javaWeb注册，登陆，注销功能的实现

一：注册页面：regist.jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<script type="text/javascript">
	function changeImg(){
		document.getElementById("myImg").src='${pageContext.request.contextPath}/servlet/CheckCodeServlet?' +
				new Date().getTime();
	}
	function validataForm(){
		var username = document.getElementById("username").value;
		if(username == ""){
			alert("用户名不能为空！");
			return false;
		}
		
		var password = document.getElementById("password").value;
		if(password == ""){
			alert("密码不能为空!");
			return false;
		}
		
		var repassword = document.getElementById("repassword").value;
		if(password != repassword){
			alert("两次密码不一致！");
			return false;
		}
		
		var email = document.getElementById("email").value;
		if(email.match("^\s*\w+(?:\.{0,1}[\w-]+)*@[a-zA-Z0-9]+(?:[-.][a-zA-Z0-9]+)*\.[a-zA-Z]+\s*$")==null){
			alert("哥们儿,邮箱地址非法");
			return false;
		}
	}
</script>
</head>
<body>
	<form action="${pageContext.request.contextPath }/servlet/RegistServlet"  onsubmit="return validataForm();"   method="post">
		<table>
			<tr>
				<td>用户名：</td>
				<td><input type="text" name="username" id="username"></td>
			</tr>
			<tr>
				<td>密码：</td>
				<td><input type="passoword" name="password" id="password"></td>
			</tr>
			<tr>
				<td>确认密码：</td>
				<td><input type="password" name="repassword" id="repassword"></td>
			</tr>
			<tr>
				<td>邮箱：</td>
				<td><input type="text" name="email" id="email"></td>
			</tr>
			<tr>
				<td>验证码：</td>
				<td>
				<input type="text" name="checkcode">
				<img src="${pageContext.request.contextPath }/servlet/CheckCodeServlet" 
				onclick="changeImg();" style="cursor: pointer;" id="myImg"></td>
			</tr>
			<tr>
				<td></td>
				<td><input type="submit" value="注册"></td>
			</tr>
		</table>
	</form>
</body>
</html>



二：.验证码servlet：CheckCodeServlet.java
完成页面显示验证码的效果：

package com.itcode.view;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class CheckCodeServlet extends HttpServlet {
	
	// ctrl + shift +X 变大写      ----------- Y
	private final int WIDTH = 120;
	private final int HEIGHT = 30;
	
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		
		response.setHeader("cache-control", "no-cache");
		response.setHeader("pragma", "no-cache");
		response.setDateHeader("expires", -1);
		
		// 1.在内存中构建出一张  图片 
		BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
		
		Graphics2D graphics = (Graphics2D) image.getGraphics();
		
		// 将 背景设置 为 白色 .
		graphics.setColor(Color.WHITE);
		graphics.fillRect(0, 0, WIDTH, HEIGHT);
		
		// 状态机 
		// 画 矩形 .  之前 由于已经设置 过 颜色 ,就相当于 维护了 一个状态机, 所以 你需要 再次调用 setCorlor , 否则 就看不到 你 画 的矩形了 .
		graphics.setColor(Color.BLUE);
		graphics.drawRect(0, 0, WIDTH-1, HEIGHT-1);
		
		// 准备好 要 使用的 汉字.
//		String base ="ABCDEFGHIJKLMNOPQRST";
		 String base = "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";
		
		Random rand = new Random();
		// 设置颜色
		graphics.setColor(Color.RED);
		// 设置 字体
		graphics.setFont(new Font("宋体",Font.BOLD,18));
		
		StringBuilder sb = new StringBuilder();
		
		int m =10;
		// 在for循环中 将 汉字画上去 
		for (int i = 0; i < 4; i++) {
			int index = rand.nextInt(base.length());
			char charAt = base.charAt(index);
//			 -30 -- 30 
			
			int jiaodu = rand.nextInt(60) -30;
			
			double theta = jiaodu*Math.PI/180;
			
			graphics.rotate(theta,  m, 15);
			graphics.drawString(charAt +"", m, 20);
			sb.append(charAt);
			graphics.rotate(-theta,  m, 15);
			m+=25;
		}
		
