jsp提供了9个内置对象,该对象会自动进行实例化操作

4种属性范围

page 只在一个保存属性,跳转无效
request 一次请求保存属性,跳转依旧有效
session 同一会话有效
application 整个服务器上保存,所有用户都可使用

page属性

一个属性设置在本页上,跳转后无法获得

<%@ page import="java.util.Date" %><%--
  Created by IntelliJ IDEA.
  User: ming
  Date: 19-3-10
  Time: 下午1:02
  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>
<%
    // 设置page属性
    pageContext.setAttribute("name", "ming");
    pageContext.setAttribute("birtday", new Date());
%>
<%
    // 重page中取出属性
    String username = (String)pageContext.getAttribute("name");
    Date userbirthday = (Date)pageContext.getAttribute("birtday");
%>
姓名 <%=username%>
生日 <%=userbirthday%>
</body>
</html>

request 属性

服务器跳转后,属性会被继续保存
浏览器的URL地址会发生改变

<%@ page import="java.util.Date" %><%--
  Created by IntelliJ IDEA.
  User: ming
  Date: 19-3-10
  Time: 下午1:02
  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>
<%
    request.setAttribute("name", "ming");
    request.setAttribute("birthday", new Date());
%>
<jsp:forward page="request_scope_02.jsp"/>
</body>
</html>

<%@ page import="java.util.*" %><%--
  Created by IntelliJ IDEA.
  User: ming
  Date: 19-3-10
  Time: 下午1:29
  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)request.getAttribute("name")%>
<%=(Date)request.getAttribute("birthday")%>
</body>
</html>

session属性

当一个属性设置以后,任何一个与设置页面相关的页面都可以取得
即,session,session属于服务器端保存.

cokice 属于客户端保存

<%--
  Created by IntelliJ IDEA.
  User: ming
  Date: 19-3-10
  Time: 下午3:07
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page import="java.util.*" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<%
    // 设置session属性范围
    session.setAttribute("name", "ming");
    session.setAttribute("birthday", new Date());
%>
<!-- 超链接跳转 -->
<a href="session_scope_02.jsp">超级链接跳转</a>
</body>
</html>

<%--
  Created by IntelliJ IDEA.
  User: ming
  Date: 19-3-10
  Time: 下午3:07
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page import="java.util.*" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<%
    // 取出session属性
    String username = (String)session.getAttribute("name");
    Date userbirthday = (Date)session.getAttribute("birthday");
%>
<%=username%>
<%=userbirthday%>
</body>
</html>

application

此为公共参数
此属性保存在服务器上

<%@ page import="java.util.Date" %><%--
  Created by IntelliJ IDEA.
  User: ming
  Date: 19-3-10
  Time: 下午10:17
  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", "ming");
    application.setAttribute("birthday", new Date());
%>
<!-- 超级链接跳转 -->
<a href="./application_scope_02.jsp">超级链接获得属性</a>
</body>
</html>

<%@ page import="java.util.Date" %><%--
  Created by IntelliJ IDEA.
  User: ming
  Date: 19-3-10
  Time: 下午10:20
  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>
<%
    // application中获得属性
    String username = (String)application.getAttribute("name");
    Date userbirthday = (Date)application.getAttribute("birthday");
%>
<%=username%>
<%=userbirthday%>
</body>
</html>

request对象

接收客户端发送的请求,请求的参数,头部信息.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <form action="request_demo01.jsp" method="post">
        <input type="text" name="info">
        <input type="submit" value="submit">
    </form>
</body>
</html>
<%--
  Created by IntelliJ IDEA.
  User: ming
  Date: 19-3-10
  Time: 下午11:54
  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>
<%
    // 接收参数
    String content = request.getParameter("info");
%>
<%=content%>
</body>
</html>

接收全部请求参数

用getParameterNames

显示全部头信息

使用getHeaderNames()

