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JSP Custom Tag Attribute

Hi,

I've written myself a custom tag for a JSP, but i'm having a little trouble passing it an attribute.

The tag is supposed to be passing a parameter from a form that was submitted from a previous page, so i'm using:

<tag:hashingTag valueToHash="${param.answer}" />

This is what i've been using for the standard tags to pass variables, but for my tag it just passes in the String "${param.answer}", rather than the value that variable is holding.

Is there some setting i'm supposed to set to tell the tag this is a variable, not a String?

Cheers.

searlas

See:
http://java.sun.com/j2ee/1.4/docs/tutorial/doc/JSPIntro7.html

Depending on your application server, you may need to specify (at the top of your page)
<%@ page isELIgnored="false" %>

Additionally, the attributes on your custom tags must be set up in the tld file as <rtexprvalue>true</rtexprvalue>

searlas

Reading your post again, since you're successfully using "${...}" with the standard tags, then it would point to the problem being in your .tld file, and needing to declare <rtexprvalue>true</rtexprvalue> within the appropriate <attribute> elements.

playerone

ASKER

Thanks, but I'm already using <rtexprvalue>true</rtexprvalue>, here is this tag from my tld file:
      <tag>
            <name>hashingTag</name>
            <tagclass>tags.HashingTag</tagclass>
            <attribute>
                  <name>valueToHash</name>
                  <required>true</required>
                  <rtexprvalue>true</rtexprvalue>
            </attribute>
      </tag>

kennethxu

>> <tag:hashingTag valueToHash="${param.answer}" />
if you are not on a jsp2.0 server, you cannot use this as is.
let us know what server are you using?

playerone

ASKER

I'm currently using Tomcat 5 (although the page may be needed to run on Tomcat 4)

kennethxu

tomcat4 is jsp1.2, which doesn't support EL. you cannot use that in tomcat4.
if you have to do it for tomcat4, you'll need to parse the EL yourself. jakarta has a lib to do that.
let us know if your have further enquires.

playerone

ASKER

Ok, i've found the commons el lib on jakarta's website, but i can't find anything about how to use it!

I've downloaded the binary and put it in the lib folder for my app but can't see what to do next.

kennethxu

you'll need to change your tag lib to call the el lib, I'm trying to find you some code that I did before.

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kennethxu

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kennethxu

hold on, I just had a quick look at the el lib you found in jakarta, that one seems too requires jsp 2.0, I cannot be sure.

It is a very confused in el between jsp1.2/jstl1.0 and jsp2.0/jstl1.1. I would say, if your tag is going to be end up used in tomcat 4, you should probably stick developing on tomcat 4 as well. forget about the el lib, just use the one come with jstl1.0 (standard.jar and jstl.jar) my code above works with jstl1.0.

playerone

ASKER

yeah, thats done the trick!

my tags now running on Tomcat 4,

cheers!