重定向到servlet

时间：2017-07-25 06:40:43

标签： java html google-app-engine servlets url-redirection

您好我使用servlet做了简单的Web应用程序，根据可用的会话提供登录和欢迎页面。我附上了以下代码，

每当用户键入URL http://localhost:8888/时，他必须转到dashboard servlet（如web.xml中所述）

在dashboard servlet，中选中会话

如果会话可用，那么我将提供welcome.html页面， 否则我会重定向到login servlet

在login servlet，

GET方法， 如果用户有会话，我会重定向到dashboard servlet 否则我会转发welcome.html页面

用户输入信息后，会将信息发布到login servlet（即POST）

POST方法， 我将从请求中获取用户名和密码，我将检查值为admin和password

如果是，则创建会话并将用户重定向到dashboard servlet 否则我会将用户重定向到login servlet（GET方法）

Web应用程序应该只需要这两个URL，

（1）http://localhost:8888/ （2）http://localhost:8888/login

用户不应该知道我为他们服务的页面类型（html或jsp），但我只需要提供HTML页面（这是我的要求）

当我启动应用引擎时，首先将请求发送到仪表板，然后将其重定向到login servlet，然后再次为仪表板制作循环，

我使用System.out.println()来跟踪我的输出

的控件 
The admin console is running at http://localhost:8888/_ah/admin
Jul 25, 2017 11:12:55 AM com.google.appengine.tools.development.DevAppServerImpl doStart
INFO: Dev App Server is now running
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
login servlet get method
request no session
-->dashboard servlet
get method
no session,
  

问题：

怎样才能解决这个问题？

如果我将web.xml中的网址格式更改为<url-pattern>/index</url-pattern>，并且在重定向到/的servlet中，我将/index更改为dashboard servlet它是工作正常，但我怎样才能利用＆＃34; /＆＃34; for servlet

我已附上以下源代码，

信息中心servlet

包servlet; 

import java.io.IOException;

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

@SuppressWarnings("serial")
public class DashboardServlet extends HttpServlet {
    public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("-->dashboard servlet");
        System.out.println("get method");
        HttpSession session = req.getSession(false);
        if (session != null) {          
            System.out.println("session is available");
            req.getRequestDispatcher("/WEB-INF/welcome.html").forward(req, resp);
        } else {
            System.out.println("no session,");
            resp.sendRedirect("/login");
        }
    }
}

登录Servlet 

package servlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

@SuppressWarnings("serial")
public class LoginServlet extends HttpServlet {
    public void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("-->>>login servlet post method");
        String name = req.getParameter("username");
        String password = req.getParameter("password");
        if (name.equals("admin") && password.equals("password")) {
            HttpSession session = req.getSession();
            session.setAttribute("sessionUserName", name);
            resp.sendRedirect("/");

        } else {
            resp.sendRedirect("/login");
        }
    }

    public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        System.out.println("login servlet get method");
        HttpSession session = req.getSession(false);
        if (session != null) {
            System.out.println("request with session");
            resp.sendRedirect("/");
        } else {
            System.out.println("request no session");
            req.getRequestDispatcher("/WEB-INF/login.html").forward(req, resp);
        }

    }
}

的web.xml 

<web-app>
    <servlet>
        <servlet-name>Login</servlet-name>
        <servlet-class>servlet.LoginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>Login</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>Dashboard</servlet-name>
        <servlet-class>servlet.DashboardServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>Dashboard</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>

应用服务引擎-web.xml中 

<?xml version="1.0" encoding="utf-8"?>
<appengine-web-app xmlns="http://appengine.google.com/ns/1.0">
    <application></application>
    <version>1</version>
    <threadsafe>true</threadsafe>
    <system-properties>
        <property name="java.util.logging.config.file" value="WEB-INF/logging.properties" />
    </system-properties>
    <sessions-enabled>true</sessions-enabled>
</appengine-web-app>

的login.html 

<!DOCTYPE html>
<html>
<head>
<title>Insert title here</title>
</head>
<body>
    <form action="/login" method="post">
        User name :<input type='text' name='username'>Password :<input
            type='password' name='password'><input type='submit'
            value='Submit'>
    </form>
</body>
</html>

welcome.html 

<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>welcome here
</body>
</html>

谢谢，

1 个答案:

答案 0 :(得分：1)

您不应仅检查会话是否为空。您应该将类​​似'logged_in'的值作为属性放入会话中。然后，控制它以决定路由的位置。

更新

作为一种快速解决方案，将LoginServlet内的doGet路由到doPost并更改doPost，如下所示：

   public void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        System.out.println("login servlet get method");
        HttpSession session = req.getSession(false);
        if (session != null && session.getAttribute("sessionUserName")!=null) {
            System.out.println("request with session");
            resp.sendRedirect("/");
        } else {

            String name = req.getParameter("username");
            String password = req.getParameter("password");
            if (name.equals("admin") && password.equals("password")) {
                session = req.getSession();
                session.setAttribute("sessionUserName", name);
                resp.sendRedirect("/");

            } else {
               System.out.println("request no session");
                req.getRequestDispatcher("/WEB-INF/login.html").forward(req, resp);
            }

        }

    }
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