What Is a JSP Page?

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What Is a JSP Page?

A JSP page is a text-based document that contains two types of text: static template data, which can be expressed in any text-based format, such as HTML, SVG, WML, and XML; and JSP elements, which construct dynamic content. A syntax card and reference for the JSP elements are available at
http://java.sun.com/products/jsp/technical.html#syntax
The Web page in Figure 4-1 is a form that allows you to select a locale and displays the date in a manner appropriate to the locale.

[画像:Localized Date Form]

Figure 4-1 Localized Date Form

The source code for this example is in the docs/tutorial/examples/web/date directory created when you unzip the tutorial bundle. The JSP page index.jsp used to create the form appears below; it is a typical mixture of static HTML markup and JSP elements. If you have developed Web pages, you are probably familiar with the HTML document structure statements (<head>, <body>, and so on) and the HTML statements that create a form <form> and a menu <select>. The lines in bold in the example code contains the following types of JSP constructs:
Directives (<%@page ... %>) import classes in the java.util package and the MyLocales class, and set the content type returned by the page.

The jsp:useBean element creates an object containing a collection of locales and initializes a variable that points to that object.

Scriptlets (<% ... %> ) retrieve the value of the locale request parameter, iterate over a collection of locale names, and conditionally insert HTML text into the output.

Expressions (<%= ... %>) insert the value of the locale name into the response.

The jsp:include element sends a request to another page (date.jsp) and includes the response in the response from the calling page.
<%@ page import="java.util.*,MyLocales" %>
<%@ page contentType="text/html; charset=ISO-8859-5" %>
<html>
<head><title>Localized Dates</title></head>
<body bgcolor="white">
<jsp:useBean id="locales" scope="application" 
 class="MyLocales"/>
<form name="localeForm" action="index.jsp" method="post">
<b>Locale:</b>
<select name=locale>
<% 
 String selectedLocale = request.getParameter("locale");
 Iterator i = locales.getLocaleNames().iterator();
 while (i.hasNext()) {
  String locale = (String)i.next();
  if (selectedLocale != null &&
   selectedLocale.equals(locale)) {
%>
   <option selected><%=locale%></option>
<% 
  } else { 
%>
   <option><%=locale%></option>
<%
  } 
 }
%>
</select>
<input type="submit" name="Submit" value="Get Date">
</form>
<jsp:include page="date.jsp"/>
</body>
</html>
The source for the Duke's Bookstore application is located in the <INSTALL>/j2eetutorial/examples/web/date directory.

To build, deploy, and execute this JSP page:

In the IDE, mount the filesystem
<INSTALL>/j2eetutorial/examples/web/date.

Expand the date node.

Right-click the WEB-INF directory and choose Deploy.

Right-click the WEB-INF directory and choose Execute.

You will see a combo box whose entries are locales. Select a locale and click Get Date. You will see the date expressed in a manner appropriate for that locale.

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All of the material in The J2EE Tutorial for the Sun ONE Platform is copyright-protected and may not be published in other works without express written permission from Sun Microsystems.