使用 Cookies 的 Servlet 登录和登出示例

17 Mar 2025 | 阅读 2 分钟

Cookie 是一种存储在客户端的信息。

在上一页，我们学习了许多关于 cookie 的知识，例如如何创建 cookie、如何删除 cookie、如何获取 cookie 等。

在这里，我们将创建一个使用 servlet cookies 的登录和登出示例。

在这个例子中，我们创建了 3 个链接：登录、登出和个人资料。用户在登录之前无法进入个人资料页面。如果用户已登出，则需要重新登录才能访问个人资料。

在这个应用程序中，我们创建了以下文件。

index.html
link.html
login.html
LoginServlet.java
LogoutServlet.java
ProfileServlet.java
web.xml

文件：index.html

<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Servlet Login Example</title>
</head>
<body>

<h1>Welcome to Login App by Cookie</h1>
<a href="login.html">Login</a>|
<a href="LogoutServlet">Logout</a>|
<a href="ProfileServlet">Profile</a>

</body>
</html>

文件：link.html

<a href="login.html">Login</a> |
<a href="LogoutServlet">Logout</a> |
<a href="ProfileServlet">Profile</a>
<hr>

文件：login.html

<form action="LoginServlet" method="post">
Name:<input type="text" name="name"><br>
Password:<input type="password" name="password"><br>
<input type="submit" value="login">
</form>

文件：LoginServlet.java

package com.javatpoint;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginServlet extends HttpServlet {
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
                           throws ServletException, IOException {
		response.setContentType("text/html");
		PrintWriter out=response.getWriter();
		
		request.getRequestDispatcher("link.html").include(request, response);
		
		String name=request.getParameter("name");
		String password=request.getParameter("password");
		
		if(password.equals("admin123")){
			out.print("You are successfully logged in!");
			out.print("<br>Welcome, "+name);
			
			Cookie ck=new Cookie("name",name);
			response.addCookie(ck);
		}else{
			out.print("sorry, username or password error!");
			request.getRequestDispatcher("login.html").include(request, response);
		}
		
		out.close();
	}

}

文件：LogoutServlet.java

package com.javatpoint;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LogoutServlet extends HttpServlet {
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
                        throws ServletException, IOException {
		response.setContentType("text/html");
		PrintWriter out=response.getWriter();
		
		
		request.getRequestDispatcher("link.html").include(request, response);
		
		Cookie ck=new Cookie("name","");
		ck.setMaxAge(0);
		response.addCookie(ck);
		
		out.print("you are successfully logged out!");
	}
}

文件：ProfileServlet.java

package com.javatpoint;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ProfileServlet extends HttpServlet {
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
                          throws ServletException, IOException {
		response.setContentType("text/html");
		PrintWriter out=response.getWriter();
		
		request.getRequestDispatcher("link.html").include(request, response);
		
		Cookie ck[]=request.getCookies();
		if(ck!=null){
		 String name=ck[0].getValue();
		if(!name.equals("")||name!=null){
			out.print("<b>Welcome to Profile</b>");
			out.print("<br>Welcome, "+name);
		}
		}else{
			out.print("Please login first");
			request.getRequestDispatcher("login.html").include(request, response);
		}
		out.close();
	}
}

文件：web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  
  <servlet>
    <description></description>
    <display-name>LoginServlet</display-name>
    <servlet-name>LoginServlet</servlet-name>
    <servlet-class>com.javatpoint.LoginServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>LoginServlet</servlet-name>
    <url-pattern>/LoginServlet</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>ProfileServlet</display-name>
    <servlet-name>ProfileServlet</servlet-name>
    <servlet-class>com.javatpoint.ProfileServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>ProfileServlet</servlet-name>
    <url-pattern>/ProfileServlet</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>LogoutServlet</display-name>
    <servlet-name>LogoutServlet</servlet-name>
    <servlet-class>com.javatpoint.LogoutServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>LogoutServlet</servlet-name>
    <url-pattern>/LogoutServlet</url-pattern>
  </servlet-mapping>
</web-app>

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