JSP 内置对象(一)

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jsessionidsession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 idcookie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>