Re: [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