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JSP内置对象application、out、page、config，exception总结(五)

2017-11-22 18:38 776 查看

(一).application对象常用方法：

https://docs.oracle.com/javaee/7/api/javax/servlet/ServletContext.html

1.使用application获取指定页面的路径

<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
<center>

<h3>指定实际路径、相对路径、应用程序当前路径</h3>
</h>
<table border="1" bordercolor="black">
<tr>
<td>服务器名称和版本</td>
<td>index.jsp页面实际路径</td>
<td>index.jsp的URL</td>
<td>当前Web程序路径</td>

</tr>
<tr>
<td><%=application.getServerInfo()%></td>
<td><%=application.getRealPath("index.jsp") %></td>
<td><%=application.getResource("index.jsp") %></td>
<td><%=application.getContextPath()%></td>
</tr>
</table>
</center>
</body>
</html>

输出：

2.使用application保存网站访问人数，使得多个JSP，Servlet共享数据

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
Integer count =(Integer)
fbcc
application.getAttribute("count");
if(count==null){
count=1;
}else{
count++;
}
application.setAttribute("count",count);
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>网站计数器</title>
</head>
<body>
<center>
欢迎访问本网站，您是第<%=count %>位访问客户！
</center>
</body>
</html>

输出：

(二)out对象

1.out对象是Java.servlet.jsp.JspWriter类的实例

2.out对象常用方法：

https://tomcat.apache.org/tomcat-4.1-doc/servletapi/javax/servlet/jsp/JspWriter.html

3.实例演示

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>演示out对象</title>
</head>

<body>
<center>
<hr>
<h4>以下就是一个表格</h4>
<%
out.println("<table border='2'>");
out.println("<tr>");
out.println("<td width='60'>"+"姓名"+"</td>");
out.println("<td width='40'>"+"性别"+"</td>");
out.println("<td width='80'>"+"出生年月"+"</td>");
out.println("<td width='60'>"+"城市"+"</td>");
out.println("</tr>");
out.println("<tr>");
out.println("<td width='60'>"+"Smith"+"</td>");
out.println("<td width='60'>"+"Male"+"</td>");
out.println("<td width='60'>"+"1984.8"+"</td>");
out.println("<td width='60'>"+"NerYork"+"</td>");
out.println("</tr>");
out.println("</table>");
%>
</center>
</body>
</html>

输出：

(三)page对象

1.page对象就是Java.lang.Object对象

2.常用方法：https://docs.oracle.com/javase/7/docs/api/java/lang/Object.html

3.实例演示

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>演示page对象</title>
</head>

<body>
<center>
<%
int code = page.hashCode();
String str = page.toString();
out.println("page对象的hash码:"+code+"  </br>");
out.println("page对象的值:"+str);
%>
</center>
</body>
</html>

输出：

(四)config对象

1.config对象是javax.servlet.ServletConfig类的实例

2.常用方法：

https://docs.oracle.com/javaee/6/api/javax/servlet/ServletConfig.html

3.实例演示：

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>

<servlet>
<servlet-name>
jspconfigdemo
</servlet-name>
<jsp-file>/index.jsp</jsp-file>
<init-param>
<param-name>url</param-name>
<param-value>http://www.baidu.com</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>
jspconfigdemo
</servlet-name>
<url-pattern>/index.jsp</url-pattern>
</servlet-mapping>

</web-app>

----------
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>演示config对象</title>
</head>

<body>
<%
String url = config.getInitParameter("url");
String str = config.toString();
out.print("page对象的initParameter方法："+url+"</br>");
out.print("page对象的toString方法："+str);
%>
</body>
</html>

输出：

(五)exception对象的使用

说明：JPS异常处理机制，实际上就是Java异常处理机制

1.exception处理页面异常的方法

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8" errorPage="error.jsp" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>JSP脚本异常</title>
</head>
<body>
<%
int a=8;
int b=0;
int c=a/b;
%>
</body>
</html>

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"  isErrorPage="true"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>异常处理页面</title>
</head>
<body>
<hr>
异常类型：<%=exception.getClass() %><br/><br/>
异常信息： <%=exception.getMessage() %>
<hr>
</body>
</html>

做法是：
1.<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8" errorPage="error.jsp" %>

2.<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"  isErrorPage="true"%>

输出结果：

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