Re: Newb taglib conceptual error: Missing tagclass for tag "dbgrid"

From:

Lew <lew@nospam.lewscanon.com>

Newsgroups:

comp.lang.java.programmer

Date:

Mon, 28 May 2007 21:25:33 -0400

Message-ID:

<YeWdnZwSZ66THMbbnZ2dnUVZ_v6tnZ2d@comcast.com>

angrybald...@gmail.com wrote:

Which means the web app can't locate the class for that tag. Imports
have nothing to do with it;

geoffalot wrote:

When you say "imports have nothing to do with it" - does that mean
even though a class is available via an import, it isn't necessarily
visible to the web application context?

That is correct. In fact, an "import" is necessarily not visible at runtime.

Bear in mind that "import" does not exist in the bytecode; it is a convenience
for the compiler only. What exists in the bytecode is a fully-qualified class
name every time.

At the (run-) time of first use, a class must be "brought in" to the JVM.
This is done through a ClassLoader. If the ClassLoader cannot find the class,
there is a runtime error. (Runtime errors can never have anything to do with
"import" because "import" is a compile-time concept.)

For a web app, the ClassLoader class path is as angrybaldguy described.

All "import" does is, in effect, a text translation of an unqualified class
name to a fully-qualified class name. It does nothing to guarantee runtime
availability of that fully-qualified class.

--
Lew