角色验证

额...依旧没啥东东
学过

response

定时跳转

定时跳转属于客户端跳转

额..依旧没啥
在response中调用addCookie
需要注意的是会返回一个jsessionid

session

当服务器端使用session的时候,可以保存在redis中
会有一个不重复的编号,即session id

cookie中保存的jsessionid为同样道理

登录 注销

实现思路,设置session范围的属性,需要验证的页面进行判断session
即,保存用户的信息,使用session进行保存

<%--
  Created by IntelliJ IDEA.
  User: ming
  Date: 19-3-11
  Time: 下午9:17
  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.jsp" method="post">
        用户名
        <input type="text" name="uname"/>
        密码
        <input type="password" name="upass"/>
        <input type="submit" value="登录">
    </form>
<%
    // 用户名 密码
    // 获得name
    String name = request.getParameter("uname");
    // 获得password
    String password = request.getParameter("upass");
    // 进行用户名密码比对
    if(!(name==null||"".equals(name)
        || password == null || "".equals(password))
    ){
        if("admin".equals(name) && "admin".equals(password)){
            // 跳转
            response.setHeader("refresh", "2;URL=welcome.jsp");
            // 设置session
            session.setAttribute("userid", name);
        %>
            <h3>用户登录成功,两秒后将会跳转到欢迎页!</h3>
            <h3>如果没有跳转,点击<a href="./welcome.jsp">这里</a></h3>
        <%
        }else{
            %>
                <h3>用户名密码错误</h3>
            <%
        }
    }
%>
</body>
</html>

<%--
  Created by IntelliJ IDEA.
  User: ming
  Date: 19-3-11
  Time: 下午10:06
  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>
<%
    // 设置两秒跳转
    response.setHeader("refresh", "2;URL=login.jsp");
    // 清除session
    session.invalidate();
%>
<h3>成功退出本系统,两秒跳转回首页</h3>
<h3>如果没有跳转,访问<a href="login.jsp">点我</a> </h3>
</body>
</html>

<%--
  Created by IntelliJ IDEA.
  User: ming
  Date: 19-3-11
  Time: 下午9:59
  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>
<%
    // 判断此用户的session是否设置过
    if(session.getAttribute("userid")!=null){
        %>
            <h3>欢迎<%=session.getAttribute("userid")%></h3>
            <h3>注销登录<a href="./logout.jsp">点我</a></h3>
        <%
    }else{
        %>
            <h3>非法访问</h3>
        <%
    }
%>
</body>
</html>

判断新用户

使用isnew的方式,
原理,在第一次访问的时候,给客户端设置cokkie,然后再次访问的时候,会带上cokkie中的jsessionid,用来判断是否为新用户

用户操作时间

使用getCreationTime获取第一个session创建的session时间,和最后一次操作的时间,用来判断秒数

application对象

用来获取serlet对象上下文 ServletContext表示整个容器的操作
使用表单输入要保存的文件名称和内容,直接在web项目的根目录的note文件夹中保存文件

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <form action="./input_content.jsp" method="post">
        输入文件名称 <input type="text" name="filename"/><br/>
        输入文件内容 <textarea name="filecontent" cols="30" rows="3">
    </textarea>
        <input type="submit" value="保存"/>
        <input type="reset" value="重置"/>
    </form>
</body>
</html>
<%@ page import="java.io.File" %>
<%@ page import="java.io.PrintStream" %>
<%@ page import="java.io.FileOutputStream" %>
<%@ page import="java.util.Scanner" %>
<%@ page import="java.io.FileInputStream" %><%--
  Created by IntelliJ IDEA.
  User: ming
  Date: 19-3-11
  Time: 下午10:46
  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>
<%
    // 接收保存的文件名称
    String name = request.getParameter("filename");
    // 接收文件内容
    String content = request.getParameter("filecontent");
    // 获得文件名称
    String fileName = this.getServletContext().getRealPath("/") + "note" + File.separator + name;
    // 获得文件对象
    File file = new File(fileName);
    // 用于判断父文件夹是否存在
    if(!file.getParentFile().exists()){
        // 创建文件夹
        file.getParentFile().mkdir();
    }
    // 定义打印流对象
    PrintStream printStream = null;
    // 创建一个到文件的输入流
    printStream = new PrintStream(new FileOutputStream(file));
    // 往流中输入内容
    printStream.println(content);
    // 关闭流
    printStream.close();
%>
<%
    // 通过Scanner获取流的输入
    Scanner scanner = new Scanner(new FileInputStream(file));
    // 设置读取分隔符
    scanner.useDelimiter("\n");
    // 新建缓冲区
    StringBuffer stringBuffer = new StringBuffer();
    // 读取内容,保存进入缓冲区
    while(scanner.hasNext()){
        stringBuffer.append(scanner.next()).append("<br>");
    }
    // 关闭
    scanner.close();
%>
<%=stringBuffer%>
</body>
</html>