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
操作cookie
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>JSP 内置对象(一)
原文地址：https://www.cnblogs.com/melovemingming/p/10538777.html