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建设工程施工合同范本哪个网站,网站建设 gei l f,二一九wordpress,WordPress建站经验一、实现一个简单登录验证程序实现一个简单的用户登录验证程序，如果用户名是 abc ，密码是 123，则显示欢迎用户的信息，否则显示“用户名或密码不正确”。【分析】该案例采用 JSP 页面只完成提交信息和验证结果的显示&#xff…

一、实现一个简单登录验证程序

实现一个简单的用户登录验证程序，如果用户名是 abc ，密码是 123，则显示欢迎用户的信息，否则显示“用户名或密码不正确”。

【分析】该案例采用 JSP 页面只完成提交信息和验证结果的显示，而验证过程由 Servlet 完成，这些组件通过 request （或 HttpServletRequest）对象实现数据共享。由提交页面将数据传递给 Servlet，而 Servlet 获取数据并实现验证，根据验证结果，转向显示验证结果的页面。

【设计】根据分析，该系统需要设计3个组件以及修改 web.xml 文件。

（1）登录表单页面： login.jsp。

（2）处理登录请求并实现验证的 Servlet：LoginCheckServlet.java。

（3）显示提示的页面： Info.jsp。

（4）修改 web.xml，配置 Servlet的信息。

假设，表单传递的参数为 username 和 userpwd。

1.登录表单页面login.jsp：

<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>登录页面</title>
</head>
<body>
<form action="CheckServlet" method="post"><table><tr align="center"><td>请输入用户名：<input type="text" name="username" size="20"></td></tr><tr align="center"><td>请输入密码：&nbsp;&nbsp;<input type="password" name="userpwd"size="20"></td></tr align="center"><td><input type="submit" value="登录" /> <input type="reset" /></td></tr></table>
</form>
</body>
</html>

2.处理登录的 Servlet：LoginCheckServlet.java

package servlet;import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;public class LoginCheckServlet extends HttpServlet {private static final long serialVersionUID = 1L;protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {String userName = request.getParameter("username");String userPwd = request.getParameter("userpwd");String info = "";if(("abc".equals(userName))&&"123".equals(userPwd)){info = "欢迎你"+userName+"！";}else{info = "用户名或密码不正确！";}request.setAttribute("outputMessage", info);request.getRequestDispatcher("/info.jsp").forward(request,response);}
}

3.显示提示的页面 info.jsp：

<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<%=request.getAttribute("outputMessage") %>
</body>
</html>

4.修改配置文件，在 web.xml 中，修改LoginCheckServlet 的配置信息：

在这里插入图片描述
注意:与前面的表单action路径一致

5.运行效果图

输入正确的用户名和密码

输入错误的用户名和密码

二、实现一个带验证码登录验证程序

1.前端的登陆页面如下：login.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8"%>
<html>
<head><title>Title</title>
</head>
<body><form action="login" method="post">姓名：<input name="name" type="text"><br><br>密码：<input name="password" type="password"><br><br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<input name="vericode" placeholder="验证码" value="" style="width: 60px">&nbsp;&nbsp;<img id="vericodeImg" src="imageCode">&nbsp;&nbsp;<a id="kanbuq" href="javascript:changeImg();">看不清，换一张</a><br><br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<input type="submit" value="提交"></form><script src="https://code.jquery.com/jquery-3.4.1.min.js"></script><script type="text/javascript">function changeImg() {//需要让每次请求的url都发生变化。否则服务器会认为访问的时一张图片，就不会刷新请求了//每次url一样，服务器会认为访问的url是同一张图片，没变化啊$("#vericodeImg").attr("src","imageCode?"+Math.random())}</script>
</body>
</html>

2.后端的LoginServlet登陆实现逻辑如下：LoginServlet.java

映射的url-patten: /login

package servlet;import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;public class LoginServlet extends HttpServlet {private static final long serialVersionUID = 1L;protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {}protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {response.setContentType("text/html;charset=utf8");String name=request.getParameter("name");String password=request.getParameter("password");String vericode=request.getParameter("vericode");String generatedCode= (String) request.getSession().getAttribute("verityCode");if (name.equals("bob")&&password.equals("123")&&vericode.toLowerCase().equals(generatedCode.toLowerCase())){response.getWriter().write("登录成功");}else {response.getWriter().write("登录失败");}}}

