Servlet中的Session使用方法

步骤

• 获取 session 对象
• 通过 setAttribute 写入 session
• 获取 session 的值
• session 销毁（手动销毁和自动销毁）

设置 session

package com.demo;

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;
import java.io.PrintWriter;

public class SetSessionDemo extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 设置字符集
        req.setCharacterEncoding("utf-8");
        resp.setContentType("text/html; charset=utf-8");

        PrintWriter writer = resp.getWriter();

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

        // 写入 session
        session.setAttribute("GoodsDetail", " 商品详情 ");

        // 获取 session id
        String id = session.getId();

        // 判断 session 否新建
        if (session.isNew()) {writer.write("session 创建成功, session id 为: " + id);
        } else {writer.write("session 已经在服务器中存在了，ID: " + id);
        }
    }

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

获取 session 中的值

package com.demo;

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 GetSessionDemo extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 设置字符集
        req.setCharacterEncoding("utf-8");
        resp.setContentType("text/html; charset=utf-8");

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

        String goodsDetail = (String) session.getAttribute("GoodsDetail");

        resp.getWriter().write(goodsDetail);
    }

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

session 销毁

手动

package com.demo;

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 DelSessionDemo extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {HttpSession session = req.getSession();

        session.removeAttribute("GoodsDetail");

        session.invalidate();}

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

自动过期销毁

    <session-config>
        <!--  设置 session 默认的失效时间, 以分钟为单位 -->
        <session-timeout>1</session-timeout>
    </session-config>

web.xml

<servlet>
        <servlet-name>setSessionDemo</servlet-name>
        <servlet-class>com.demo.SetSessionDemo</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>setSessionDemo</servlet-name>
        <url-pattern>/set/session/demo</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>getSessionDemo</servlet-name>
        <servlet-class>com.demo.GetSessionDemo</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>getSessionDemo</servlet-name>
        <url-pattern>/get/session/demo</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>delSessionDemo</servlet-name>
        <servlet-class>com.demo.DelSessionDemo</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>delSessionDemo</servlet-name>
        <url-pattern>/del/session/demo</url-pattern>
    </servlet-mapping>