You can use either a JSP directive or a standard action to include page fragments a JSP page. This is a useful technique when parts of all pages in an application are the same, such as headers, footers, and navigation bars.
include directive reads the content
of the specified page in the
translation phase (when the JSP page is converted into a servlet) and
merges it with the original page:
<%@ include file="header.htmlf" %>
file attribute is a relative path. If it
starts with a slash, it’s a context-relative path,
interpreted relative to the context path assigned for the
application. If it doesn’t start with a slash,
it’s a page-relative path, interpreted relative to
the path for the page that includes the file.
The included file can contain either only static content (such as
HTML) or it can be a regular JSP page. Its content is merged with the
page that includes it, and the resulting page is converted into a
servlet as described in Chapter 3. This means that
the main page and all included pages share all page scope data.
Scripting variables declared in JSP declarations, scriptlets, or
actions, such as
<jsp:useBean> or custom
actions that introduce scripting variables, are also shared.
Consequently, if the main page declares a variable, and the same name
is used for another variable in an included page, it results in a
translation phase error, because the combined page
can’t be compiled.
One common use for the
include directive is to include ...