使用Servlet HttpSession的登录和登出示例

我们可以在HttpSession实例上绑定对象，并使用setAttribute和getAttribute方法获取对象。

在上一页中，我们已经了解了什么是HttpSession，如何存储和从会话对象中获取数据等内容。

在这里，我们将创建一个不使用数据库代码的真实世界登录和登出应用。我们假设密码是admin123。

在这个示例中，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访问个人资料页面。如果用户已登出，他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>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>

输出

如果您再次点击个人资料链接，您需要先登录。

Java Servlet教程—使用Servlet HttpSession的登录和登出示例

使用Servlet HttpSession的登录和登出示例

输出

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