On Tue, 28 May 2002, Paul DuBois wrote:
> In an EL expression, does the identifier "null" return to the literal
> null value, or does it refer to a JSTL variable named "null".
"null" is a keyword in the EL, and it refers to null itself, not a
variable named "null"
> For example, if I want to explicitly set a variable to null, does this
> do it?
>
> <c:set var="myVar" value="${null}" />
Note that you can't really set a JSP scoped variable to null; you
can only remove it. <c:set> is specified to remove a variable when its
'value' attribute is null.
> I can find reference in the JSTL spec to testing whether the result of
> an expression is null or empty, but not how to *set* something null
> explicitly.
The behavior of <c:set> is discussed in section 4.3; its behavior on null
values is discussed in a section entitled, "Null & Error Handling".
> I guess a related question is this: You can use the "empty" operator
> to determine whether a value is null or empty; does "eq null" perform
> a test that is true *only* for null values?
Right - that's exactly it. empty tests for null, "", and a few other
things, primarily for the convenience of a page author who doesn't know
much about data types. You can still test directly against null using the
'null' keyword.
Shawn
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