[9] RFR: 8177136: Caller sensitive method System.getLogger should specify what happens if there is no caller on the stack.

[David Holmes]

Hi Daniel,

On 22/03/2017 4:41 AM, Daniel Fuchs wrote:
> Hi Brent,
>
> Here is an updated webrev that incorporates your feedback:
>
> http://cr.openjdk.java.net/~dfuchs/webrev_8177136/webrev.02

You could move all the detail to the @implSpec method as a clarification 
on the use of the caller e.g.:

      * @implSpec
      * Instances returned by this method route messages to loggers
      * obtained by calling {@link LoggerFinder#getLogger(java.lang.String,
      * java.lang.reflect.Module) LoggerFinder.getLogger(name, module)}, 
where
      * {@code module} is the caller's module. In cases where there is
      * no Java caller on the stack (e.g when called directly from a JNI
      * attached thread) an IllegalCallerException is thrown. To obtain
      * a logger in such a context ...

then just:

    * @throws IllegalCallerException if there is no {@linkplain
    *         StackWalker#getCallerClass() caller} frame, i.e. this method
      *         is called from JNI and there is no Java frame on the stack.

Up to you.

Thanks,
David

> Thanks!
>
> -- daniel
>
> On 21/03/2017 18:21, Brent Christian wrote:
>> Hi, Daniel
>>
>> I think the new @throws tag gives a good explanation of the situation,
>> with instructions for someone wanting to get a System.Logger from JNI.
>>
>> To nitpick on style, it's maybe on the long side for an @throws -
>> perhaps consider a slightly more concise version:
>>
>>      * @throws IllegalCallerException if there is no {@linkplain
>>      *         StackWalker#getCallerClass() caller} frame, i.e.
>>      *         this method is called from JNI
>>      *         and there is no Java frame on the stack.<br>
>>      *         To obtain a logger in such a context, the caller
>>      *         should either use an auxiliary class that will implicitly
>>      *         be identified as the caller, or use the system {@link
>>      *         LoggerFinder#getLoggerFinder() LoggerFinder} to
>>      *         obtain a logger. Note that doing the latter
>>      *         may eagerly initialize the underlying logging
>>      *         system.
>>
>> Thanks,
>> -Brent
>>
>> On 3/21/17 5:44 AM, Daniel Fuchs wrote:
>>> Hi,
>>>
>>> Please find below an updated patch for:
>>>
>>> 8177136: Caller sensitive method System.getLogger should  specify
>>>          what happens if there is no caller on the stack.
>>> https://bugs.openjdk.java.net/browse/JDK-8177136
>>>
>>> webrev:
>>> http://cr.openjdk.java.net/~dfuchs/webrev_8177136/webrev.01
>>>
>>> System.getLogger(name) and System.getLogger(name, resourceBundle)
>>> are specified to call LoggerFinder to obtain a logger, which requires
>>> the module of the caller class.
>>> When there is no java frame on the stack, then the caller information
>>> cannot be obtained and there is not enough context to know which module
>>> would be appropriate.
>>> The proposal is to throw IllegalCallerException - which is the exception
>>> that StackWalker::getCallerClass will throw if called by
>>> System::getLogger in this case.
>>>
>>> This RFR follows the discussion started here:
>>> http://mail.openjdk.java.net/pipermail/core-libs-dev/2017-March/046868.html
>>>
>>>
>>>
>>> best regards,
>>>
>>> -- daniel
>