyzABCDEFGHJKMNPQRSTUVWXYZ";// 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 ~ 28return 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BufferedImageprivate BufferedImage createImage () {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;}// 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.textdrawLine(image); //添加干扰线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);}
}

处理登录逻辑的Servlet(LoginServlet3.java):

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;/*** Created by menglanyingfei on 2018/1/12.*/
@WebServlet(name = "LoginServlet3", value = "/LoginServlet3")
public class LoginServlet3 extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// 编码request.setCharacterEncoding("utf-8");// 获取请求参数/*拿到页面传过来的手动输入的验证码, 该验证码要和生成图片上的文本验证码比较, 如果相同, 验证码输入成功!*/String imageText = request.getParameter("image");// 图片的验证码String text = (String) request.getSession().getAttribute("text");if (!text.equalsIgnoreCase(imageText)) {request.setAttribute("imageMess", "验证码输入错误!");request.getRequestDispatcher("/jsp/login3.jsp").forward(request, response);}// 获取用户名和密码String username = request.getParameter("username");String password = request.getParameter("password");if ("haha".equals(username) && "123".equals(password)) {// 将用户信息保存到session中request.getSession().setAttribute("username", username);// 使用cookie实现回写用户名Cookie cookie = new Cookie("username", username);cookie.setMaxAge(60 * 60);// 通过响应头发送cookieresponse.addCookie(cookie);// 重定向登录成功界面response.sendRedirect(request.getContextPath() + "/jsp/success2.jsp");} else {request.setAttribute("error", "用户名或密码错误!");request.getRequestDispatcher("/jsp/login3.jsp").forward(request, response);}}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {}
}

登录成功后的界面:(success2.jsp)

<%--User: menglanyingfeiDate: 2018/1/12Time: 16:44
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head><title>成功登录</title>
</head>
<body>
<%// 获取用户信息String username = (String) session.getAttribute("username");if (username == null) {// 保存错误信息到request中, 然后转发到login3.jsp中, 提醒登录request.setAttribute("message", "请登录!");// 转发到登录页面request.getRequestDispatcher("/jsp/login3.jsp").forward(request, response);}
%>
<h2>欢迎登录:${sessionScope.username}!!!</h2>
</body>
</html>

最后, 演示登录:
因为, 用户名haha和密码123已经写死在代码里了!

完整代码地址

https://github.com/menglanyingfei/Java/tree/master/JavaWebTrain/day_1_12

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JavaWeb实现登录验证码

完整代码地址

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