RE: Options1: Just Say No (was Re: cvs commit: jakarta-struts/web /documentation tags.html)

[Scott Ganyo <sc...@eTapestry.com>]

Hehe.  Maybe the 1.1 version of OptionsTag should be called
OptionsToSupportThatLegacyStuffTag. ;)

Scott

> -----Original Message-----
> From: Craig R. McClanahan [mailto:Craig.McClanahan@eng.sun.com]
> Sent: Monday, July 17, 2000 12:32 PM
> To: struts-user@jakarta.apache.org
> Cc: struts-dev@jakarta.apache.org
> Subject: Re: Options1: Just Say No (was Re: cvs commit:
> jakarta-struts/web/documentation tags.html)
> 
> 
> David Geary wrote:
> 
> > >   <struts:options1> is a version of <struts:options> that 
> is compatible with
> > >   JDK 1.1, and can enumerate over an array, a Dictionary 
> (including a
> > >   Hashtable), an Enumeration, or a Vector.
> >
> > I'm sorry, but this is horrible. Why? For the same reason 
> that struts tags are not named tag1, tag2, tag3, ...
> >
> > We have EnumerateTag, which is for 1.1, and IterateTag, 
> which is for 1.2. That's bad enough, but at least it's 
> apparent which tag
> > applies to what version of the JDK; that is, if you know 
> that Iterator was added in 1.2, and you understand that there 
> is no difference
> > between EnumerateTag and IterateTag except for their 
> private iteration algorithm, which really should be nobody's 
> business but their
> > own.
> >
> > Now we have OptionsTag and Options1Tag, which share all of 
> the drawbacks that EnumerateTag and IterateTag exhibit, but 
> in addition:
> > Which tag is for 1.1 and which is for 1.2?
> >
> > Please don't force me to select which JDK version is 
> supported by struts tags by using different tags with obscure 
> names. All struts
> > tags should work with both 1.1 and 1.2 collections. 
> Developers shouldn't even have to think about it.
> >
> > The worst part of all this is that a simple implementation 
> of the Adapter design pattern can eliminate all of the 
> duplicate classes,
> > leaving us with just IterateTag and OptionsTag.
> >
> 
> Having a single version of each tag is the ideal scenario, and is used
> in *most* of the Struts tags.  The only cases where there are two
> versions is when a tag wants to use the Java2 collections classes.
> 
> So, let's say I want to have just one version of the 
> "options" tag (for
> example, that supports collections if they are there, and doesn't
> if they are not there (do you ***really*** want to find out about this
> kind of problem at runtime instead of compile time?  OK, let's
> assume you do for the sake of this discussion.)  Now, how do we code
> such a tag.
> 
> The simple approach would be to try using the Java2 version 
> of the tag,
> which includes (among other things), "import java.util.Map".  How
> likely is that to compile in a JDK 1.1 environment?  You've 
> got it -- no
> way.
> 
> Well, let's just restrict things so that you have to compile Struts
> under Java2, and then try to use that tag under JDK 1.1.  What happens
> now?  The tag won't load, because you will get a NoClassDefFoundError
> exception when the JDK 1.1 JVM tries to load classes and interfaces
> that this class depends on, and does not find them.
> 
> You can write an adapter class, or you can use reflection (and pay the
> performance price), but the bottom line is this -- Struts users
> should view JDK 1.1 support as *temporary*, not permanent.  Therefore,
> all of the "1" versions of the classes will eventually go away, and
> I do not feel motivated to spend anything more than minimal effort to
> support JDK 1.1 users with compatible tags in the mean time.  This is
> the motivation for the "1" naming convention -- those tags are always
> the JDK 1.1 equivalents.  By that token, "enumerate" should really
> have been "iterate1" but I wasn't thinking far enough ahead 
> at the time.
> 
> Why the emphasis on "temporary"?  Because, as I got permission to
> announce on the TOMCAT-DEV mailing list, the next version of 
> the Servlet
> API (version 2.3), is currently planned to include a 
> dependency on Java2
> (JDK 1.2 or later).  Given that this is the future, and that Java2
> platforms are becoming available on all reasonable platforms, my
> interest in JDK 1.1 support is to give people transitional 
> tags that are
> functionally equivalent.  If you're in a Java2 world already, just
> ignore the JDK 1.1 tags and they will go away.
> 
> For the record, the JDK 1.1-equivalent tags I'm talking about are:
>     <struts:enumerate>
>     <struts:link1>
>     <struts:option1>
> 
> >
> > david
> 
> Craig McClanahan
>