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From Martin Cooper <mart...@apache.org>
Subject RE: Another bright idea, make "indexed" work with JSTL forEach and friends
Date Sat, 04 Jan 2003 21:36:31 GMT


On Sat, 4 Jan 2003, James Turner wrote:

> On Sat, 4 Jan 2003, Martin Cooper wrote:
>
> > If you want to do this, I'd rather see it happen in the html-el taglib
> > than the regular html taglib. Struts-EL already depends on
> > JSTL, and is
> > designed to work in cooperation with it, so it's a much more
> > natural fit
> > than trying to sneak JSTL functionality into the regular tags.
>
> I mildly disagree.  EL is to allow struts HTML tags to use EL syntax.

Yes. And why would you want to do that? Because you're already using JSTL
tags in your pages, and you want the two to work together.

> This deals with letting the standard tags find JSTL looping constructs.

Yes. And why would you want to do that? Because you're already using JSTL
tags in your pages, and you want the two to work together.

Notice the remarkable similarity in the two reasons for using these pieces
of functionality? ;-)

That's why I think your suggestion fits much better in Struts-EL than in
the Struts core. Once we require Servlets 2.3 / JSP 1.2 for Struts, then
I'm all for having this in the core, along with the rest of Struts-EL.
Prior to that, I just don't like the idea of muddying the core html taglib
with references to JSTL, especially when you have to do it all through
reflection.

--
Martin Cooper


> As is, you can "*almost* entirely eliminate all the Struts tags except
> for the HTML tags in favor of JSTL substitutes, since only the HTML tags
> deal with things like actions.  By implementing this, we can eliminate
> having to use the logic taglibs at all.  And the change is pretty darn
> innocuous, here's the revisted code from BaseHandlerTag, which works
> very nicely.  Note that I'm not even referencing org.apache stuff.  And
> the JSTL stuff is only ever invoked if it fails to find the Iterate tag.
>
> One thing I'm considering is caching the classes and methods so that the
> reflection doesn't need to happen on every invokation.
>
>     protected void prepareIndex(StringBuffer handlers, String name)
> throws JspException {
> 	int index = 0;
> 	boolean found = false;
>
>         // look for outer iterate tag
>         IterateTag iterateTag = (IterateTag) findAncestorWithClass(this,
> IterateTag.class);
> 	// Look for JSTL loops
> 	if (iterateTag == null) {
> 	    try {
> 		Class loopClass =
> Class.forName("javax.servlet.jsp.jstl.core.LoopTagSupport");
> 		Object loopTag = findAncestorWithClass(this, loopClass);
> 		if (loopTag != null) {
> 		    Method getStatus =
> 			loopClass.getDeclaredMethod("getLoopStatus",
> null);
> 		    Object status = getStatus.invoke(loopTag, null);
> 		    Class statusClass =
>
> Class.forName("javax.servlet.jsp.jstl.core.LoopTagStatus");
> 		    Method getIndex =
> 			statusClass.getDeclaredMethod("getIndex", null);
> 		    Integer ind = (Integer) getIndex.invoke(status,
> null);
> 		    index = ind.intValue();
> 		    found = true;
> 		}
> 	    }
> 	    catch (ClassNotFoundException ex) {}
> 	    catch (NoSuchMethodException ex) {}
> 	    catch (IllegalAccessException ex) {}
> 	    catch (IllegalArgumentException ex) {}
> 	    catch (InvocationTargetException ex) {}
> 	    catch (NullPointerException ex) {}
> 	    catch (ExceptionInInitializerError ex) {}
> 	} else {
> 	    index = iterateTag.getIndex();
> 	    found = true;
> 	}
>         if (!found) {
>             // this tag should only be nested in iteratetag, if it's
> not, throw exception
>             JspException e = new
> JspException(messages.getMessage("indexed.noEnclosingIterate"));
>             RequestUtils.saveException(pageContext, e);
>             throw e;
>         }
>         if (name != null)
>             handlers.append(name);
>         handlers.append("[");
>         handlers.append(index);
>         handlers.append("]");
>         if (name != null)
>             handlers.append(".");
>     }
>
>
>
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>
>


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