RFR: 7148497: javax.management.MBeanAttributeInfo.hashCode throws NullPointerException

[Frederic Parain]

Karen,

As far as I can tell, getDescriptor() never returns null.

In the javax.management package, getDescriptor() calls
ImmutableDescriptor.nonNullDescriptor(descriptor).clone()
which returns a reference to a singleton empty Descriptor
instance if the descriptor field is null.

The getDescriptor() method is redefined in some classes of
the javax.management.modelmbean package, but these implementations
never return null either.

So, unless I missed some code, it is safe to use getDescriptor()
without null check.

Fred

On 4/13/12 3:54 PM, Karen Kinnear wrote:
> Frederic,
>
> Looks good. And I like the refactoring.
>
> A question - does the Descriptor field have the same potential for being null? e.g.
> in MBeanFeatureInfo.java new line 160 - do you need to check getDescriptor() == null as well?
> in MBeanConstructorinfo.java line 197, do you need the alternative null checking?
> MBeanAttributeInfo.java line 293?
> (there may be other lines, I didn't do a thorough search)
>
> thanks,
> Karen
>
>
>
> On Apr 13, 2012, at 9:01 AM, Staffan Larsen wrote:
>
>> This is much easier to read!
>>
>> In MBeanFeatureInfo.hasSameName() this check is not needed:
>>
>> 274         if(info.getName() == null) {
>> 275            return false;
>> 276         }
>>
>> since String.equals() with a null argument works as expected (return false). The same is true for the implementation in hasSameDescription().
>>
>> When calling hasSameName() and hasSameDescription() the "this." is not needed, but perhaps using it makes the intent clearer?
>>
>> Thanks,
>> /Staffan
>>
>>
>>
>>
>> On 13 apr 2012, at 14:45, Frederic Parain wrote:
>>
>>> Thanks Staffan and Dmitry for your feedback,
>>> here's a new webrev with a refactored code for
>>> name and descriptions fields which are common to
>>> most MBean*Info classes:
>>>
>>> http://cr.openjdk.java.net/~fparain/7148497/webrev.01/
>>>
>>> Thanks,
>>>
>>> Fred
>>>
>>> On 4/12/12 8:18 AM, Dmitry Samersoff wrote:
>>>> Frederic,
>>>>
>>>> I'm second to Staffan.
>>>>
>>>> Looks good to me but would prefer to have it refactored, e.g. create a
>>>> method equalOrNull();
>>>>
>>>> -Dmitry
>>>>
>>>>
>>>> On 2012-04-10 18:33, Staffan Larsen wrote:
>>>>> Looks good! (Although I wish there was a better way to write code like
>>>>> this).
>>>>>
>>>>> /Staffan
>>>>>
>>>>> On 10 apr 2012, at 15:50, Frederic Parain wrote:
>>>>>
>>>>>> Greetings,
>>>>>>
>>>>>> This is a request for review for CR
>>>>>> 7148497: javax.management.MBeanAttributeInfo.hashCode throws
>>>>>> NullPointerException
>>>>>> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7148497
>>>>>>
>>>>>> Even if the initial CR only refers to MBeanAttributeInfo.hashCode(),
>>>>>> the problem is not limited to the MBeanAttributeInfo.hashCode(), but
>>>>>> is common to all javax.management.MBean*Info classes:
>>>>>> MBeanAttributeInfo, MBeanConstructorInfo, MBeanFeatureInfo,
>>>>>> MBeanInfo, MBeanNotificationInfo, MBeanOperationInfo and
>>>>>> MBeanParameterInfo.
>>>>>>
>>>>>> The root cause of the problem is that these classes can be
>>>>>> instantiated with some null fields (mainly, but not limited to, the
>>>>>> name and type fields), and these fields are dereferenced
>>>>>> unconditionally in some methods. Unconditional dereferencing is used
>>>>>> in the hashCode method but also in the equals() method.
>>>>>>
>>>>>> The proposed fix improves implementation of equals() and hashCode()
>>>>>> method to handle cases where some fields are null without throwing
>>>>>> a NPE.
>>>>>>
>>>>>> Webrev:
>>>>>> http://cr.openjdk.java.net/~fparain/7148497/webrev.00/
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> Fred
>>>>>>
>>>>>> --
>>>>>> Frederic Parain - Oracle
>>>>>> Grenoble Engineering Center - France
>>>>>> Phone: +33 4 76 18 81 17
>>>>>> Email: Frederic.Parain at oracle.com
>>>>>>
>>>>>
>>>>
>>>>
>>>
>>> --
>>> Frederic Parain - Oracle
>>> Grenoble Engineering Center - France
>>> Phone: +33 4 76 18 81 17
>>> Email: Frederic.Parain at oracle.com
>>>
>>
>

-- 
Frederic Parain - Oracle
Grenoble Engineering Center - France
Phone: +33 4 76 18 81 17
Email: Frederic.Parain at oracle.com