What Is a JSP Page?
A JSP page is a text document that contains two types of text: static data, which can be expressed in any text-based format (such as HTML, SVG, WML, and XML), and JSP elements, which construct dynamic content.
The recommended file extension for the source file of a JSP page is
.jsp
. The page can be composed of a top file that includes other files that contain either a complete JSP page or a fragment of a JSP page. The recommended extension for the source file of a fragment of a JSP page is.jspf
.The JSP elements in a JSP page can be expressed in two syntaxes--standard and XML--though any given file can use only one syntax. A JSP page in XML syntax is an XML document and can be manipulated by tools and APIs for XML documents. This chapter and Chapters 6 through 8 document only the standard syntax. The XML syntax is covered in Chapter 5.
Example
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.
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Figure 4-1 Localized Date Form
The source code for this example is in the
<
INSTALL
>/javaeetutorial5/examples/web/date/
directory. The JSP page,index.jsp
, used to create the form appears in a moment; 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 contain the following types of JSP constructs:
- A page directive (
<%@page ... %>
) sets the content type returned by the page.- Tag library directives (
<%@taglib ... %>
) import custom tag libraries.jsp:useBean
is a standard element that creates an object containing a collection of locales and initializes an identifier that points to that object.- JSP expression language expressions (
${ }
) retrieve the value of object properties. The values are used to set custom tag attribute values and create dynamic content.- Custom tags set a variable (
c:set
), iterate over a collection of locale names (c:forEach
), and conditionally insert HTML text into the response (c:if
,c:choose
,c:when
,c:otherwise
).jsp:setProperty
is another standard element that sets the value of an object property.- A function (
f:equals
) tests the equality of an attribute and the current item of a collection. (Note: A built-in==
operator is usually used to test equality.)Here is the JSP page:
<%@page contentType
="text/html; charset=UTF-8" %> <%@taglib
uri="http://java.sun.com/jsp/jstl/core
" prefix="c" %> <%@taglib
uri="/functions" prefix="f" %> <html> <head><title>Localized Dates</title></head> <body bgcolor="white"> <jsp:useBean
id="locales" scope="application" class="mypkg.MyLocales"/> <form name="localeForm" action="index.jsp" method="post"> <c:set
var="selectedLocaleString" value="${param.locale}
" /> <c:set
var="selectedFlag" value="${!empty selectedLocaleString}
" /> <b>Locale:</b> <select name=locale> <c:forEach
var="localeString" items="${locales.localeNames}
" > <c:choose
> <c:when
test="${selectedFlag}
"> <c:choose
> <c:when
test="${f:equals(selectedLocaleString, localeString)}
" > <option selected>${localeString}
</option> </c:when> <c:otherwise> <option>${localeString}
</option> </c:otherwise> </c:choose> </c:when> <c:otherwise
> <option>${localeString}
</option> </c:otherwise> </c:choose> </c:forEach> </select> <input type="submit" name="Submit" value="Get Date"> </form> <c:if
test="${selectedFlag}" > <jsp:setProperty
name="locales" property="selectedLocaleString" value="${selectedLocaleString}
" /> <jsp:useBean
id="date" class="mypkg.MyDate"/> <jsp:setProperty
name="date" property="locale" value="${locales.selectedLocale}
"/> <b>Date: </b>${date.date}
</c:if> </body> </html>To deploy the
date
application with NetBeans 5.5, follow these steps:
- Start the Application Server.
- In NetBeans 5.5, select File
Open Project.
- In the Open Project dialog, navigate to:
<INSTALL>/javaeetutorial5/examples/web/
- Select the
date
folder.- Select the Open as Main Project checkbox.
- Click Open Project Folder.
- In the Projects tab, right-click the
date
project, and select Deploy Project.To deploy the
date
application with the Ant tool, follow these steps:To run the example, do the following:
Some of the characters might not display properly if you don't have the appropriate language files installed on your machine. Consult the user guide or online help for your operating system to determine how you can install these language files.