Why we need inclusion in JSP pages?
Main purpose of using inclusion in JSP
pages is to reduce code redunancy and to promote reusability.
e.g
In many web applications, there are
some common elements you need to display in many pages. For example,
company logo, copy right information, and so on. Instead of
reproducing those common pieces in each of JSP pages, you can factor
those common code into other files and include them into JSP pages
using inclusion mechanism provided by JSP engine. The application's
maintainability (you just need to make changes in only one palce) and
reusability gets improved. e.g header and footer's
Types of Inclusion:
JSP engine supports two include
mechanisms: include directive and include action (or jsp:include).
Difference between static and
dynamic inclusion in jsp..
1. Static inclusion is Include
Directive and dynamic inclusion is Include Action.
2. The syntax for static include is
< %@ include file=”filename.jsp”
% > .
Where as the syntax for dynamic include
is
< jsp:include page=”filename.jsp”
/ >
3.The include directive allows a static
resource to be included in the page at translation time (JSP compile
time), and it is then parsed/translated along with the rest of the
JSP. The resulting page as one page therefore creating one
corresponding servlet. It’s something like a copy and pasting the
text from your include page right into your JSP.
The include action on the other hand is
a request time include, the included file is treated a separate
servlet which is executed at request time and its output "chained"
to the including servlet. The output produced by that (second) JSP is
included without being parsed or translated by the first JSP.
4. Static include cannot have a dynamic
filename. This is because the servlet container needs the files for
inclusion, at translation phase itself. But dynamic include can have
a dynamic filename. Here the file is getting included at runtime.
5. Static include cannot accept a
parameter. But dynamic include can accept a parameter..
e.g
< jsp:include page="file.jsp"
>
< jsp:param name="firstname"
value="Chaitanya" / >
< jsp:param name="middlename"
value="Pratap" / >
< jsp:param name="lastname"
value="Singh" / >
< /jsp:include >
6. Static includes are faster than
dynamic includes.
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