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Java web（五）：会话技术

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文章目录

  • 一、会话跟踪技术
  • 二、Cookie
  • 三、Session
  • 四、Cookie和Session的区别
  • 五、项目实战

一、会话跟踪技术

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二、Cookie

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在JSP页面如何获取Cookie？
方式：${cookie.key.value} //key指存在cookie的键的名称

三、Session

Session是基于Cookie实现的，不同浏览器请求的不同的Session（通过Cookie的id区分）
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注意：1. 服务器正常关闭，session不会销毁；2. 当浏览器关闭后再次访问服务器，由于前后两次不是同一个会话，所以第二次打开浏览访问的session与前一个不同。

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上述第一种销毁方式要写进webapp/WEB-INF/web.xml中

四、Cookie和Session的区别

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五、项目实战

实现功能

  1. 用户登录、记住用户名密码
  2. 用户注册、验证码

这里展示主要代码
login.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<html lang="en"><head><meta charset="UTF-8"><title>login</title><link href="css/login.css" rel="stylesheet">
</head><body>
<div id="loginDiv" style="height: 350px"><form action="/brand-demo/loginServlet" id="form"><h1 id="loginMsg">LOGIN IN</h1><div id="errorMsg">${login_msg} ${register_msg}</div><p>Username:<input id="username" name="username" value="${cookie.username.value}" type="text"></p><p>Password:<input id="password" name="password" value="${cookie.password.value}" type="password"></p><p>Remember:<input id="remember" name="remember" type="checkbox"></p><div id="subDiv"><input type="submit" class="button" value="login up"><input type="reset" class="button" value="reset">&nbsp;&nbsp;&nbsp;<a href="/brand-demo/register.jsp">没有账号？</a></div></form>
</div></body>
</html>

register.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false"%>
<html lang="en">
<head><meta charset="UTF-8"><title>欢迎注册</title><link href="css/register.css" rel="stylesheet">
</head>
<body><div class="form-div"><div class="reg-content"><h1>欢迎注册</h1><span>已有帐号？</span> <a href="login.html">登录</a></div><form id="reg-form" action="/brand-demo/registerServlet" method="post"><table><tr><td>用户名</td><td class="inputs"><input name="username" type="text" id="username"><br><span id="username_err" class="err_msg">${register_msg}</span></td></tr><tr><td>密码</td><td class="inputs"><input name="password" type="password" id="password"><br><span id="password_err" class="err_msg" style="display: none">密码格式有误</span></td></tr><tr><td>验证码</td><td class="inputs"><input name="checkCode" type="text" id="checkCode"><img id="checkCodeImg" src="/brand-demo/checkCodeServlet"><a href="#" id="changeImg">看不清？</a></td></tr></table><div class="buttons"><input value="注 册" type="submit" id="reg_btn"></div><br class="clear"></form></div>
<script>document.getElementById("changeImg").onclick = function (){// 加上时间的目的是：每生成一个验证码会有一个缓存，要保证验证码的不同加上了时间document.getElementById("checkCodeImg").src = "/brand-demo/checkCodeServlet?" + new Date().getMilliseconds()}
</script>
</body>
</html>

注意：每生成一个验证码要加上名字辨识，因为生成一个二维码会有缓存，不加辨识无法生成一个新的code

LoginServlet.java

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {UserService userService = new UserService();@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {String username = req.getParameter("username");String password = req.getParameter("password");String remember = req.getParameter("remember");User user = userService.loginUser(username, password);if(user!=null){//将username与password存入cookieif("on".equals(remember)){Cookie c_username1 = new Cookie("username", username);Cookie c_password1 = new Cookie("password", password);c_username1.setMaxAge(60*60*24*7);c_password1.setMaxAge(60*60*24*7);resp.addCookie(c_username1);resp.addCookie(c_password1);}//登录成功后将user存储到sessionHttpSession session = req.getSession();session.setAttribute("user",user);String contextPath = req.getContextPath();resp.sendRedirect(contextPath+"/selectAllServlet");} else{req.setAttribute("login_msg","登录失败");req.getRequestDispatcher("/login.jsp").forward(req,resp);}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {this.doGet(req,resp);}
}

