[logback-user] Marker

Ceki Gulcu listid at qos.ch
Mon Oct 20 14:19:27 CEST 2008

ekkehard wrote:
> Ceki Gulcu schrieb:
>> Hello Ekke,
>> What is it that you are trying to accomplish, in plain English?
> My Logger objects are in each class
> but I also want to know the OSGI Bundle name from where the log entry comes
> and - optional - the OSGI Service names from where the event happened

What is the relation between bundles and services? For example, is it true to 
say that at time t0, bundle b0 offers services s00, s01, s02, bundle b1 offers 
services s10 and s11, while at a later time t1, bundle b0 offers services s00 
and bundle b1 offers services s10, s11 and s12?

If the above is true, you could create a marker named B0, S00, S01, S02, B1, S10 
and S11. For example, with the following code

   Marker B0 = MarkerFactory.getMarker("B0");
   Marker B1 = MarkerFactory.getMarker("B1");
   Marker S00 = MarkerFactory.getMarker("S00");
   Marker S11 = MarkerFactory.getMarker("S11");

Once the markers are created, you can organize them in a graph, for example as


You can iterate through the references contained in a marker by calling the 
iterator() method. Thus, if you wish to print the name of a bundle and all the 
services it contains, you would print the name of the bundle marker and iterate 
through its service markers (and print their names).

If at time t1 the list of services changes, then you can add or remove 
references to service markers from the bundler markers as appropriate.

If you are using the default marker factory, keep in mind, in the two lines 
below, that x0 and x1 refer to the same marker object named X:

  Marker x0 = MarkerFactory.getMarker("X");
  marker x1 = MarkerFactory.getMarker("X");

My point is that, the default marker factory cannot deal with the same bundle 
markers having two different facets simultaneously depending on the context. 
For example, you can't assume that the same bundles offers s0 for one request 
and offers s1 but not s0 for a another request occurring at the same time. This 
may be a totally obvious and acceptable restriction to you. I don't know OSGI 
well enough to tell in advance.

Alternatively, you could implement your own Marker implementation and your own 
marker factory, allowing you to check if a marker is a "bundle marker" or a 
"service marker" or some other type. You could iterate only though bundle 
markers or only through service markers. As long as the markers you pass to 
logback implement the org.slf4j.Marker interface, logback does not care.


Ceki Gülcü
Logback: The reliable, generic, fast and flexible logging framework for Java.

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