Chapter 24: Creating JavaServer Pages

What a JSP contains

A JSP contains static template text that is written to the output stream. It also contains dynamic content that can take several forms:

Directives provide global information for the page, or include a file of text or code.
Scripting elements (declarations, scriptlets, and expressions) manipulate objects and perform computations.
Standard tags perform common actions such as instantiating or getting or setting the properties of a JavaBeans component, downloading a plug-in, or forwarding a request.
Custom tags perform additional actions defined in a custom tag library.

For more detailed information about using these content types, see “Application logic in JSPs”.

A simple example

This sample JSP contains a directive, a scripting element (in this case an expression), and a standard tag. The dynamic content is shown in bold:

<HTML>
<HEAD><TITLE>Simple JSP</TITLE>
</HEAD>
<BODY>
<P>This page uses three kinds of dynamic content: </P>
<UL><LI>A page directive that imports the java util package.
<%@ page import = "java.util.*" %>
<LI>An expression to get the current date using java.util.Date. Today's date is <%= new Date() %>.
<LI>An include tag to include data from another file without parsing the content. 
<jsp:include page="includedpage.txt" flush="true"/>
</UL>
</BODY>
</HTML>

The page referenced is a text file that contains one sentence and is in the same directory as the JSP file. The included page might also be another resource, such as a JSP file, and its location can be specified using a URI path.

You can call the JSP from an HTML page with a hypertext reference:

<html><body>
<p><a href="simplepage.jsp">Click here to send a request to the simple JSP.</p>
</body></html>

This HTML is returned to the browser:

<HTML>
<HEAD><TITLE>Simple JSP</TITLE>
</HEAD>
<BODY>
<P>This page uses three kinds of dynamic content: </P>
<UL><LI>A page directive that imports the java util package.
<LI>An expression to get the current date using java.util.Date. Today's date is Mon Feb 14 17:03:51 EST 2000.
<LI>An include tag to include data from another file without parsing the content.
In this case the included file is a static file containing this sentence.
</UL>
</BODY>
</HTML>

View this book as PDF