Session learning diary 1

  Catalog

One 、Session object

1.1 Session summary

1.2 Session principle

1.3 Session Use

1.4 Session And Request Application difference

1.5 Session Life cycle of

Two 、 Browser disable Cookie Solution

2.1 Browser disable Cookie The consequences of

2.2 URL rewrite

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One 、Session object

1.1 Session summary

1、Session Used to record the user's status . Session It means in a For a while , Single client and Web A series of related interactive processes of the server .

2、 In a Session in , Customers may request access to the same resource multiple times , It is also possible to request access to various server resources .

1.2 Session principle

1、 The server will assign one for each session Session object

2、 Multiple requests from the same browser , Belong to the same session (Session)

3、 First use to Session when , The server will automatically create Session, And create Cookie Storage Sessionld Of ID Send back to client

Be careful ：session It is created by the server .

1.3 Session Use

1、Session Scope ： Have space to store data , The scope is valid for one session

（1） A session is multiple requests sent using the same browser . One Once the browser closes , Ends the session

（2） Data can be stored in Session in , Get anywhere in a session

（3） Can transfer any data （ Basic data type 、 object 、 aggregate 、 Array ）

2、 obtain Session

HttpSession session = request.getSession();
System.out.println("Id：" + session.getID());  //  The only mark 

Code ：

package com.ha.session;

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

public class SessionServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();
        System.out.println(session.getId());
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
                      http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
  version="3.1"
  metadata-complete="true">

  <servlet>
    <servlet-name>ss</servlet-name>
    <servlet-class>com.ha.session.SessionServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>ss</servlet-name>
    <url-pattern>/ss</url-pattern>
  </servlet-mapping>

</web-app>

If you close the browser , Revisit , To get the sessionID It's different , Prove that after the last session session It was destroyed

3、Session Save the data

settrbute( Property name , 0bject);  Save data to session in

session.setAttribute("key", value);  // Stored in... As key value pairs session Scope .

4、Session get data

getAttribute( Property name );  obtain session Data in the

session.getAttribute("key");  // adopt String Type of key visit 0bject Type of value

5、Session Remove data

removeAtribute( Property name );  from session Delete data from
session.removeAttribute("key");  // Remove by key session Value in scope

6、 Code

package com.ha.session;

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

public class SessionServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1. adopt request Object acquisition Session object 
        HttpSession session = request.getSession();

        //2. Use session Save the data 
        session.setAttribute("username","HuAn");
        session.setAttribute("password","123456");
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}

package com.ha.session;


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

public class GetValueServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1. adopt request obtain session object 
        HttpSession session = request.getSession();

        String username = (String)session.getAttribute("username");
        String password = (String)session.getAttribute("password");

        System.out.println(" from session Got ："+username);
        System.out.println(" from session Got ："+password);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}

 

  If you show it again session I executed this paragraph before , Then you can't get username 了 , Start with removal , All access to username All the contents obtained are NULL

1.4 Session And Request Application difference

request It's one Valid requests , Request change , be request change

session It's one Session is valid , Browser changes , be session change

Code ： 

modify SessionServlet.java

modify GetValueServlet.java

  visit ss Jump to gv

1.5 Session Life cycle of

Start ： The first time I used Session The request generated , Create Session

end ：

         Browser closed , Failure

        Session Overtime , Failure
                session.setMaxlnactiveIntervalseconds);  // Set the maximum effective time （ Company ： second ）

         Hand destroy , Failure
                session.invalidate();  // Log in to exit 、 Cancellation

Visit the one above again Java file , For the second Java The generated browser closes when it closes session The destruction time of has been modified .

The following code , Every time I get session It's all different .

Two 、 Browser disable Cookie Solution

2.1 Browser disable Cookie The consequences of

The server is by default , Will use Cookie The way to sessionID Send it to the browser , If the user prohibits Cookie be sessionlD Will not be saved by the browser , At this time, the server can use such as URL Rewrite this way to send sessionID.

2.2 URL rewrite

When the browser accesses an address on the server , No longer use the original address , Instead, use a rewritten address （ That is, add... After the original address sessionID）.

Splicing , Then jump to the code ：