3.下面是两个工具代码：生成验证码字符串CreateVerificationCode.java

package bean;import java.util.Arrays;public class CreateVerificationCode {/*** 验证码难度级别*/public enum SecurityCodeLevel {Simple,Medium,Hard}public static String getSecurityCode() {return (String) getSecurityCode(4, SecurityCodeLevel.Medium, false);}public static String getSecurityCode(int length, SecurityCodeLevel level, boolean isCanRepeat) {int len = length;//除去容易混淆的0和o，1和lchar[] codes = {'1', '2', '3', '4', '5', '6', '7', '8', '9','a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i','j', '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'};if(level==SecurityCodeLevel.Simple){codes= Arrays.copyOfRange(codes,0,9);}else if (level==SecurityCodeLevel.Medium){codes= Arrays.copyOfRange(codes,0,33);}int n=codes.length;//抛出运行时异常if (len>n&&isCanRepeat==false){throw new RuntimeException(String.format("调用securitycode.getSecurityCode(%1$s,len,level,isCanRepeat,n)"));}char[] result=new char[len];//判断能否出现重复的字符if (isCanRepeat){for(int i=0;i<result.length;i++){//索引0 and n-1int r=(int)(Math.random()*n);//将result中的第i个元素设为codes[r]存放的数值result[i]=codes[r];}}else {for (int i=0;i<result.length;i++){int r=(int)(Math.random()*n);//将result中的第i个元素设为codes[r]存放的数值result[i]=codes[r];codes[r]=codes[n-1];n--;}}return String.valueOf(result);}
}

4.生成验证码图片（它是基于生成验证码字符串类的）CreateVerificationCodeImage.java

package bean;import java.awt.*;
import java.awt.image.BufferedImage;
import java.util.Random;/*** 可生成数字，大写，小写字母及三者混合类型的验证码，支持自定义干扰线，图文颜色*/
public class CreateVerificationCodeImage {private String securityCode;public CreateVerificationCodeImage(String securityCode){this.securityCode=securityCode;}//高度private static final int CAPTCHA_HEIGHT = 35;//宽度private static final int CAPTCHA_WIDTH  = 100;//数字的长度//private static final int NUMBER_CNT     = 6;private Random r = new Random();//  字体private String[] fontNames = { "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",  "黑体", "微软雅黑"};/*** 机能概要:生成随机的颜色* @return*/private Color randomColor() {int red = r.nextInt(150);int green = r.nextInt(150);int blue = r.nextInt(150);return new Color(red, green, blue);}/*** 机能概要:生成随机的字体* @return*/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// int size = r.nextInt(5) + 15; // 生成随机字号, 20 ~ 24return new Font(fontName, style, size);}// 画干扰线private  void drawLine(BufferedImage image) {int num = 5;// 一共画5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(CAPTCHA_WIDTH);int y1 = r.nextInt(CAPTCHA_HEIGHT);int x2 = r.nextInt(CAPTCHA_WIDTH);int y2 = r.nextInt(CAPTCHA_HEIGHT);g2.setStroke(new BasicStroke(1.5F));g2.setColor(randomColor()); // 随机生成干扰线颜色g2.drawLine(x1, y1, x2, y2);// 画线}}// 创建BufferedImage，生成图片public BufferedImage createImage() {BufferedImage image = new BufferedImage(CAPTCHA_WIDTH, CAPTCHA_HEIGHT, BufferedImage.TYPE_INT_RGB);Graphics2D g2 = (Graphics2D) image.getGraphics();// 背景色,白色g2.setColor(new Color(255, 255, 255));g2.fillRect(0, 0, CAPTCHA_WIDTH, CAPTCHA_HEIGHT);// 向图片中画4个字符  String securityCodefor (int i = 0; i < securityCode.length(); i++) {// 循环四次，每次生成一个字符String s = securityCode.charAt(i) + "";// 随机生成一个字母// float x = i * 1.0F * CAPTCHA_WIDTH / NUMBER_CNT; // 设置当前字符的x轴坐标float x = i * 1.0F * CAPTCHA_WIDTH / 4+7F; // 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, CAPTCHA_HEIGHT-7); // 画图,依次将字符写入到图片的相应位置-------------------}drawLine(image); // 添加干扰线return image;}
}

5）调用工具类的生成验证码图片的方法，在通过response对象，将图片流返回给前端，有img标签的src属性负责解析：ImageCodeServelt.java
映射的url-patten: /imageCode

package servlet;import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import jakarta.servlet.http.HttpSession;import java.io.IOException;import javax.imageio.ImageIO;import bean.CreateVerificationCode;
import bean.CreateVerificationCodeImage;public class ImageCodeServelt extends HttpServlet {private static final long serialVersionUID = 1L;protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {String vericode= CreateVerificationCode.getSecurityCode();HttpSession session=request.getSession();session.setAttribute("verityCode",vericode);//设置返回的内容response.setContentType("img/jpeg");//浏览器不缓存响应内容--验证码图片，点一次就要刷新一次，所以不能有缓存出现response.setHeader("Pragma","No-cache");response.setHeader("Cache-Control","no-cache");//设置验证码失效时间response.setDateHeader("Expires",0);//以字节流发过去，交给img的src属性去解析即可ImageIO.write(new CreateVerificationCodeImage(vericode).createImage(),"JPEG",response.getOutputStream());}protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}}