RegisterServlet.java

@WebServlet("/registerServlet")
public class RegisterServlet extends HttpServlet {UserService userService = new UserService();@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {String username = req.getParameter("username");String password = req.getParameter("password");String checkCode = req.getParameter("checkCode");//从session中获取验证码HttpSession session = req.getSession();String checkCodeGen = (String)session.getAttribute("checkCodeGen");if(!checkCodeGen.equals(checkCode)){req.setAttribute("register_msg","验证码错误");req.getRequestDispatcher("/register.jsp").forward(req,resp);return;}User user1 = new User();user1.setUsername(username);user1.setPassword(password);boolean flag = userService.registerUser(user1);if(flag){req.setAttribute("register_msg","注册成功");req.getRequestDispatcher("/login.jsp").forward(req,resp);} else {System.out.println("failure");req.setAttribute("register_msg","用户名已存在");req.getRequestDispatcher("/register.jsp").forward(req,resp);}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {this.doGet(req,resp);}
}

CheckCodeServlet.java 生成验证码

@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {ServletOutputStream outputStream = resp.getOutputStream();String checkcode = CheckCodeUtil.outputVerifyImage(100, 50, outputStream, 4);// 将验证码存入session中HttpSession session = req.getSession();session.setAttribute("checkCodeGen",checkcode);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {this.doGet(req,resp);}
}

