jsp提供了9個內置對象,該對象會自動進行實例化操作
4種屬性範圍
page 只在一個保存屬性,跳轉無效
request 一次請求保存屬性,跳轉依舊有效
session 同一會話有效
application 整個服務器上保存,所有用戶都可使用
page屬性
一個屬性設置在本頁上,跳轉後無法獲得
<%@ 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>
<%
// 設置page屬性
pageContext.setAttribute("name", "ming");
pageContext.setAttribute("birtday", new Date());
%>
<%
// 重page中取出屬性
String username = (String)pageContext.getAttribute("name");
Date userbirthday = (Date)pageContext.getAttribute("birtday");
%>
姓名 <%=username%>
生日 <%=userbirthday%>
</body>
</html>
request 屬性
服務器跳轉後,屬性會被繼續保存
瀏覽器的URL地址會發生改變
<%@ 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屬性
當一個屬性設置以後,任何一個與設置頁面相關的頁面都可以取得
即,session,session屬於服務器端保存.
cokice 屬於客戶端保存
<%--
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>
<%
// 設置session屬性範圍
session.setAttribute("name", "ming");
session.setAttribute("birthday", new Date());
%>
<!-- 超鏈接跳轉 -->
<a href="session_scope_02.jsp">超級鏈接跳轉</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屬性
String username = (String)session.getAttribute("name");
Date userbirthday = (Date)session.getAttribute("birthday");
%>
<%=username%>
<%=userbirthday%>
</body>
</html>
application
此爲公共參數
此屬性保存在服務器上
<%@ 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());
%>
<!-- 超級鏈接跳轉 -->
<a href="./application_scope_02.jsp">超級鏈接獲得屬性</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中獲得屬性
String username = (String)application.getAttribute("name");
Date userbirthday = (Date)application.getAttribute("birthday");
%>
<%=username%>
<%=userbirthday%>
</body>
</html>
request對象
接收客戶端發送的請求,請求的參數,頭部信息.
<!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>
<%
// 接收參數
String content = request.getParameter("info");
%>
<%=content%>
</body>
</html>
接收全部請求參數
用getParameterNames
顯示全部頭信息
使用getHeaderNames()
角色驗證
額...依舊沒啥東東
學過
response
定時跳轉
定時跳轉屬於客戶端跳轉
操作cookie
額..依舊沒啥
在response中調用addCookie
需要注意的是會返回一個jsessionid
session
當服務器端使用session的時候,可以保存在redis中
會有一個不重複的編號,即session id
cookie中保存的jsessionid爲同樣道理
登錄 註銷
實現思路,設置session範圍的屬性,需要驗證的頁面進行判斷session
即,保存用戶的信息,使用session進行保存
<%--
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">
用戶名
<input type="text" name="uname"/>
密碼
<input type="password" name="upass"/>
<input type="submit" value="登錄">
</form>
<%
// 用戶名 密碼
// 獲得name
String name = request.getParameter("uname");
// 獲得password
String password = request.getParameter("upass");
// 進行用戶名密碼比對
if(!(name==null||"".equals(name)
|| password == null || "".equals(password))
){
if("admin".equals(name) && "admin".equals(password)){
// 跳轉
response.setHeader("refresh", "2;URL=welcome.jsp");
// 設置session
session.setAttribute("userid", name);
%>
<h3>用戶登錄成功,兩秒後將會跳轉到歡迎頁!</h3>
<h3>如果沒有跳轉,點擊<a href="./welcome.jsp">這裏</a></h3>
<%
}else{
%>
<h3>用戶名密碼錯誤</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>
<%
// 設置兩秒跳轉
response.setHeader("refresh", "2;URL=login.jsp");
// 清除session
session.invalidate();
%>
<h3>成功退出本系統,兩秒跳轉回首頁</h3>
<h3>如果沒有跳轉,訪問<a href="login.jsp">點我</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>
<%
// 判斷此用戶的session是否設置過
if(session.getAttribute("userid")!=null){
%>
<h3>歡迎<%=session.getAttribute("userid")%></h3>
<h3>註銷登錄<a href="./logout.jsp">點我</a></h3>
<%
}else{
%>
<h3>非法訪問</h3>
<%
}
%>
</body>
</html>
判斷新用戶
使用isnew的方式,
原理,在第一次訪問的時候,給客戶端設置cokkie,然後再次訪問的時候,會帶上cokkie中的jsessionid,用來判斷是否爲新用戶
用戶操作時間
使用getCreationTime獲取第一個session創建的session時間,和最後一次操作的時間,用來判斷秒數
application對象
用來獲取serlet對象上下文 ServletContext表示整個容器的操作
使用表單輸入要保存的文件名稱和內容,直接在web項目的根目錄的note文件夾中保存文件
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<form action="./input_content.jsp" method="post">
輸入文件名稱 <input type="text" name="filename"/><br/>
輸入文件內容 <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>
<%
// 接收保存的文件名稱
String name = request.getParameter("filename");
// 接收文件內容
String content = request.getParameter("filecontent");
// 獲得文件名稱
String fileName = this.getServletContext().getRealPath("/") + "note" + File.separator + name;
// 獲得文件對象
File file = new File(fileName);
// 用於判斷父文件夾是否存在
if(!file.getParentFile().exists()){
// 創建文件夾
file.getParentFile().mkdir();
}
// 定義打印流對象
PrintStream printStream = null;
// 創建一個到文件的輸入流
printStream = new PrintStream(new FileOutputStream(file));
// 往流中輸入內容
printStream.println(content);
// 關閉流
printStream.close();
%>
<%
// 通過Scanner獲取流的輸入
Scanner scanner = new Scanner(new FileInputStream(file));
// 設置讀取分隔符
scanner.useDelimiter("\n");
// 新建緩衝區
StringBuffer stringBuffer = new StringBuffer();
// 讀取內容,保存進入緩衝區
while(scanner.hasNext()){
stringBuffer.append(scanner.next()).append("<br>");
}
// 關閉
scanner.close();
%>
<%=stringBuffer%>
</body>
</html>