6.7 其他内置对象
6.7.1 获取会话范围的pageContext对象
| 方法 | 说明 |
|---|---|
forward(String arg0) |
把页面转发到另一个页面 |
getAttribute(String arg0) |
获取参数值 |
getAttributeNamesInScope(int arg0) |
获取某范围的参数名称的集合，返回Enuneration |
getException() |
返回exception对象 |
getRequest() |
返回request对象 |
getResponse() |
返回response |
getSession() |
返回session对象 |
getOut() |
返回out对象 |
setAttribute(String arg0, String arg1) |
设置属性值 |
removeAttribute(String arg0,int arg1) |
删除指定范围内的指定属性 |
6.7.2 读取web.xml配置信息的config对象
| 方法 | 说明 |
|---|---|
getServletName() |
获取servlet服务器名 |
getServletContext() |
获取servlet上下文 |
getInitParameterNames() |
获取服务器所有初始参数名称，返回值为java.util.Enumeration对象 |
getInitParameter(String arg0) |
获取服务器中name参数的初始值 |
6.7.3 应答或请求的page对象
这个对象就是页面实例的引用。它可以被看做是整个JSP页面的代表。
page 对象就是this对象的同义词。
| 方法 | 说明 |
|---|---|
getClass() |
返回当前Object的类 |
hashCode() |
返回该Object的哈希代码 |
toString() |
转换字符串 |
equals(Object arg0) |
比较该对象和指定对象是否相等 |
6.7.4 获取异常信息的exception对象
exception 对象包装了从先前页面中抛出的异常信息。它通常被用来产生对出错条件的适当响应。
6.8实践练习
1.添加留言和显示留言
微信截图_20190817104652.png
微信截图_20190817104709.png
- message_book.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'message_book.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<form action="message_show.jsp" method="post" >
<table width="500" height="300" align="center" border="1" bordercolor="#66B3FF">
<tr>
<td height="30" align="center">留言簿</td>
</tr>
<tr>
<td height="200" align="center">
<textarea rows="10" cols="60" name="message"></textarea>
</td>
</tr>
<tr>
<td height="30" align="center">
<input value="提交" type="submit" />
</td>
</tr>
</table>
</form>
</body>
</html>
- message_show.jsp
<%@page import="java.net.URLEncoder"%>
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<%String messageStr= request.getParameter("message") ;
messageStr=new String(messageStr.getBytes("ISO-8859-1"),"UTF-8");
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'message_show.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<form action="message_book.jsp" method="post" >
<table width="500" height="300" align="center" border="1" bordercolor="#66B3FF">
<tr>
<td height="200" align="center">
<%=messageStr %>
</td>
</tr>
<tr>
<td height="30" align="center">
<input value="返回" type="submit" />
</td>
</tr>
</table>
</form>
</body>
</html>
2.账号密码登录，错误将页面重定向到错误页面
- signin.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>登录页面</title>
</head>
<body>
<form action="signin_check.jsp" method="post">
账号：<input name="username" type="text"/><br>
密码：<input name="password" type="password"/><br>
<input name="登录" type="submit"/><br>
</form>
</body>
</html>
- signin_check.jsp
<%@page import="javax.xml.soap.Text"%>
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'signin_success.jsp' starting page</title>
</head>
<body>
<%
String username= request.getParameter("username");
String password= request.getParameter("password");
%>
<%
if(username.equals("admin")&&password.equals("123456")){
out.print("账号、密码正确");
}else{
response.sendRedirect("signin_error.jsp");
}
%>
</body>
</html>
- signin_error.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'signin_error.jsp' starting page</title>
</head>
<body>
登录错误. <br>
<%
%>
</body>
</html>
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