P17 Session

Session与Cookie很相似。

Cookie是将内容存在客户的机器上

Session是将内容存在服务器上，同时Session可以存对象（存类）。 

制作一个Session 

package com.Li.servlet;

import com.Li.pojo.Persion;
//之所以能连起来是因为Session能做Context的内容
import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.io.IOException;
//创建Session
public class SessionDemo01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

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

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

        //给Session中存东西(字符)
        session.setAttribute("name", new Persion("蔡勾", 1));


        //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："+sessionId);
        }else {
            resp.getWriter().write("session已经存在。ID："+sessionId);
        }
        //Session创建的时候做了什么
        Cookie cookie = new Cookie("JSESSIONID", sessionId);
        resp.addCookie(cookie);
    }

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

将Session中的内容取出来并显示 

package com.Li.servlet;

import com.Li.pojo.Persion;

import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.io.IOException;
//拿到Demo01的session并且输出到控制台
public class SessionDemo02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

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

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

        Persion name = (Persion) session.getAttribute("name");

        System.out.println(name);

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

实现手动清除Session 

package com.Li.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;

//注销Session（手动）
public class SessionDemo03 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        HttpSession session = req.getSession();
        session.removeAttribute("name");
        session.invalidate();
    }

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

创建测试所需要的对象 

package com.Li.pojo;

public class Persion {
    private String name;
    private int age;

    public Persion(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 "Persion{" +
                "name='" + name + ''' +
                ", age=" + age +
                '}';
    }
}

设置自动清空Session

在web.xml中

    

        1