Session(重点)

Session和cookie的区别：

　　1.Cookie是把用户的数据写给用户的浏览器，浏览器保存（可以保存多个）

　　2.Session把用户代的数据写到用户独占的session中，服务端保存（保存重要信息，减少服务资源浪费）

　　3.Session对象由服务器创建

 

获取sessionId(sessionid是以cookie形式传递)

package com.king.servlet;

import com.king.pojo.Person;

import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.io.IOException;

public class SessionDemo01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //解决乱码问题
        resp.setCharacterEncoding("utf-8");
        req.setCharacterEncoding("utf-8");
        resp.setContentType("text/html;charset=utf-8");

        //得到Session
        HttpSession session = req.getSession();


        //给Session中存东西
        session.setAttribute("name",new Person("king",18));

        //获取session的ID
        String sessionId = session.getId();

        //判断session是不是新创建的
        if (session.isNew()){
            resp.getWriter().write("session创建成功，ID:D:"+sessionId);
        }else{resp.getWriter().write("session已经存在，ID:D:"+sessionId);}

        //Session创建的时候做了什么事情
        //Cookie cookie = new Cookie("JSESSIONID", sessionId);
        //resp.addCookie(cookie);
        //总结：session的id是以cookie形式传递的


   }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

 

获得session存的数据

package com.king.servlet;

import com.king.pojo.Person;

import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.io.IOException;

public class SessionDemo02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //解决乱码问题
        resp.setCharacterEncoding("utf-8");
        req.setCharacterEncoding("utf-8");
        resp.setContentType("text/html;charset=utf-8");

        //得到Session
        HttpSession session = req.getSession();

        Person person = (Person) session.getAttribute("name");

        System.out.println(person.toString());
        System.out.println(person);
        resp.getWriter().write(person.toString());

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

实体类（Person）

package com.king.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 int getAge() {
        return age;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

 

手动注销session

package com.king.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 {
        HttpSession session = req.getSession();
        session.removeAttribute("name");
        //手动注销session
        session.invalidate();
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

 

web.xml

<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_4_0.xsd"
         version="4.0"
         metadata-complete="true">

    <servlet>
        <servlet-name>CookieDemo01</servlet-name>
        <servlet-class>com.king.servlet.CookieDemo01</servlet-class>
    </servlet>
    
    <servlet-mapping>
        <servlet-name>CookieDemo01</servlet-name>
        <url-pattern>/c1</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>CookieDemo02</servlet-name>
        <servlet-class>com.king.servlet.CookieDemo02</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>CookieDemo02</servlet-name>
        <url-pattern>/c2</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>SessionDemo01</servlet-name>
        <servlet-class>com.king.servlet.SessionDemo01</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>SessionDemo01</servlet-name>
        <url-pattern>/s1</url-pattern>
    </servlet-mapping>


    <servlet>
        <servlet-name>SessionDemo02</servlet-name>
        <servlet-class>com.king.servlet.SessionDemo02</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>SessionDemo02</servlet-name>
        <url-pattern>/s2</url-pattern>
    </servlet-mapping>


    <servlet>
        <servlet-name>SessionDemo03</servlet-name>
        <servlet-class>com.king.servlet.SessionDemo03</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>SessionDemo03</servlet-name>
        <url-pattern>/s3</url-pattern>
    </servlet-mapping>

    <!--设置session默认失效时间-->
    <session-config>
        <!--设置1分钟后session自动失效-->
        <session-timeout>1</session-timeout>
    </session-config>

</web-app>