Hmm... You are correct that this is the behavior described by the real spec.
Even though the JSP reference card on Sun's website clearly state a
different behavior.
http://java.sun.com/products/jsp/syntax/2.0/syntaxref2027.html#8865
I guest we can only blame the reference card. :-)
On Tue, Jun 17, 2008 at 1:29 PM, Scott Ferguson [EMAIL PROTECTED] wrote:
On Jun 17, 2008, at 12:42 PM, Hacking Bear wrote:
See in the discussion link
You need to address the section I quoted from the spec. It is extremely
clear:
5. If the object is not found in the specified scope and neither class
nor beanName are
give, a java.lang.InstantiationException shall occur. This completes
the processing of this
jsp:useBean action.
There is zero ambiguity in that rule.
However, you may be right that the tag lib spec allows the use of type
attribute only. In
http://java.sun.com/products/jsp/tags/11/syntaxref11.fm14.html , it first
says If the Bean does not exist, jsp:useBean instantiates it from a class
or serialized template. and then on the attribute description:
That page is not part of the spec. Also, it appears to be for JSP 1.1.
Here are some relevant snippets from the JSP 2.1 spec. However, as far as I
know the sections haven't changed for either 2.0 or 2.1 versions:
*(section JSP 5.1, jsp:useBean)*
It is also possible to use this action to give a local name to an object
defined elsewhere, as in another JSP page or in a servlet. This can be done
by using the type attribute and not providing class or beanName attributes.
You're quoting from non-normative explanatory/example text. The language
is looser. The Semantics section is the precisely defined, normative
section of the spec.
In the final example, the object should have been present in the session.
If so, it is given the local name wombat with WombatType. A
ClassCastException may be raised if the object is of the wrong class, and an
InstantiationException may be raised if the object is not defined.
That doesn't contradict rule #5 at all. It says an InstantiationException
will be raised if the object isn't defined. (And since it's from
explanatory text, the language is looser than the language in the Semantics
section, i.e. the correct word is shall, not may.)
jsp:useBean id=wombat type=my.WombatType scope=session/
And for all practical purposes, useBean should allow setting the variable
to null because many classes are bean-like and not strict JavaBean and it
is also harder to tell if it is an valid bean or an empty bean.
Should has nothing to do with specifications. There is only does and
does not. There is no should. (Well, ignoring optional, but highly
recommended sections of a spec, which doesn't apply in this case.)
-- Scott
On Tue, Jun 17, 2008 at 12:09 PM, Scott Ferguson [EMAIL PROTECTED] wrote:
On Jun 17, 2008, at 11:51 AM, Hacking Bear wrote:
Hi,
As we are discussing some other issues, we found a potential serious
problem with jsp:useBean. Basically, if useBean only has the type parameter
but not the class/bean parameters, the resin server will fail because it
does not know what to instantiate, contrary to the spec.
!-- should set foo to null but fail instead. --
jsp:useBean id=foo type=java.lang.String scope=request/
How is that contrary to the spec?
JSP.5.1
5. If the object is not found in the specified scope and neither class
or beanName
are given, a java.lang.InstantiationException shall occur. This
completes the
processing of thisjsp:useBean action.
-- Scott
For the full discussion of the bug and the JSP spec, see
http://www.jetbrains.net/jira/browse/IDEA-18405
The strange thing is that Tomcat behaves the same. So I wonder if this is
a bug or a legacy problem for the servers due to confusing descriptions in
earlier JSP spec?
Please enlighten me!
Thanks
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