high level bits - sed to the rescue (or how to migrate from java.util.logging to org.slf4j)

sed to the rescue (or how to migrate from java.util.logging to org.slf4j)

2009-09-16 by fredrik java logging sed

I got the task to migrate all our code - some 100 classes - from standard JDK logging to the logging facade framework slf4j. (I am not sure if there are any real benefits from such a migration but the deploying organization has decided that this is the way to go so the best approach i to just look happy and accept. They also claim that there may be performance issues with the way we log now. It sounds a bit far-fetched to me....) A fast analysis of the task made me conclude that I needed to replace:

the import of java.util.logging.Logger with org.slf4j.*
the line constructing the Logger instance to use the slf4j LoggerFactory instead
.fine, .finer and .finest with .debug (for some reason .debug is the finest level in the slf4j API)
.warning with .warn
.severe with .error

A tedious work to do by hand. Thankfully there is a nice little unix command called sed that together with find does the trick almost perfectly. Here is the script I used:

#/bin/ksh
for file in `find . -name '*.java'`
do
 cleartool co -c "Changing log framework thingie." $file
 sed -e 's/java.util.logging.Logger/org.slf4j.*/' \
     -e 's/= Logger.getLogger/= LoggerFactory.getLogger/' \
     -e 's/.fine(/.debug(/'  \
     -e 's/.finer(/.debug(/' \
     -e 's/.warning(/.warn(/' \
     -e 's/.severe(/.error(/' \
     $file > $file.tmp
 mv $file.tmp $file
done

As you can see I also added a line to check out the file from Clearcase. If you are using CVS, subversion or even git (as any developer would given a free choice....) there is no need.

A couple of files failed to compile after the migration. Curly braces disappeared at the end of some classes and in one case the logger was instantiated on 2 lines instead of one but overall it worked nicely.

This way of working comes rather natural to me but I gather that not all developers think of the command line as a helpful tool and thus this blog post.

Old comments

2009-09-16Hardy Ferentschik

Sweet :) What would life be without sed, awk, find and grep. Any developer should have these tools in his toolbox.

2009-09-17Ceki

This post has been removed by the author.

2009-09-17Ceki

Have you looked at the SLF4J migrator? It accomplishes what you describe, except for the fine/finer/finest to debug mapping.

2009-09-17Fredrik Rubensson

Seems like my 10 line script was a bit better than the migrator then! Sometimes a few lines of unix scripting is all you need. But it is of course good that there are tools since many developers don't have a clue about unix.

h1ghlevelb1ts

sed to the rescue (or how to migrate from java.util.logging to org.slf4j)

Old comments