[slf4j-dev] Context for getLogger()

[Fred]

On Fri, Jul 2, 2010 at 7:27 AM, Thorsten Möller
<Thorsten.Moeller at unibas.ch> wrote:
> Hi Fred,
>
> coming back to your posting, I have some comments/questions - inlined
> ...
>
>
> On Monday, June 28, 2010 10:08 PM [GMT+1=CET],
> Fred <phreed at gmail.com> wrote (with possible deletions):
>
>> I have been modifying slf4j for use on android.
>> Beginning with the slf4j-android sub-project, I am adding in
>> a context provider to record, forward, combine, filter and otherwise
>> manage the log.
>> In order to do this getLogger needs to know the current context.
>> To work around this I have added a context parameter.
>>
>> e.g.
>> import android.content.Context;
>> import android.graphics.Matrix;
>> import org.slf4j.Logger;
>> import org.slf4j.LoggerFactory;
>>
>> public class Sample implements Cloneable {
>>
>> private Sample(Context context) {
>> _log = LoggerFactory.getLogger(Sample.class, context);
>> ...
>>
>> I can provide more detail if this is not clear.
> Indeed  it is not clear. Could you describe a use case illustrating why
> this would be required. And maybe other options to achieve the same.

The following example presumes some knowledge of the android environment.
Consider a Log ContentProvider (basically a log server).
In order to communicate with any ContentProvider a ContentResolver is required.
A ContentResolver is obtained for a particular Context.
The relevant Context object is not a global variable.
Thus in order for the 'logger.info("sample message");'  to work the logger must
have access to the Context (or a ContentReceiver).

The following attempts to explain in a non-android specific way.
Suppose that you have a logging service.
You connect to this logging service and wish to have that connection
available within some (deeply nested) subroutine but
you don't (can't) have global variables.
No problem, just keep the connection as a property of the logger object.
In other words put the connection (and anything like it) into a
context object which is a property of the logger.
The problem is I don't see a way to associate a context
implementation object  with a logger.

I would expect there to be ILogger and IContext interfaces which would be
implemented via AndroidLogger and AndroidContext classes.
The ILogger.java and AndroidLogger.java files exist (but ILogger.java
is called Logger.java) but no IContext.java.
I have made a patch to add IContext.java and AndroidContext.java.

If that still isn't clear I can post the code.
But the code won't help unless you understand the problem.
The problem is that the current implementation presumes certain
context information is available as global variables, which
aren't available when communicating between android applications.


>> What I want to know is if this is the best way do deal with the
>> problem?
> Since it is not clear to me what the actual problem is I would first try
> to understand it.
>
>> In order to get this to work I have added some android specific stuff
>> to the api/contract.
>> The presumption seems to be that certain information is in some
>> global variable. This doesn't seem quite right.
>> What I am wondering is if there shouldn't be some generalization of
>> context for slf4j.
> This can all be answered if we see the complete picture.
>
> Cheers,
> Thorsten
>
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