69期-Java SE-046_JSP-3

旧城等待， 2021-12-03 15:45 251阅读 0赞

### session
    
    setAttribute
    
    getAttribute
    
    removeAttribute
    
    invalidate            //设置 session 失效，当用户执行退出登录时，调用该方法
    
    
    
    ### Cookie
    
    Cookie 时服务端在 HTTP 响应过程中附带传送给浏览器的一个文本文件，一旦浏览器保存了某个 Cookie，那么在以后的每次访问中都会将这个 Cookie 传递，服务端在做响应的时候会再次将 Cookie 传给浏览器，以此类推，如此 Cooki 就可以在客户端和服务端之间来回传递，从而实现数据交互的功能。
    
    Cookie 常用方法
    
    - new Cookie(String name,String value)    创建一个 Cookie 对象，用键值对的形式来存储数据
    
    ```jsp
    Cookie cookie = new Cookie("age","22");
    response.addCookie(cookie);
    ```
    
    - request.getCookies()                         获取 request 中的所有 Cookie
    
    - void setMaxAge(int age)                   设置 Cookie 的有效期，以秒为单位
    - int getMaxAge()                                  获取 Cookie 的有效期
    - void setValue(String value)               修改 Cookie 的 value 值
    - String getName()                                获取 Cookie 的 name 值
    - String getValue()                                 获取 Cookie 的 value 值
    
    
    
    ### Session 和 Cookie 的区别
    
    Session 保存在服务端，Cookie 保存在客户端。
    
    Session 存储的数据类型 Object，Cookie 只能存储 String
    
    Session 会随着会话的结束而销毁，Cookie 可长期保存在客户端浏览器中
    
    Session 保存重要信息，Cookie 保存不重要的信息
    
    
    
    ### JSP 内置对象作用域
    
    page 作用域：对应的内置对象是 pageContext
    
    request 作用域：对应的内置对象是 request
    
    session 作用域：对应的内置对象是 session
    
    application 作用域：对应的内置对象是 application
    
    page 作用域只在当前页面有效，对应 JSP。
    
    request 作用域在同一次请求内有效，对应请求。
    
    session 作用域在同一次会话中有效，对应会话。
    
    application 作用域对应的是整个 Web 应用，只要 Tomcat 不重启，application 就可用，对应 Tomcat。

![1603260-20190713234230994-1777442014.png][]

LoginServlet.java

package com.southwind.controller;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    import java.io.IOException;
    
    @WebServlet("/login.do")
    public class LoginServlet extends HttpServlet {
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            String username = req.getParameter("username");
            String password = req.getParameter("password");
            if(username.equals("zhangsan")&&password.equals("123")){
                //用户信息保存到session中
                HttpSession session = req.getSession();
                session.setAttribute("username",username);
                resp.sendRedirect("index.jsp");
            }else{
                resp.sendRedirect("login.jsp");
            }
        }
    }

LogoutServlet.java

![1603260-20190713234348099-703776325.png][]

cookie.jsp

<%--
      Created by IntelliJ IDEA.
      User: southwind
      Date: 2019-07-09
      Time: 20:40
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>Title</title>
    </head>
    <body>
        <%
            //创建 Cookie
            Cookie cookie = new Cookie("age","22");
            response.addCookie(cookie);
        %>
    </body>
    </html>

count.jsp

<%--
      Created by IntelliJ IDEA.
      User: southwind
      Date: 2019-07-09
      Time: 21:47
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>Title</title>
    </head>
    <body>
        <%
            Integer num = (Integer) application.getAttribute("num");
            if(num == null){
                num = 0;
            }
            num++;
            application.setAttribute("num",num);
        %>
        您是当前第<%=num%>位访客。
    </body>
    </html>

getCookie.jsp

<%--
      Created by IntelliJ IDEA.
      User: southwind
      Date: 2019-07-09
      Time: 20:48
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>Title</title>
    </head>
    <body>
        <%
            Cookie[] cookies = request.getCookies();
            for (Cookie cookie:cookies){
                System.out.println(cookie.getMaxAge());
    //            System.out.println(cookie.getName()+"-"+cookie.getValue());
            }
        %>
    </body>
    </html>

index.jsp

<%--
      Created by IntelliJ IDEA.
      User: southwind
      Date: 2019-07-09
      Time: 20:13
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
      <head>
        <title>$Title$</title>
      </head>
      <body>
      欢迎回来！<%
        String username = (String) session.getAttribute("username");
      %>
      <%=username%>
      <a href="/logout.do">退出登录</a>
      </body>
    </html>

<%--
      Created by IntelliJ IDEA.
      User: southwind
      Date: 2019-07-09
      Time: 20:20
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>Title</title>
    </head>
    <body>
        <form action="/login.do" method="post">
            <input type="text" name="username"/>
            <input type="password" name="password"/>
            <input type="submit" value="登录"/>
        </form>
    </body>
    </html>

pageContext.jsp

<%--
      Created by IntelliJ IDEA.
      User: southwind
      Date: 2019-07-09
      Time: 21:39
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>Title</title>
    </head>
    <body>
        <%
            application.setAttribute("name","zhangsan");
            request.getRequestDispatcher("target.jsp").forward(request,response);
        %>
    </body>
    </html>

target.jsp

<%--
      Created by IntelliJ IDEA.
      User: southwind
      Date: 2019-07-09
      Time: 21:41
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>Title</title>
    </head>
    <body>
        <%
            String name = (String)application.getAttribute("name");
        %>
        <%=name%>
    </body>
    </html>

![1603260-20190713234617158-485391665.png][]

web.xml

<?xml version="1.0" encoding="UTF-8"?>
    <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">
    </web-app>

转载于:https://www.cnblogs.com/HiJackykun/p/11182708.html

[1603260-20190713234230994-1777442014.png]: /images/20211203/7e27e4666e034e679e83284fea0a5f84.png
[1603260-20190713234348099-703776325.png]: /images/20211203/29f3b0c68525464d8b0f2544a987c5cc.png
[1603260-20190713234617158-485391665.png]: /images/20211203/07a603095edd4c6bb729f96d5b262951.png