欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页  >  IT编程

Java中Session的详解

程序员文章站 2022-06-23 12:12:43
目录1.什么是session:服务器会给每一个用户(浏览器)创建一个session对象一个session独占一个浏览器,只要浏览器不关闭,这个session就一直存在session称为会话控制,存储用...

1.什么是session:

服务器会给每一个用户(浏览器)创建一个session对象

一个session独占一个浏览器,只要浏览器不关闭,这个session就一直存在

session称为会话控制,存储用户会话所需的属性和配置信息,这样,用户在应用程序的web页面跳转时,存储在session对象中的用户信息不会丢掷,而是在整个用户会话中一直保持下去

2.session的经典应用场景:

一个用户登陆后,访问该网站的其他网页时,一直处于登录状态

保存购物车信息等等

3.session中常用的方法

getid():获取session的唯一标识

getservletcontext():代表整个web服务

getattribute(string):获取session的节点,比如你在其中一个servlet中通过setattribute(string,object)配置了相关的session信息,然后通过另一个servlet获取这个servlet中的session信息,就要用到getattribute(string)这个方法

setattribute(string,object):设置session节点

removeattribute(string):一出一个session节点

isnew():判断一个session是否是一个新的session

invalidate():注销session的

4.举例

例1:创建一个session并获取到session的id,判断这个session是否是新的session

步骤1:新建一个maven项目,使用webapp模板

步骤2:在java文件夹下创建一个com.xiaoma.servlet.sessiondemo01的类,编写servlet类文件

package com.xiaoma.servlet;
import com.xiaoma.pojo.person;
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 sessiondemo01 extends httpservlet {
     @override
     protected void doget(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
         //解决中文乱码
         resp.setheader("content-type","text/html;charset=utf-8");
         //得到session
         httpsession session = req.getsession();
         //通过setattribute方法向session中存放信息
         session.setattribute("name","小马");
         //获取session相关信息,包括id,是否是新的session等
         string sessionid = session.getid();
         if(session.isnew()) {
             resp.getwriter().write("创建session成功,id为:" + sessionid);
         }else{
             resp.getwriter().write("session已经存在了,id为:" + sessionid);
         }
     }
     @override
     protected void dopost(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
         doget(req, resp);
     }
 }

步骤3:配置xml文件

<servlet>
         <servlet-name>sessiondemo01</servlet-name>
         <servlet-class>com.xiaoma.servlet.sessiondemo01</servlet-class>
     </servlet>
     <servlet-mapping>
         <servlet-name>sessiondemo01</servlet-name>
         <url-pattern>/s1</url-pattern>
     </servlet-mapping>

例2:从一个servlet中读取另一个servlet中的session信息

步骤1:在java文件夹下创建一个com.xiaoma.servlet.sessiondemo01的类,编写servlet类文件

  package com.xiaoma.servlet;
  import com.xiaoma.pojo.person;
  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 sessiondemo01 extends httpservlet {
     @override
     protected void doget(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
         //解决中文乱码
         resp.setheader("content-type","text/html;charset=utf-8");
         //得到session
         httpsession session = req.getsession();
         //通过setattribute方法向session中存放信息
         session.setattribute("name","小马");
         //获取session相关信息,包括id,是否是新的session等
         string sessionid = session.getid();
         if(session.isnew()) {
             resp.getwriter().write("创建session成功,id为:" + sessionid);
         }else{
             resp.getwriter().write("session已经存在了,id为:" + sessionid);
        }
     }
     @override
     protected void dopost(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
         doget(req, resp);
     }
 }

步骤2:在java文件夹下创建一个com.xiaoma.servlet.sessiondemo02的类,编写另一个用来读取的servlet类,通过sessiondemo02来读取sessiondemo01中的session信息

 package com.xiaoma.servlet;
  import com.xiaoma.pojo.person;
  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 sessiondemo02 extends httpservlet {
    @override
     protected void doget(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
         //解决中文乱码
        resp.setheader("content-type","text/html;charset=utf-8");
         //得到session
         httpsession session = req.getsession();
         string name=(string) session.getattribute("name");
         resp.getwriter().write(name);
     }
     @override
     protected void dopost(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
         super.dopost(req, resp);
     }
 }

