J2EE--Session

1. 为什么要使用Session？
2. 怎样使用Session？
3. Session和Cookie的区别？

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1.为什么要使用Session？

Session属于服务器端存储数据，不限制存储的内容，任意类型均可存储。

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2.怎样使用Session？

2.1 Session常用方法

用法	说明
HttpSession session = request.getSession()	获取HttpSession对象
Object getAttribute(String name)	使用HttpSession对象
void setAttribute(String name, Object value)	设置HttpSession对象
void removeAttribute(String name)	删除HttpSession对象

2.2 Session完整示例

示例代码

@WebServlet("/session1")
public class SessionDemo1 extends HttpServlet {

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        HttpSession httpSession = req.getSession();

        httpSession.setAttribute("msg","hello session");

    }

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

@WebServlet("/session2")
public class SessionDemo2 extends HttpServlet {

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        HttpSession httpSession = req.getSession();

        System.out.println(httpSession.getAttribute("msg"));

    }

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

效果展示

image.png

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3. Session和Cookie的区别？

1. session存储数据在服务器端，Cookie在客户端
2. session没有数据大小限制，Cookie有
3. session数据安全，Cookie相对于不安全