use <%, but just the < character.
A JSP tag is somewhat like an HTML tag. JSP tags can have a "start
tag", a "tag body" and an "end tag". The start and end tag both use
the tag name, enclosed in < and > characters.
The end starts with a / character after the < character.
The tag names have an embedded colon character : in them, the
part before the colon describes the type of the tag. For instance:
<some:tag>
body
</some:tag>
If the tag does not require a body, the start and end can be conveniently
merged together, as
<some:tag/>
Here by closing the start tag with a /> instead of > character, we are
ending the tag immediately, and without a body. (This syntax convention
is the the same as XML.)
Tags can be of two types: loaded from an external tag library, or predefined
tags. Predefined tags start with jsp: characters.
For instance, jsp:include is a predefined tag that is used to
include other pages.
We have already seen the include directive. jsp:include
is similar. But instead of loading the text of the included file
in the original file, it actually calls the included target at run-time
(the way a browser would call the included target. In practice, this
is actually a simulated request rather than a full round-trip between the
browser and the server). Following is an example of jsp:include
usage
<HTML>
<BODY>
Going to include hello.jsp...<BR>
<jsp:include page="hello.jsp"/>
</BODY>
</HTML>
Try it and see what you get. Now change the "jsp:include"
to "jsp:forward" and see what is the difference. These two
predefined tags are frequently very useful.
Exercise: Write a JSP to do either a forward or
an include, depending upon a boolean variable (hint: The
concepts of mixing HTML and scriptlets work with JSP tags also!)
No comments:
Post a Comment