Servlet HttpSession 登录和注销示例

17 Mar 2025 | 阅读 2 分钟

我们可以将对象绑定到 HttpSession 实例上，并使用 setAttribute 和 getAttribute 方法获取这些对象。

在上一页，我们学习了什么是 HttpSession，如何从会话对象存储和获取数据等。

在这里，我们将创建一个真实的登录和注销应用程序，而无需使用数据库代码。我们假设密码是 admin123。

访问这里获取仅使用 Cookie 的登录和注销应用程序使用 Cookie 的 Servlet 登录和注销示例

在此示例中，我们创建了 3 个链接：登录、注销和个人资料。用户在登录之前无法进入个人资料页面。如果用户已注销，则需要重新登录才能访问个人资料。

在此应用程序中，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>Login App using HttpSession</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

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
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("Welcome, "+name);
		HttpSession session=request.getSession();
		session.setAttribute("name",name);
		}
		else{
			out.print("Sorry, username or password error!");
			request.getRequestDispatcher("login.html").include(request, response);
		}
		out.close();
	}
}

文件：LogoutServlet.java

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
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);
			
			HttpSession session=request.getSession();
			session.invalidate();
			
			out.print("You are successfully logged out!");
			
			out.close();
	}
}

文件：ProfileServlet.java

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
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);
		
		HttpSession session=request.getSession(false);
		if(session!=null){
		String name=(String)session.getAttribute("name");
		
		out.print("Hello, "+name+" Welcome to Profile");
		}
		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>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>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>LogoutServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>LogoutServlet</servlet-name>
    <url-pattern>/LogoutServlet</url-pattern>
  </servlet-mapping>
</web-app>

下载此示例（使用 Eclipse IDE 开发）