步骤3:配置xml文件

     <servlet>
         <servlet-name>sessiondemo02</servlet-name>
        <servlet-class>com.xiaoma.servlet.sessiondemo02</servlet-class>
     </servlet>
     <servlet-mapping>
         <servlet-name>sessiondemo02</servlet-name>
         <url-pattern>/s2</url-pattern>
     </servlet-mapping>

例3:session中还可以存放对象信息

步骤1:在java文件夹下创建一个com.xiaoma.pojo.person的类,编写我们的实体类

 package com.xiaoma.pojo;
  public class person {
      private string name;
      private int age;
      public person() {
      }
     public person(string name, int age) {
         this.name = name;
         this.age = age;
     }
     public string getname() {
         return name;
     }
     public void setname(string name) {
         this.name = name;
     }
      public int getage() {
         return age;
     }
     public void setage(int age) {
         this.age = age;
     }
     @override
     public string tostring() {
         return "person{" +
                "name='" + name + '\'' +
                 ", age=" + age +
                 '}';
     }
 }

步骤2:在java文件夹下创建一个com.xiaoma.servlet.sessiondemo01的类,编写servlet类文件

  package com.xiaoma.servlet;
  import com.xiaoma.pojo.person;
  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 sessiondemo01 extends httpservlet {
     @override
     protected void doget(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
        //解决中文乱码
         resp.setheader("content-type","text/html;charset=utf-8");
        //得到session
         httpsession session = req.getsession();
         //通过setattribute方法向session中存放信息
         session.setattribute("name",new person("小马",18));
         //获取session相关信息,包括id,是否是新的session等
         string sessionid = session.getid();
         if(session.isnew()) {
             resp.getwriter().write("创建session成功,id为:" + sessionid);
         }else{
             resp.getwriter().write("session已经存在了,id为:" + sessionid);
         }
     }
     @override
     protected void dopost(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
         doget(req, resp);
     }
 }

步骤3:在java文件夹下创建一个com.xiaoma.servlet.sessiondemo02的类,编写另一个servlet类文件,用来读取sessiondemo01中的session对象信息

 package com.xiaoma.servlet;
  import com.xiaoma.pojo.person;
  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 sessiondemo02 extends httpservlet {
     @override
     protected void doget(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
         //获取session中的person对象
         //解决中文乱码
         resp.setheader("content-type","text/html;charset=utf-8");
         //得到session
         httpsession session = req.getsession();
         person person=(person) session.getattribute("name");
         resp.getwriter().write(person.tostring());
     }
     @override
     protected void dopost(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
         super.dopost(req, resp);
     }
 }

步骤4:编写xml文件,与上同理

例4:注销session(注销session有两种方式,一种是通过removeattribute(string)方法,另一种是通过xml配置文件)

第一种,通过removeattribute(string)方法,这种方式是使session手动过期

  package com.xiaoma.servlet;
  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 sessiondemo03 extends httpservlet {
     @override
     protected void doget(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
         //得到session
         httpsession session = req.getsession();
         //手动注销session
        session.removeattribute("name");
         session.invalidate();
     }
     @override
     protected void dopost(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
         super.dopost(req, resp);
     }
}

第二种,通过xml文件的方法,这种方式是时session自动过期

     <!--设置session的存活时间-->
     <session-config>
         <!--以分钟为单位-->
         <session-timeout>1</session-timeout>
     </session-config>

5.session与cookie的区别

  ·(1)cookie是吧用户的数据写给浏览器,浏览器保存(可以保存多个)

  ·(2)session是把用户的数据写给用户独占的session中,服务器保存(保存重要信息,避免浪费服务器资源)

  ·(3)session是由服务器创建的