CheckCodeUtils.java验证码图片生成类

package com.bhy.utils;import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.*;
import java.util.Arrays;
import java.util.Random;/*** 生成验证码工具类*/
public class CheckCodeUtil {public static final String VERIFY_CODES = "123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";private static Random random = new Random();public static void main(String[] args) throws IOException {OutputStream fos = new FileOutputStream("d://a.jpg");String checkCode = CheckCodeUtil.outputVerifyImage(100, 50, fos, 4);System.out.println(checkCode);}/*** 输出随机验证码图片流,并返回验证码值（一般传入输出流，响应response页面端，Web项目用的较多）** @param width 图片宽度* @param height 图片高度* @param os  输出流* @param verifySize 数据长度* @return 验证码数据* @throws IOException*/public static String outputVerifyImage(int width, int height, OutputStream os, int verifySize) throws IOException {String verifyCode = generateVerifyCode(verifySize);outputImage(width, height, os, verifyCode);return verifyCode;}/*** 使用系统默认字符源生成验证码** @param verifySize 验证码长度* @return*/public static String generateVerifyCode(int verifySize) {return generateVerifyCode(verifySize, VERIFY_CODES);}/*** 使用指定源生成验证码** @param verifySize 验证码长度* @param sources    验证码字符源* @return*/public static String generateVerifyCode(int verifySize, String sources) {// 未设定展示源的字码，赋默认值大写字母+数字if (sources == null || sources.length() == 0) {sources = VERIFY_CODES;}int codesLen = sources.length();Random rand = new Random(System.currentTimeMillis());StringBuilder verifyCode = new StringBuilder(verifySize);for (int i = 0; i < verifySize; i++) {verifyCode.append(sources.charAt(rand.nextInt(codesLen - 1)));}return verifyCode.toString();}/*** 生成随机验证码文件,并返回验证码值 (生成图片形式，用的较少)** @param w* @param h* @param outputFile* @param verifySize* @return* @throws IOException*/public static String outputVerifyImage(int w, int h, File outputFile, int verifySize) throws IOException {String verifyCode = generateVerifyCode(verifySize);outputImage(w, h, outputFile, verifyCode);return verifyCode;}/*** 生成指定验证码图像文件** @param w* @param h* @param outputFile* @param code* @throws IOException*/public static void outputImage(int w, int h, File outputFile, String code) throws IOException {if (outputFile == null) {return;}File dir = outputFile.getParentFile();//文件不存在if (!dir.exists()) {//创建dir.mkdirs();}try {outputFile.createNewFile();FileOutputStream fos = new FileOutputStream(outputFile);outputImage(w, h, fos, code);fos.close();} catch (IOException e) {throw e;}}/*** 输出指定验证码图片流** @param w* @param h* @param os* @param code* @throws IOException*/public static void outputImage(int w, int h, OutputStream os, String code) throws IOException {int verifySize = code.length();BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);Random rand = new Random();Graphics2D g2 = image.createGraphics();g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);// 创建颜色集合，使用java.awt包下的类Color[] colors = new Color[5];Color[] colorSpaces = new Color[]{Color.WHITE, Color.CYAN,Color.GRAY, Color.LIGHT_GRAY, Color.MAGENTA, Color.ORANGE,Color.PINK, Color.YELLOW};float[] fractions = new float[colors.length];for (int i = 0; i < colors.length; i++) {colors[i] = colorSpaces[rand.nextInt(colorSpaces.length)];fractions[i] = rand.nextFloat();}Arrays.sort(fractions);// 设置边框色g2.setColor(Color.GRAY);g2.fillRect(0, 0, w, h);Color c = getRandColor(200, 250);// 设置背景色g2.setColor(c);g2.fillRect(0, 2, w, h - 4);// 绘制干扰线Random random = new Random();// 设置线条的颜色g2.setColor(getRandColor(160, 200));for (int i = 0; i < 20; i++) {int x = random.nextInt(w - 1);int y = random.nextInt(h - 1);int xl = random.nextInt(6) + 1;int yl = random.nextInt(12) + 1;g2.drawLine(x, y, x + xl + 40, y + yl + 20);}// 添加噪点// 噪声率float yawpRate = 0.05f;int area = (int) (yawpRate * w * h);for (int i = 0; i < area; i++) {int x = random.nextInt(w);int y = random.nextInt(h);// 获取随机颜色int rgb = getRandomIntColor();image.setRGB(x, y, rgb);}// 添加图片扭曲shear(g2, w, h, c);g2.setColor(getRandColor(100, 160));int fontSize = h - 4;Font font = new Font("Algerian", Font.ITALIC, fontSize);g2.setFont(font);char[] chars = code.toCharArray();for (int i = 0; i < verifySize; i++) {AffineTransform affine = new AffineTransform();affine.setToRotation(Math.PI / 4 * rand.nextDouble() * (rand.nextBoolean() ? 1 : -1), (w / verifySize) * i + fontSize / 2, h / 2);g2.setTransform(affine);g2.drawChars(chars, i, 1, ((w - 10) / verifySize) * i + 5, h / 2 + fontSize / 2 - 10);}g2.dispose();ImageIO.write(image, "jpg", os);}/*** 随机颜色** @param fc* @param bc* @return*/private static Color getRandColor(int fc, int bc) {if (fc > 255) {fc = 255;}if (bc > 255) {bc = 255;}int r = fc + random.nextInt(bc - fc);int g = fc + random.nextInt(bc - fc);int b = fc + random.nextInt(bc - fc);return new Color(r, g, b);}private static int getRandomIntColor() {int[] rgb = getRandomRgb();int color = 0;for (int c : rgb) {color = color << 8;color = color | c;}return color;}private static int[] getRandomRgb() {int[] rgb = new int[3];for (int i = 0; i < 3; i++) {rgb[i] = random.nextInt(255);}return rgb;}private static void shear(Graphics g, int w1, int h1, Color color) {shearX(g, w1, h1, color);shearY(g, w1, h1, color);}private static void shearX(Graphics g, int w1, int h1, Color color) {int period = random.nextInt(2);boolean borderGap = true;int frames = 1;int phase = random.nextInt(2);for (int i = 0; i < h1; i++) {double d = (double) (period >> 1)* Math.sin((double) i / (double) period+ (6.2831853071795862D * (double) phase)/ (double) frames);g.copyArea(0, i, w1, 1, (int) d, 0);if (borderGap) {g.setColor(color);g.drawLine((int) d, i, 0, i);g.drawLine((int) d + w1, i, w1, i);}}}private static void shearY(Graphics g, int w1, int h1, Color color) {int period = random.nextInt(40) + 10; // 50;boolean borderGap = true;int frames = 20;int phase = 7;for (int i = 0; i < w1; i++) {double d = (double) (period >> 1)* Math.sin((double) i / (double) period+ (6.2831853071795862D * (double) phase)/ (double) frames);g.copyArea(i, 0, 1, h1, 0, (int) d);if (borderGap) {g.setColor(color);g.drawLine(i, (int) d, i, 0);g.drawLine(i, (int) d + h1, i, h1);}}}
}
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