		// 画 4 条线 
		
		graphics.setColor(Color.GREEN);
		for (int i = 0; i < 4; i++) {
			int x1 = rand.nextInt(WIDTH);
			int x2 = rand.nextInt(WIDTH);
			int y1 = rand.nextInt(HEIGHT);
			int y2 = rand.nextInt(HEIGHT);
			// 调用 该方法, 划线  两点 确定 一条直线 .   需要 4 个点 
			graphics.drawLine(x1, y1, x2, y2);
		}
		
		request.getSession().setAttribute("checkcode_session", sb.toString());
		
		// 释放 graphics 对象, 调用 该方法之后  graphic 就不能再使用了 .
		graphics.dispose();
		
		
		// 通过该 imageIO 将 内存中构建好的 图片 与 response的流 给 关联起来.
		ImageIO.write(image, "png", response.getOutputStream());
		
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		doGet(request, response);
	}

}



三：处理注册的servlet：RegistServlet.java

package com.itcode.controller;


import java.io.IOException;
import java.lang.reflect.InvocationTargetException;


import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


import org.apache.commons.beanutils.BeanUtils;


import com.itcode.model.User;
import com.itcode.model.UserOperator;


public class RegistServlet extends HttpServlet {


public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
response.getWriter().println("成功注册！");
User user = new User();
try {
BeanUtils.populate(user, request.getParameterMap());
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InvocationTargetException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
UserOperator userOperator = new UserOperator();
int UserFeedBack = userOperator.regist(user);
switch (UserFeedBack) {
case UserOperator.USERNAME_EXIST:
request.setAttribute("message", "用户名已经在在！");
// response.sendRedirect("/regist.jsp");
request.getRequestDispatcher("/regist.jsp").forward(request, response);
break;
case UserOperator.EMAIL_EXIST:
request.setAttribute("message", "邮箱已经被注册使用！");
request.getRequestDispatcher("/regist.jsp").forward(request, response);
break;
case UserOperator.SUCCESS:
response.sendRedirect("/user/login.jsp");//注意此时的路径与上面的路径的区别！
break;
default:
break;
}
}


public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {


doGet(request, response);
}


}



四：RegistServlet的所需要的类：

User类：

package com.itcode.model;

public class User {
	private String username;
	private String password;
	private String email;
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
	public String getEmail() {
		return email;
	}
	public void setEmail(String email) {
		this.email = email;
	}
}



UserOperator类：

package com.itcode.model;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.UnsupportedEncodingException;
import java.util.List;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;

public class UserOperator {
	public static final int USERNAME_EXIST=1;
	public static final int EMAIL_EXIST=2;
	public static final int SUCCESS =3;
	/**
	 * 检验注册用户数据的合法性，并返回相应的状态码。
	 * @param user
	 * @return int userFeedBack
	 */
	public int regist(User user){
		SAXReader saxReader = new SAXReader();
		Document document =null;
		try {
			  document = saxReader.read("d://users.xml");
		} catch (DocumentException e) {
			e.printStackTrace();
		}
		//1.得到文件的根标签:users
		Element rootElement = document.getRootElement();
		//2.由根标签得到所有的用户标签：user
		List<Element> UserElements = rootElement.elements("user");
		//3.遍历每个user,以便确保新注册的username,email是未使用过的
		for (Element element : UserElements) {
			if(element.elementText("username").equals(user.getUsername()))
				return USERNAME_EXIST;
			if(element.elementText("email").equals(user.getEmail()))
				return EMAIL_EXIST;
		}
		//4.到此说明用户名，邮箱都是未使用过的，就将其加入文件，
			//4.1创建用户根标签：user
		Element userEle = DocumentHelper.createElement("user");
		
			//4.2创建username标签,并赋值
		Element usernameEle = DocumentHelper.createElement("username");
		usernameEle.setText(user.getUsername());
		
			//4.3创建password标签,并赋值
		Element passwordEle = DocumentHelper.createElement("password");
		passwordEle.setText(user.getPassword());
		
			//4.3创建email标签,并赋值
		Element emailEle = DocumentHelper.createElement("email");
		emailEle.setText(user.getEmail());
		
			//4.4将创建的各个标签加入到user根标签中
		userEle.add(usernameEle);
		userEle.add(passwordEle);
		userEle.add(emailEle);
			//4.5将创建的user标签加入到根标签users中：
		rootElement.add(userEle);
		
		//5.将上述内存中的文件写回到原文件中：
		XMLWriter xmlWriter =null;
		OutputFormat format = OutputFormat.createPrettyPrint();
		try {
			xmlWriter = new XMLWriter(new FileOutputStream("d:\users.xml"),format);
			xmlWriter.write(document);
			xmlWriter.close();
		}catch (Exception e) {
			e.printStackTrace();
		}
		
		return SUCCESS;
		
