CODEWITHSUNDEEP
javajsp
ripper234
ripper234

Reputation: 230028

How can I reuse code in JSP?

For example, a user will be rendered throughout my application as

<div class="user">
  <p class="username">${user.name}</p>
  <p class="karma">${user.karma}</p>
  <img src="/users/${user.id}"/>
</div>

How can I reuse this code block?

Note - my code is running within a tag, so I can't use tags for this (or any JSP) otherwise I get a Scripting elements are disallowed here error.

Edit

I'm trying to use a tag file, but getting PropertyNotFoundException.

This is my tag file called 'user.tag':

<%@tag description="User" pageEncoding="UTF-8" %>

<a href="../user/showUser.do?userId=${user.id}">
    <p>${user.name}</p>
    <img class='avatar' src='${user.avatarUrl}' alt=""/>
</a>

And usage inside a jsp:

Where job.poster is a java bean with id, name, and avatarUrl properties. If I add 

<%@attribute name="user" %>

to the tag file, then I get an exception 

Property 'id' not found on type java.lang.String

Upvotes: 4

Views: 7506

Answers (5)

JohnnyMarnell
JohnnyMarnell

Reputation: 51

I feel sometimes creating a .tag file is overkill (especially if it's only for one page), and I've wanted what you describe for years, so I wrote my own, simple solution. See here: https://stackoverflow.com/a/25575120/1607642

Upvotes: 0

McDowell
McDowell

Reputation: 108879

You should be able to use tag files within tag files; this works for me in a JSP 2.2 container:

<%-- mytag.tag --%>
<%@tag description="demo code" pageEncoding="UTF-8"%>
<%@taglib prefix="cust" tagdir="/WEB-INF/tags" %>
<%@attribute name="message"%>
<cust:mytag2 message="${message}" /><%-- uses mytag2.tag --%>

If that fails, you can use the include directive: <%@include file="/WEB-INF/jspf/fragment.jspf" %>

Note that the spec says about tags:

Directive Available? Interpretation/Restrictions
======================================================================
page      no         A tag file is not a page. The tag directive must
                     be used instead. If this directive is used in a
                     tag file, a translation error must result.

So, fragment.jspf must not have a any elements that are not supported in tags, including a page directive.

Upvotes: 2

fforw
fforw

Reputation: 5491

Since JSP 2.0, there is yet another kind of tags: Tag files. Tag files are JSP custom tags written as a JSP template itself, which seems to be what you want.

http://fforw.de/post/creating-jsp-layouts-with-page-tags/ shows how to use such a tag file as general layout solution. Using them as component should be even easier.

Upvotes: 7

Ramesh PVK
Ramesh PVK

Reputation: 15446

Why don't you use a custom tag or jsp functions.

Thanks,

Upvotes: -1

planetjones
planetjones

Reputation: 12633

For the example you have given it sounds like some templating framework is needed, to display the user badge on each screen. At its simplest level this may just be a jsp:include which always includes your "UserBadge.jsp".

If you are running on a web framework e.g. JSF you may use Facelet templates or write a custom component for this. So the answer depends on what framework you have. Breaking it down to just JSP and JSTL - the included JSP or a javax.servlet.jsp.tagext.Tag would certainly reduce the duplication.

Always be careful to follow the DRY Principle... Don't Repeat Yourself!

Upvotes: 1

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