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12.2 Including Files at Request Time

271

Although the included files cannot contain JSP, they can be the result of

resources that use JSP to create the output. That is, the URL that refers to

the included resource is interpreted in the normal manner by the server and

thus can be a servlet or JSP page. This is precisely the behavior of the

include

 method of the 

RequestDispatcher

 class, which is what servlets

use if they want to do this type of file inclusion. See Section 15.3 (Including

Static or Dynamic Content) for details.

The 

jsp:include

 element has two required attributes, as shown in the

sample below: 

page

 (a relative URL referencing the file to be included) and

flush

 (which must have the value 

true

).

Although you typically include HTML or plain text documents, there is no

requirement that the included files have any particular file extension. How 

ever, the Java Web Server 2.0 has a bug that causes it to terminate page pro 

cessing when it tries to include a file that does not have a 

.html

 or 

.htm

extension (e.g., 

somefile.txt

). Tomcat, the JSWDK, and most commercial

servers have no such restrictions.

Core Warning

Due to a bug, you must use 

.html

 or 

.htm

 extensions for included files 

used with the Java Web Server.

As an example, consider the simple news summary page shown in Listing

12.3. Page developers can change the news items in the files 

Item1.html

through 

Item4.html

 (Listings 12.4 through 12.7) without having to update

the main news page. Figure 12 2 shows the result.

Listing 12.3 WhatsNew.jsp