	}
	public User login(User user) {
		SAXReader saxReader = new SAXReader();
		Document document = null;
		try {
			document = saxReader.read("d://users.xml");
		} catch (Exception e) {
			e.printStackTrace();
		}
		Element rootElement = document.getRootElement();
		List<Element> elements = rootElement.elements("user");
		for (Element element : elements) {//如果存在,将此用户，如果不存在，返回空，
			if(element.elementText("username").equals(user.getUsername()) &&
					element.elementText("password").equals(user.getPassword())){
				return user;
			}
		}
		return null;
		
	}
}


五：登陆页面：login.jsp:

提供让用户填写登陆信息的页面

将用户填写的信息发给LoginServlet：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
	<font color="green"><h3>${message }</h3></font>
	<%="fuck you, plealse login!" %>
	<form action="${pageContext.request.contextPath }/servlet/LoginServlet" method="post">
		<table>
			<tr>
				<td>用户名：</td>
				<td><input type="text" name="username" value="${cookie.username.value }"></td>
			</tr>
			<tr>
				<td>密码：</td>
				<td><input type="password" name="password" value="${cookie.password.value }"></td>
			</tr>
			<tr>
				<td>
					<input type="checkbox" name="remember" value="off">记住用户名与密码
				</td>
			</tr>
			
			<tr>
				<td><input type="submit" value="登陆"></td>
			</tr>
		</table>
	</form>
</body>
</html>


六：LoginServlet,查看用户登陆时所填写的信息是否与数据库文件中的相应数据符合，
若符合，则显示登陆成功，若不符合，则请求转发到登陆页面：

package com.itcode.controller;

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;

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 org.apache.commons.beanutils.BeanUtils;

import com.itcode.model.User;
import com.itcode.model.UserOperator;

public class LoginServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		User user = new User();
		try {
			BeanUtils.populate(user, request.getParameterMap());
		} catch (IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InvocationTargetException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		UserOperator userOperator = new UserOperator();
		User existUser = userOperator.login(user);
		if(existUser == null){
			response.getWriter().println("用户名或密码不正确，请重新输入！");
			request.getRequestDispatcher("/login.jsp").forward(request, response);
		}else{//登陆成功后，跳转到首页。在首 页要判断用户是否已经登陆
			request.getSession().setAttribute("existUser",existUser);
			if("on".equals(request.getParameter("remember"))){
				//1.将用户名写进cookie
//				Cookie usernameCookie = new Cookie("username",request.getParameter("username"));
				Cookie usernameCookie = new Cookie("username",existUser.getUsername());
				usernameCookie.setMaxAge(60*12);
				usernameCookie.setPath("/");
				response.addCookie(usernameCookie);
				System.out.println("-----------22----------------");
				//2.将密码写进cookie
//				Cookie passwordCookie = new Cookie("password",request.getParameter("password"));
				Cookie passwordCookie = new Cookie("password",existUser.getPassword());
				passwordCookie.setMaxAge(60*12);
				passwordCookie.setPath("/");
				response.addCookie(passwordCookie);
				System.out.println("-----------44----------------");
			}
			response.sendRedirect("/user/index.jsp");
		}
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		doGet(request, response);
	}

}



七：注销成功的实现：

在登录成功后的页面写个注销的超链接，链接到注销Servlet，LogoutServlet.java

package com.itcode.controller;

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 LogoutServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
//		request.getSession().removeAttribute("existUser");
		request.getSession().invalidate();
		response.getWriter().println("fuck you have logout!");
		response.sendRedirect("/user/index.jsp");
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		doGet(request, response);
	}

}



八：为了显示效果，写个首页：


 
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
    <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
	<font color="red"><h2>这是首页</h2></font>
	<hr>
	<c:if test="${empty existUser }">
		你好，你还没有登陆！<br/>
		<a href="${pageContext.request.contextPath }/login.jsp">去登陆</a><br/>
		<a href="${pageContext.request.contextPath }/regist.jsp">去注册</a><br/>
	</c:if>
	<c:if test="${not empty existUser }">
		${existUser.username },你好，你已经成功登陆！<br/>
		<a href="${pageContext.request.contextPath }/servlet/LogoutServlet">去注销</a>
	</c:if>
</body>
</html>



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原文地址：https://www.cnblogs.com/suncoolcat/p/3283649.html