Java/JSP/Page Context
Содержание
Application Object
<source lang="java">
//File Name: application_page1.jsp <%
String theSharedObject = "JSP is cool";
application.setAttribute("message", theSharedObject);
%> <HTML>
<HEAD> <TITLE>Application Object - Page 1</TITLE> </HEAD> <BODY>This page sets data that can be retrieved by other pages in the application.
Click to see this in action. </BODY> </HTML> //File Name:application_page2.jsp <% // getAttribute() returns a java.lang.Object, so need to cast String theSharedObject = (String) application.getAttribute("message"); %> <HTML> <HEAD> <TITLE>Application Object - Page 2</TITLE> </HEAD> <BODY> This page retrieves the message that was stored in the application object by another page. <P> The message is <%= theSharedObject %> </BODY> </HTML> </source>
JSP page scope
<source lang="java">
<jsp:useBean id="myBookBean" class="com.jexp.Book"
scope="page" />
<html>
<head> <title>page scope</title> </head> <body> This page declares a page-scoped Book. </body>
</html>
</source>
Page directive attributes
<source lang="java">
<%@ page autoFlush="true"
buffer="16kb"
contentType="text/html"
errorPage="myErrorPage.jsp"
extends="org.apache.jasper.runtime.HttpJspBase"
import="java.sql.*"
info="This page has a set of page directive attributes"
language="java"
pageEncoding="UTF-8"
session="false"
%> <HTML>
<HEAD><TITLE>Page directive attributes</TITLE></HEAD> <BODY> The JSP page used to generate this content defined values for all of the page directive"s attributes. </BODY>
</HTML>
</source>
Set JSP PageContext attributes
<source lang="java">
<%@ taglib prefix="c" uri="http://java.sun.ru/jstl/core" %> <%
synchronized (pageContext) {
Class thisClass = getClass();
// session.setAttribute("thisClass", thisClass);
pageContext.setAttribute("thisClass", thisClass, PageContext.PAGE_SCOPE);
System.out.println("Stored reference");
Class theClass = (Class) pageContext.getAttribute("thisClass", PageContext.PAGE_SCOPE);
System.out.println("The retrieved reference is " + theClass);
}
%> <html>
<body>
The class that instantiated this JSP is <c:out value="${pageScope.thisClass.name}" />.
</body>
</html>
</source>
Set page parameters
<source lang="java">
<html>
<head> <title>Set page parameters</title> </head> <body> This page allows you to enter information that is sent as request parameters to another page. The next page lists them. <P /> <form action="listPageParameters.jsp" method="get">
| Enter an adjective: | <input type="text" name="adjective" /> |
| Enter a noun: | <input type="text" name="noun" /> |
| Enter a color: | <input type="text" name="color" /> |
<input type="submit" value="Send parameters" /> </form> </body>
</html> //listPageParameters.jsp
<%@ taglib prefix="c" uri="http://java.sun.ru/jstl/core" %> <html>
<head> <title>List page parameters</title> </head> <body> You entered the following parameters:
-
<%-- "param" is an implicit object. It is a Map that maps a "key"
(the parameter name) to a "value" --%>
<c:forEach var="pageParameter" items="${param}">
- <c:out value="${pageParameter.key}" /> = <c:out value="${pageParameter.value}" /> </c:forEach>
</body>
</html>
</source>
